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searching-for-mercury · 7 years ago

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Voltron - Klance - Fake BF

All I Want for Christmas is a (Fake) Boyfriend

Summary: A while ago, in a fit of anger, Keith told his mom he had a boyfriend. Did he actually have a boyfriend? No. Did he care? Also no. At least, not until his mom, months later, tells him to bring his supposed boyfriend over for the holidays. Not wanting to admit he didn't have one, Keith asks around for someone to play the role and who agrees to play the part? The annoying guy from his Lit class.

(AO3)

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Chapter One

Two weeks into December should have been the time to breathe easy, where the only stress ought to have been in preparation for and during finals week. The flurry of books and exams, papers and projects, all crammed into the last week of the semester. Long hours of studying could finally turn into hours of caught up sleep, of eating full meals at a normal pace. Dishes piled haphazardly in the sink could be washed, laundry done, and, of course, packing up the car to drive home for the holidays.

But that was exactly Keith's problem: the holidays. He'd promised his mom he would drive the several hours it took to get there and stay a couple days for Christmas. He'd done it before and he'd do it again, gladly, if it hadn't been for one little thing -- his mom told him to bring his boyfriend.

He didn't have a boyfriend.

A couple years back, he'd come out to his parents as gay and his dad was far more supportive than Keith had ever dreamt. But his mom? His mom was...doubtful. He didn't understand it and his dad tried talking to him about it before, but the point remained: his mom didn't believe he was actually gay. Maybe it had something to do with how, after his parents divorced, Keith had gone to live with his dad and his mom felt left out. Maybe she just couldn't wrap her head around the idea, maybe she needed time. There were a gazillion possibilities and he only thought about them after he got mad.

In a fit of fury, he'd told her he was going steady with a guy from school and things were great; his relationship, his life, everything! He'd wanted to rub it in her face that he was gay and doing just fine! Better than fine!

Time had passed and he'd sort of forgot about his fake boyfriend until about an hour ago when his mom called. What was he going to do? He either needed to find a boyfriend or come clean to his mom and just feel the "I knew it" vibes that would surely radiate from her the entire time he was there.

No, that wasn't an option. He had to think of something else.

So he pulled out his phone and typed out something, thought about it, erased some words and retyped a few, and then sent it to two people. As soon as he hit send, however, he felt regret surge up from the depths of his stomach. His thumping heart didn't help any, either.

It was a stupid idea, but that only made sense because he was a stupid person. Stupid, stupid, stupid--

His phone chirped at him. Someone had responded.

Unfortunately, it was Allura with a solid, "No, sorry, I don't think I know anyone who could help! Maybe try Pidge?"

But he was way ahead of her. He'd already texted Pidge and he was really hoping she had a better answer. She was probably at work, though, so Keith went around trying to keep busy.

Lists were made, vacuuming was done, and he even got around to cleaning the inside of his shower. It was when he was in the middle of making dinner, staring at the tiles on the wall and wondering if he should get a haircut before or after his family visit, that the fateful chime of his phone sounded.

"Yeah, I know a guy," she wrote.

Keith hummed with impatience. Couldn't she have just figured he wanted more details?

"Great, can I have his number?" he typed back. Honestly, was it that hard to do?

"No."

Apparently so.

After a bunch of typing back and forth, Keith was left with a sort of empty, nervous feeling that started in his feet, for some reason, and a date. Well, not a date date, just an appointment kind of date. Ugh, even in his head it sounded stupid. A meeting time. There.

He would meet with this mystery person the next day in the park by Best Buy. It was where Pidge worked. She'd always been really into technology and picking apart computers. When they were younger, they would go find unfinished homes to sneak onto, just so she could peer into the walls and see how the wiring was laid out. That and play space pirates. Their echoes in those empty homes had always made everything feel more dramatic, exciting. They'd stomp down wooden staircases, crawl through open cabinetry, and have epic duels out on the windy, dirt-filled backyards, under dark clouds and the setting sun.

But the wiring always came first. She technically worked at the Geek Squad that was a part of the Best Buy, but it was only a temporary thing until she finished her degree. Keith could never quite remember what it was, but it sounded important. Then again, a master's degree in anything always sounded important. Maybe it was engineering -- but he could have sworn there were more words to it.

Regardless, he showed up the next day at three in the afternoon, holding a coffee in one hand and his phone in the other, at the park she'd told him about. He was early. Pidge, however, was not, as she wrote in her text message.

"Sorry, running late for work. Can you meet him alone?"

Keith eyed the store from the wooden bench he'd just settled down on. If they sold binoculars there, they'd be some weird, hi-tech stuff. He narrowed his eyes just in case. If he didn't know Pidge any better, he'd have told himself it was a bit of a stretch, to think she'd set this all up only to spy on them from afar.

He was halfway done writing, "How am I supposed to meet him when I don't know what he looks like," when someone stopped walking right in front of him.

The guy was wearing real snazzy boat shoes and straight-cut jeans that were cuffed at the ankle. Keith looked up to find a striped shirt under a blazer-style jacket and then the face that put it all together. He wasn't sure what he'd been expecting, but it wasn't him.

"Hey there, you're Keith, right?" the guy said. He had a smile whiter than the snow they were expecting later that week. It was a smile Keith had seen before, but never directed at him.

"Uh, yeah," he replied.

"We take a class together, don't we? Your face looks familiar."

Keith nodded and gestured for him to sit down. "Modern Literature," he replied.

He wasn't sure who he'd been expecting, but it sure wasn't the guy who held up his Lit class almost every single time during class discussions, talking about everything other than the actual topic. Keith wasn't much of a talker during those classes, he was more interested in his science classes, but this guy was the reason their class never got out on time. Five, ten minutes over their intended class period and the only thing on Keith's mind was murder. It had been his last class of the day -- he just wanted to go home.

"You're the guy who doesn't like poetry!" the guy exclaimed.

Keith was blanking on his name. Something with an L. Louis? Lars? La-- "You're Lance, right?" he asked, hoping that if any deity in the world existed, it would hear his prayers and tell him he was right.

"Yup!" he said and gave another one of those smiles. He was always chatting up the girls in the class -- he even went so far as to compliment the teacher on her hair, though Keith was pretty sure that was only to get an extension on a paper. The point was, why was he there? Pidge had explained everything to him all proper, right?

"Did Pidge, uh, explain things?" Keith asked. He could feel his face heat up, but he was really hoping it was one of those times that didn't show. "About what I was asking for?"

"Oh, right, yeah dude, no worries," Lance said. "You're looking for a pretend boyfriend, right?"

God, it felt so...pitiful, hearing it said out loud like that. He wasn't starved for a relationship or anything, he just had something to prove.

"And you're fine with acting the part?" Keith asked. He hadn't even begun to start questioning if he, himself, was okay with acting the other part. With Lance.

"Yeah, I mean, I figured we could talk about it some more," Lance replied with a shrug.

It still didn't make any sense. Lance was okay with acting the part of a boyfriend for another boy. "Are you gay?" he blurted out. Well. That just happened.

Lance's eyebrows went way up. They looked a little too neat to be natural. "Bisexual, actually," he said. "But no worries, you set the rules!"

"Rules?" he said before it caught up to him. Oh. Oh. "Uh." He should have probably thought things out a little more. It sounded much worse than what he'd actually intended. "How about I explain the situation first?"

Lance nodded and Keith relaxed into a retelling of everything that had happened to land him in such hot water. It made him feel better, though, explaining everything. Made him seem a little less creepy, maybe. Hopefully.

In the end, Keith agreed to buy Lance Taco Bell every Wednesday of the next semester in return for everything playing a pretend boyfriend entailed. It felt a lot better than paying him with money (though he had offered), but not by much. He definitely wondered why Lance was so easy-going about the whole deal, but he felt it kind of rude to ask.

Instead he went, "What about your own family? Don't they want you back for Christmas?"

Lance just scratched at his chin and said, "Don't worry about it. I don't have any plans."

Hm. It wasn't really an answer, but they weren't close enough to where Keith could just push on through with more persistent questioning. Why didn't he have plans? Was there family drama? Did he not celebrate Christmas?

Not knowing what to say, Keith just nodded and fiddled with the plastic lid on his now-empty coffee cup. He kind of wished it were still at least a little bit of the way full -- he could always sip on it during the awkward pauses.

"Can I get your number?" Lance asked. "I might have some questions before the big day. Or night. Or, well, all of that."

Why was Keith's face getting all warm? There was absolutely no reason for his face to be heating up. It was December. The temperature was probably close to whatever zero meant. "Sure," he said and pulled out his phone. It was sleek silver thing that reacted a little too eager to his touch, encased in a striped red case.

Lance's was blue with a crack in one of the corners.

"Then I'll see you next week!" Lance said, bouncing off the bench. He laughed. "Taco Bell for a whole semester. Sweet."

But before Keith could reply with, "It's really not that big of a deal," because Taco Bell was cheap and also garbage, Lance was striding away on those ridiculously long legs of his. There was a little wave involved, but Keith chose to nod instead.

A whole week, huh? Yeah, an entire week to over-think things and regret all the decisions he'd ever made to land him in such a situation. Perfect.

~*~

The picking up of Lance McClain, as it was so typed in his phone, was a relatively easy thing. In theory. So Keith didn't understand why he was parked in the parking lot of one of the school dorms, slouched in his seat, listening to Billy Joel's "It's Still Rock and Roll to Me." It was a good song and one of the few stations that would stay good during the whole four hours it would take to drive to his mom's house. It would change, naturally, but it just sort of fizzed out and then it was just solid rock music.

But he didn't understand why he was sitting there, focusing on the lyrics, while Lance was doing whatever it was that was taking him so long to get downstairs and in his car. He'd texted him half an hour ago when he was leaving. He'd given him a whole week's notice.

A small voice in his head was scratching at the possibility that Lance changed his mind and this was his way of canceling on him. But he chose to ignore that voice in favor of Billy Joel's more upbeat tone and wonder what 'white wall tires' could mean. He would have pulled out his phone to look it up, but he was afraid that if he did that, he'd also send Lance a stream of unpleasant, nagging texts.

He really didn't want to be that person. He'd been that person in high school; he sure hoped he wasn't still.

When Lance finally did stroll out of the double doors to the building -- and that's exactly what he did, stroll -- he was carrying two large duffel bags and a backpack. It was four hours away, not four weeks. And they were only staying for three days. Three.

"Holy mother of god," Keith said. He was incredibly glad he was still alone in his car.

After popping the trunk and grabbing the keys from the ignition (he'd locked himself out once and never again. Never. Again.), he hopped out to help rearrange some of his stuff to make room.

"You read my text right...right?" Keith asked. "It's only three days."

"Three days can mean a lot," Lance replied, swinging his first bag in. The second went in much more gently. His backpack he put in the backseat. "I like to be prepared."

"For what, an invasion of zombies?" Keith muttered.

Unfortunately, Lance heard. "Hey man, you never know. Doesn't have to be zombies. Could be aliens." He waggled his eyebrows.

Keith only rolled his eyes and got back in his seat. Lance was still pulling on his seatbelt by the time he pulled out of the parking spot.

"Is that what took you so long?" Keith ventured to ask. Hey, he hadn't sent the long stream of texts, but he wasn't about to just let it slide.

"Yeah, I was making sure I grabbed everything," Lance replied. He was staring out the window at the passing buildings. "Like I said, gotta be prepared."

"It's a house in the mountains," Keith replied. "Doesn't exactly scream dangerous."

"Having never been there, I couldn't take my chances," Lance shot back.

Keith sighed, deep and heavy. Whatever, they were in the car, on their way -- that's all that mattered.

It grew quiet as Keith navigated their way through the town, but picked up again once they hit the highway.

"Winter kind of bums me out," Lance said. "All the dead trees and frozen ground. I want summer! And the beach! Man, what I would give to go swimming just about now." "Be my guest, there's a lake you can hike to near my mom's." It was probably frozen several inches thick, but why should that stop him?

"You know what I mean." Keith didn't have to be looking at him -- he could hear the scowl in Lance's voice.

"Hm, then you picked the wrong state to be in," Keith replied. "We, my friend, are land-locked."

"You can still go swimming, though," Lance pointed out. "And there's actually a lot more to do here than by a beach. But still, can't deny the wonderful feeling of stretching out and soaking up the sun."

Keith couldn't relate. He had skin that burned and blistered if he dared go out without sunscreen. He always had to carry around the smelly stuff, just in case it wore off. Higher elevations meant being closer to the flaming orb in the sky that turned his skin to a peeling, burning mess.

"Anyways, I've got a question," Lance said. "What are we going to tell your mom when we get there?"

Keith switched lanes -- there was a left lane for a reason, people. "What do you mean?"

"You know, if she asks us how we met," Lance said. "Just a basic story."

It was a question Keith had been thinking about the entire week. He just wasn't good with story-making. Meeting in a bar sounded kind of seedy, but would his mom believe something too picturesque?

"How about our friends hooked us up?" Keith offered. It was pretty much the truth.

"That's so boring!" Lance said, sitting up a little straighter. "Couldn't I have picked you up somewhere? Like, where do you work?"

"A Call Center."

"Oh. Never mind. I thought if you worked in a restaurant, I could have been enamored or something and just routinely had dinner every time you had a shift," Lance said.

"Kind of stalker-y," Keith pointed out.

"Not if you found it endearing!"

"But I don't."

"You could pretend. That's the whole point of this operation," Lance said, huffing. He slid down in his seat.

Keith rolled his eyes. He didn't understand what was so important about what should be a simple story. But Lance was doing him a huge favor, even if badly made fake Mexican food was part of the payment plan. "We...met at school," Keith said. "Freshmen orientation. But we didn't start dating right away, we just started out as friends."

He could feel Lance's eyes on him, but he remained focused on the road. Cars were slowing down, so either a cop was up front or they were hitting some traffic. He glanced down at the speedometer; it was legal.

"Not bad," Lance finally said. "Can I still be the one who asked you out?"

That time, Keith looked over. "Uh, sure?" he said.

Another glance at Lance -- he looked a little pleased, a small smile curled up on his face. It reminded Keith of a cat an old neighbor had owned; was a tawny brown, fluffy thing with big gold eyes and dark paws. He'd seen it in the window every time he left to go catch the bus for school.

Traffic picked up again and the radio started switching about an hour into their ride. Dark trees rolled by, though not very tall or thick. The road narrowed into two lanes, each in different directions. The curves around the mountainsides always used to make his dad nervous and they always knew when it got bad because their car would slow to a crawl.

"I've got another question," Lance said all of a sudden. He reached out to lower the volume.

"Shoot."

But Lance fidgeted with his fingers a bit before responding. "How far exactly do we go to prove we're in a relationship?" he asked. "Like, what's appropriate? Do we hug? Kiss?"

"Uh," Keith said. He kind of wished they'd discussed it earlier, when he wasn't driving past great big cliffs and around tight turns. "I'm down for whatever you are. I guess."

"Cool," Lance replied. "By the way, can we stop by somewhere eventually? I could kill for a coffee or some water."

Somewhere. Right.

"You couldn't have asked when we were driving past all those gas stations?" Keith asked.

"I wasn't thirsty then."

"I swear to god," Keith grumbled.

"Hey man, I didn't say right now. I just said it for when you, you know, see a good spot," Lance said. "Eventually."

Was he going to strangle him? Probably not. But throwing him off the mountain did seem rather tempting. If they weren't stuck behind a minivan that had absolutely no business being there, he might have actually done it.

Instead, he turned the music up again and continued driving to safer, less precipitous places. If he'd been driving with an actual boyfriend, maybe he wouldn't be having such a hollow, sour feeling in his stomach. Maybe he wouldn't be kicking his own ass for not making up an excuse to not go. A lot of maybes roamed around in his head, but nothing to make them settle, no tiny, wriggling bit of hope for a good time.

"There!"

Keith nearly flew out of his seat. "Jesus," he hissed.

"There's a stop coming up!" Lance said, pointing out his window at a sign that passed by.

"Any reason to shout it?" Keith asked. Luckily, he'd stayed in his lane. There was only a semi-truck in the other one. His heart was pounding and he'd definitely jerked the wheel. "Have you never ridden in a car before? Don't scare the driver. He is responsible for your safety."

"Sorry," Lance said, but Keith didn't believe an ounce of it. "But there's a gas station coming up with a McDonalds and I think a Subway."

"You hungry?" Keith asked.

"A little, but you said we'd be eating dinner at your mom's," Lance replied. "But I'm thirsty and these legs of mine could use some stretching."

Keith tried not to look at those legs of his.

As he was turning into the area where the buildings sat, all nestled together, he asked, "So what'll it be?"

"Hm, well," Lance said. "Let's try out the gas station first and if their drinks are expensive, we'll go through the drive-thru at McDonalds. Nothing beats that dollar menu."

Keith wanted to ask, then why bother with the gas station at all? He breathed in, breathed out. Whatever, Lance had his reasons. Keith didn't need to understand or ask about them.

He pulled the car into the parking lot, shifted into park, and went to unbuckle. Only he didn't get that far because suddenly Lance grabbed his face and kissed him. Not fully on the mouth, but enough.

"What the hell?!" Keith sputtered, pulling back. His face was on fire. His face was on fire and he didn't care, but he did, and he couldn't help it, but he wished he could.

"Yup, thought so," Lance replied.

For once, Keith couldn't form a response fast enough.

"We should practice kissing so that doesn't happen in front of your mom," Lance said.

"Okay, first off -- you should have just said that before you went all, all... And secondly, I probably wouldn't react that way if you'd warned me about it," Keith said. Both points were basically the same thing, but his brain was still a little fried. "Who just goes around kissing people like that?"

Lance scratched at his chin, looking a little sheepish. His shoulders tucked in a bit, like he wanted to make himself smaller. "Sorry," he said. It was a believable apology, that time. Hit all the right kinds of apologetic tones.

Keith only nodded, frowning out the windshield at the brown bricks that made up the gas station. He kind of wished real life had a little angel and devil to talk to on each shoulder. Maybe not the devil, he did plenty of things he regretted enough on his own, but the angel might've helped. At the very least, it could have told him if it was bad to feel kind of excited about kissing the boy sitting in his car. At the thought of more kissing.

Then again, most Bible-pushers said being gay was a sin, so maybe the angel would just berate him for that.

"Keith?"

He jerked back into their world. "Right," he said. "Practice. Um. Sure, but it'll probably be weird."

And it was weird. But also nice. It was a lot nicer when Lance actually kissed him full on the mouth, all soft and careful. And then he was gone again.

"Could you open your mouth a little?" Lance asked.

Keith's head was either still stuck a few seconds in the past or Lance hadn't waited for a response. The second kiss was even weirder, what with Lance's tongue sort of swiping past Keith's lips, but not full on pushing through like he'd seen in movies. He was kind of glad for that. French kissing always looked so uncomfortable.

"Not bad," Lance said the next time he pulled away. A half smile sort of snuck up on his face, and only later would Keith realize it was a sort of teasing expression. "You're a little stiff, but I don't think we'll have a problem convincing your mom we're in love." He ended with the last word in a sugar-coated, sing-song tone and a waggle of his eyebrows.

Once they'd stretched out a bit, stocked up on drinks and snacks, they were back on the road. Keith's mind, which had been left behind, came racing back when they got stuck behind an SUV with a trailer hitched to the back of it. He slowed down a bit, checked the lines and the other lane, switched, and then drove his foot into the gas pedal.

"Holy Tostitos, Batman," Lance hissed, holding onto the handle above the door.

Keith ignored him in favor of getting back in their lane, before the truck heading their way made it to the same spot they were.

"Could you slow down? Maybe?"

"Why?"

"Because I want to live? I've been wondering, do you always drive this fast?" Lance asked. He hadn't loosened his grip on the handle.

"It's not that fast."

"Dude, you are going like, ten or twenty over the speed limit, I am sure of it," Lance insisted.

The rolling of his eyes did not go unnoticed.

"Don't be blaming me if you get pulled over by a cop. Or we hit a patch of ice and go spiraling off road, only to hit a tree and die. Won't be my fault when you get blisters on your ass for landing yourself in hell because you killed lil' ol' me and--"

"Oh my god, shut up!" Keith shouted and added pressure to the brake pedal. "We aren't going to die! My driving skills are great -- better than great! Haven't had an accident in my entire driving career."

"Don't go jinxing yourself now."

"I am going to throw you out the car."

"Going 90 miles an hour?"

"Yes," Keith said and traded a grin with his obnoxious fake boyfriend.

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Hope you liked it!! <3 <3

#klance #keith kogane #lance mcclain #voltron #vld #fake bf trope #fakest of fake bfs #super cliche plot #but I LOVE WRITING IT SO OH WELL #i wanted to try writing a slow burn #but it is not going quite as slowly as i had planned #so #it'll probably be done in 6-7 chapters??#ANYWAYS I HOPE YOU LIKE IT #i put the ao3 link cause imo its easier to read

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juniperpublishers-imst · 5 years ago

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Caveability Assessment of a Hanging Overlying Massive Deccan Trap and its Effect on Underground - Juniper publishers

Journal of Insights in Mining Science & Technology

Abstract

Efficient and safe extraction of coal from underground mines require regular/smooth caving of the hanging overlying strata in goaf which is intended to fall. Sometimes presence of extremely difficult to cave massive strata (EDTCMS) having higher strength and thickness as immediate roof delays the natural caving and affect adversely the depillaring operation in underground mines. Such EDTCMS are found globally (India, China, United States, Czech Republic) with thickness varying to hundreds of meters characterised as igneous/sedimentary formations. It is found to be lying either just immediately above or after a certain parting from the coal seam. The latter is found more frequent to the former in coalfields of the world including India. Bulking factor plays a major role in filling the void by the falling of the partition between coal seam and EDTCMS. When a large overhang of EDTCMS is created in the void then their sudden breakage may generate issues like dynamic weighting, floor heaving, pillar spalling, coal bump/rock burst, goaf encroachment/pillar failure and air blast in and around the face. Dynamic weighting by a dolerite sill in the roof destroyed the integrity of almost half of the chock shields in less than 4 second at Churcha West Colliery, India. Various techniques have been adopted worldwide to deal with the issues due to EDTCMS like their pre-fracturing, induced blasting, leaving wider barrier pillars at the face, back filling and injection of grouting material into the mining-induced overburden. This paper presents a case study discussing issues of spontaneous heating and pre-mature collapse of pillars due to EDTCMS at Mathani Underground Mine.

Keywords : EDTCMS; Depillaring; Immediate Roof; Caving; Dynamic Weighting

Introduction

Usually, it is found that the immediate roof in underground coal mines mostly consists of shale, clay, sandstone and their intercalation with thickness varying from 0.1-10m. When coal is extracted below such roof then it keeps hanging in the void space (goaf) created. Such strata caves easily and regularly without creating high induced stresses after a certain exposure as experienced in Pinoura underground mine in India [1]. Initially, the hanging roof in goaf is supported from all the sides and acts as a strong beam, inhibits caving. After a certain exposure, the strong beam fails/caves in goaf to become cantilever which keeps caving regularly. It is the story when working under easily to moderate caveable strata where roof fall takes place regularly on certain exposure of roof span. Sometimes extremely difficult to cave massive strata (EDTCMS) of sedimentary/igneous rock type is present in the roof having higher strength and thickness in hundreds of metres, delays the natural caving and affect adversely the depillaring operation in underground mines. Such strata keep extending their span without caving in the void space created and leads to a major accident in the mine. It is found to be lying either just immediately above or after a certain parting from the coal seam (Figure 1). EDTCMS located after a parting from coal seam have lesser chances to affect towards the working due to the filling of the void by caving of the partition (Figure 1a). When EDTCMS is found just immediate of the coal seam then it keeps hanging over a large span in the void without any failure and transfers load towards the working resulting into issues of coal bump/rock burst (Figure 1b). Mostly it is found after a parting from the coal seam. When a large overhang of EDTCMS is created in the void then their sudden breakage may generate issues like dynamic weighting, floor heaving, pillar spalling, coal bump/rock burst, goaf encroachment/pillar failure and air blast in and around the face. There is an incident of dynamic weighting by a dolerite sill in the roof which destroyed the integrity of almost half of the longwall chock shields supports in less than 4 second at Churcha West Colliery, India (Table 1). Another incident of water inrush occurred followed by a coal and gas outburst during the drivages of the gate roads at the Haizi Coal Mine in China (Table 1). Load of the EDTCMS is mostly shared by the coal pillars and the parting between it and the coal seam keeps falling regularly. EDTCMS starts building high abutment load towards the working causing the premature collapse of coal pillars. Goodrich et al. [2] has studied the load transfer distance by EDTCMS in United States coal mines. Less studies are available on measurement of mining induced stress under EDTCMS in Indian coal mines.

The parting between the coal seam and EDTCMS caves in the void by the stress-induced fracturing or goaf blasting technique or fall under gravity. Further, when the hanging rock fragments’ separate from the overlying rock mass, there are likely chances of rotating these irregular sized and shaped fragments’ in the void space. As a result of falling on to the ground there is possibility of reduction in size of rock fragments. It results into an increase in volume as broken rock fragments do not lock with each other perfectly causing inefficient packing due to air gaps between them. This increase in volume of rock mass to the actual volume is called bulking factor (BF). Height of caved zone is mostly dependent upon the BF of overlying strata during depillaring of coal pillars. Bulking of rock by blasting is completely different phenomenon from the natural caving of rock. As per previous studies, BF of different rock mass is found to be ranging between 1.05 and 1.84. Thus, if the parting is enough to fill the void created by coal extraction then there is least effect of EDTCMS towards the working. Sometimes, bulking of the parting is not enough or thickness parting is not enough to fill the void after their caving in the goaf. In this case, EDTCMS keeps hanging over a large span creating several issues towards the working. Various techniques have been adopted worldwide to deal with issues due to EDTCMS like their pre-fracturing by high pressure water injection [3] or induced blasting [4] (Figure 2), leaving wider barrier pillars at the face, back filling and injection of grouting material into the mining-induced overburden [5] (Figure 2).

Mathani underground mine lies in the Thesgora block ‘A’ between the latitude 78054’37” to 78057’36” and longitudes 22013’17” to 22014’55”, located at Chhindwara district of Madhya Pradesh, India. This underground mine was explored during 1992 and mining activity started in 1994. It is situated about 27 km east of Parasia town in the Pench valley. The area exhibits a rugged terrain comprising hills and valleys. Seasonal nallah runs in the block and drains to either Gunar or Pench river. Mathani village has a population around 350 persons, which lies in the middle of the Mathani underground mine’s property in the northern boundary. The seam of Mathani underground mine has Degree II gassiness level with an incubation period of 3 months. A total of 11 coal seams/section viz seam/sections-IA, I(B+C), IIA, II/IIB, IIIB, IVA, VA, VB1, VB2, VB and VC in descending or der at different depths of cover are present in Mathani underground mine. Among these coal seams only three coal seams i.e. I(B+C), IIIB and VA are workable, and rest are unworkable due to their poor thickness and less span. Seam VA is present throughout the property and found in almost every borehole, whereas seams I(B+C) and IIIB are absent or having unmineable thickness in few boreholes. Depth of cover for seam I(B+C) is found to be varying between 60-168m and seam IIIB is between 69-162m. The parting between seam I(B+C) and IIIB is less than 9m (varying between 2-7m) and is being worked contiguously with superimposition (Figure 3). The parting between the Deccan Trap and Seam I(B+C) is varying from 2-60m and thickness of the Deccan Trap is varying from 40-150m as per the various available boreholes data. Seams I(B+C) and IIIB are contiguously developed into various panels with pillar size 21.30m x 25.50m and gallery size 4.2m x 3.0m. Depillaring with caving approach by conventional drilling and blasting method is being carried out in contiguous section at the Mathani underground mine, leaving a rib of 2.3m width in both the seams which is further reduced judiciously during retreat. Around 9 panels (1A, 1B, 1C, 1G, 1H, 1I, 1J, 1K, 1L) of seam I(B+C) (Figure 4) and 9 panels (3A, 3B, 3C, 3G, 3H, 3I, 3J, 3K, 3L) of seam IIIB (Figure 5) are depillared successfully. Deccan Trap (basaltic sill) having thickness varying between 40-150m (Figure 6), lying as overhanging roof in the caved goaves of seam I(B+C). Problem of goaf encroachment causing overriding of pillars, faced while caving of Panel 1M of seam I(B+C) which further caused pre-mature closure of this panel and subsequently 3M Panel of seam IIIB also. Further, it kept affecting the barrier pillars by inducing fracture from corners and subsequently working pillars in the Panel 1N. Barrier and working pillars are under continuous deformation (from the dip most side) due to the incidences happened in previous Panel 1M. It has encroached up to two rows of barrier pillars in Panel 1N creating issue of reserve loss and strata control. It is guesstimated that the Deccan Trap is almost unbreakable to cave for the formed void and the mining induced stress created by the depillaring of previous 9 panels of the seam I(B+C) is causing the instability issues of natural supports during the working in Panel 1N. Accordingly, it is planned to study the caveability of hanging overlying massive Deccan Trap in the goaf of seam I(B+C) and its effect at this mine. It is found during the working in seam I(B+C) is difficult due to the mining induced disturbance in the Deccan Trap. It is diluting the strength of the working and barrier pillars and encroaching and affecting the working area. This encountered problem of the mine forced to leave two rows of barrier pillars between the depillared Panel 1M and working Panel 1N. Further, it is also found that the working in Panel 3M of seam III B is becoming difficult due to failure of the parting between seam I(B+C) and IIIB but the pillars are still intact. Geo-mining details and required information are collected for assessment of caveability of hanging overlying massive Deccan trap in the inbye goaves and its effect at Mathani underground mine. Details of the studied problem is mentioned in this report.

The pillars are found to be spalling up to 1-1.5m from all the sides and it is more visible in the dip most side, when compared to that of rise side in the pillar. Further, it is increasing gradually, causing the gallery width to increase from 4.2m to more than 6m. The parting between Deccan Trap of thickness 40-150m and Coal Seam I(B+C) is varying between 2-60m. However, the thickness of this parting at the present working is around 10m only and the height of the working is 3m. This parting is mostly consisting of arenaceous (sandy) clay and coarse to medium grain sandstone with less bulking factor (BF). There is no evidence of goaf packing by caving of fragmented overlying strata. Usually, BF for coal measure formation is 1.1. Field investigation noticed in Panel 1N of coal seam I(B+C) that the roof deterioration is in V-shape form along dip-rise galleries (Figure 7) and is found to be a simple manifestation of instability in the gallery. Extraction of coal by conventional drilling and blasting further deteriorates and dilutes the competency of roof and pillar. There is no observation of any mining induced movement in the Deccan Trap but overriding of pillar and goaf encroachment has been experienced in Panel 1M after extraction of 5 pillars in a panel of 12 pillars. It is guesstimated that the observed dilution of barrier pillar strength in Panel 1N has happened due to the load transferred by the Trap. Further the same incident continued and caused to leave two rows of barrier pillars between Panel 1M and 1N. Local fall regularly occurred up to a height of 3 m after a goaf exposure varying from 77-87m2 and the goaf is found to be filled partially. Panel 1M started on 18-06-2018 and the working discontinued due to pillar crushing and then panel was sealed on 23-08-2018 (Figure 8). Only local fall was observed during working in this panel. No monitoring is being carried out by any instrument, which makes the study incomplete for understanding of the strata mechanics. Seam IIIB is a low height seam at a parting varying from 2-7m between seam I(B+C) and IIIB. It is being worked in contiguous section. This parting mostly contains coal seam II with alternating bands of shale sandstone. This parting is not stable due to its poor competency, mainly due to poor thickness of laminated formation (shaly sandstone and coal seam II). During the mine visit it is found that the roof (parting between the two seams) of seam IIIB is getting detached even around the intact pillar. The working in Panel 3M (Figure 8) is abandoned due to the encountered problems in Panel 1M of seam I(B+C) The geology of the area is based on the geological report on exploration for coal in Thesgora Block ‘A’ P.K. Valley Coalfield, District Chhindwara Madhya Pradesh prepared by MECL in January 1989. The entire area is covered by basalt, Jabalpur moturs and barakars are concealed under the cover of basalt flows. The area exhibits a rugged terrain comprising many hills and valleys. The maximum and minimum elevation being 791.22 m to 727.61m respectively above MSL. The general geological succession has been proved by sub-surface details as obtained by boreholes drilled from time to time. Based on borehole data, the lithological formations present in the area under consideration have been summarised in Table 2. The exploration in Thesgora Block ‘A’ has confirmed existence of a total of 11 coal seams/ sections viz seam/sections-IA, I(B+C), IIA, II/IIB, IIIB, IVA, VA, VB1, VB2, VB and VC in descending order. The general sequence, thickness of coal seams and parting ranges are given in Table 3.

Description of coal seams

Seam I(B+C) is the youngest seam in the area. The depth range of the floor of this seam varies between 60.45-139.91m with thickness varying between 5.17-7.31m (most prevalent range being 6-7 m). Immediate roof contains dominantly shale and immediate floor contains sandstone mostly. Dirt bands varying from 0-0.3m is present in this coal seam. Seam II/IIB underlies seam I(B+C), at a parting range between 0.47-2.47m consisting mostly of sandstone with shale band. The parting of seam II/II B with underlying seam III B varies from 1.20-3.71m.

The depth of cover varies between 66.04-142.79m with seam thickness ranging between 1.50-3.50m (mostly 1.50-2.50 prevalent). Immediate roof and floor contain shale mostly. This seam is generally devoid of any dirt bands. Seam IIIB underlies seam I (B+C) at a parting ranging between 5-7m consisting mostly of shale with sandstone bands and coal seam-II/IIB. The parting of seam IIIB with overlying seam II/IIB is varying from 1.20-3.71m, which is dominantly consists of shale. Its depth range varies between 67.86-147.4m with seam thickness variation 1.74-2.28m (most prevalent 1.5-2.0m). Immediate roof and floor contain shale and sandstone respectively. No dirt band is present in this coal seam. Seam VA underlies seam IIIB at a parting ranging between 10-20 m generally. The parting in the considered area varies between 13-16m and is mostly consist of sandstone with thin shale bands. This coal seam lies below depth of cover ranging between 83.02-164.81 m with seam thickness varying from 2.37-6.82 m (most prevalent is 4-6 m). Immediate roof and floor of this seam are sandstone and shale respectively. No dirt band is present in this coal seam. From the above Table, it can be seen that out of these 11 coal seams/sections only four I(B+C), II/IIB, IIIB and VA attain workable thickness.

Method of Working

Based on geo-mining and financial considerations, the mine management has decided that all seams would be extracted by Bord and Pillar method, seam I (B+C) and III B would be worked contiguously and seam II is being left out due to low inter-seam parting. Parting between floor of seam VA and IIIB is about 16m and that of between seam IIIB and I(B+C) is about 8 m. This brings out a drift length of 60m up to III B and 90 m up to seam I(B+C). Upper seam I(B+C) is approached by two intakes drifts and two return drifts from the main dips via III B seam. Main dips are driven in seam V A from the surface. The working panels in both the seams are opened from these drifts and dips. Seam I(B+C) and IIIB are being worked contiguously as the parting between these two seams is less than 9m and thus the workings are developed as per Coal Mines Regulation 104 (CMR 1957) by prior permission from DGMS. Pillars in upper seam I(B+C) are coinciding vertically with the pillars of lower seam III B. Size of the pillars and galleries in these panels are developed as per Regulation 99 of CMR 1957. The length of a panel is kept around 600-800m, but the panel is divided into different sub-panels of around 100 m length and 75 m width based on the estimated production and incubation period. Seam III B is around 2.0m (a low height) thickness and is being extracted by B&P method. Seam I(B+C) is having thickness from 5-7m with relatively inferior coal in roof. The method of extraction adopted here in this seam is to split the pillar in two halves by a level split of 4.8m x 3.0m dimension. Dip slice of 3m height and 4.5m width is to be driven leaving a rib of 1.8m against the goaf. Coal in roof is blasted by drilling of holes on retreat with an interval of 1.2-1.5m spacing similar like Blasting Gallery method. Rib is also being reduced judiciously on retreat along with the roof coal.

Rock Mass Rating

As per the available documents with the mine management, the RMR of immediate roof for seam VA is 30.60 belongs to poor roof category and seam II is 31.5 belongs to poor roof category. RMR of immediate roof for seam I(B+C) is 37.26 belongs to poor roof category and seam IIIB is 34.02 belongs to poor roof category. The compressive strength of shaly sandstone present in immediate roof of seam I(B+C) is 12.00 MPa. The compressive strength of moist coarse-grained sandstone present in immediate roof of seam VA is 0.80 MPa. The compressive strength of shaly sandstone present in immediate roof of seam II is 2.70 MPa. The compressive strength of shaly sandstone present in immediate roof of seam II is 7.22 MPa.

Support System

In addition to the basic purpose of the support system, it is supposed to give sufficient free space for the movement of machineries. Accordingly, all development galleries are being supported by roof bolts with or without roof stitching. Few hydraulic props of 10t capacity are provided to cater the urgent need supports at the faces. All the galleries lying within 3 pillars from the pillar under extraction are kept supported by 1.5m long full column grouted roof bolts at spacing of 1.0 m between the bolts in a row and 1.0 m between the rows of bolts and strengthened with W-straps at a matrix 1.0m x 1.0m. The junction is supported by 25 % extra bolting along with four numbers of W-straps. Also, one wooden/steel chock at a suitable location without hindering in movement of LHDs is provided at the junction. To prevent side spalling the sides of 3 pillars from pillar under extraction including split and slices are supported with fixing of bolts of 1.5m length in the side wall at a grid spacing of 0.75m x 2.0m in three horizons all along. Whole pillar is strengthened with rope stitching and kept tightened with wooden laggings from the side. All the split and slice galleries are kept supported by 1.5m long full column grouted roof bolts strengthened with W-strap at a matrix 1.0m x 1.0m. In addition to the above supports, wooden chock or steel chocks topped with at least 30% wooden slippers are set alongside of the rib side at an interval of 2.4 m and one rows of props are provided in between the chocks in each slice. Ledges (V-shaped deformation) formed are supported by three bolts of 1.5m length with W-straps.

Caveability Index

Assessment of caveability of overlying strata is vital for the method of extraction and design of underground structures during pillar extraction. The caving nature of overlying roof strata during depillaring of a coal seam depends on their thickness and the uniaxial compressive strength. Previous experiences of working in underground mines have revealed that a thick, strong and massive stratum caves after a large suspension inside the goaf and develops large mining induced stress transfer distance towards the working. Whereas, a weak/laminated roof stratum caves regularly and smoothly without their much overhang.

Based on different field studies, the caving characteristics of overlying strata are quantified in terms of Caveability Index (I) [6], which is defined as:

0.5 (1) 5 nlT I σ =

Where,  = Uniaxial compressive strength in kg/cm2, l = Average length of core in cm and T = Thickness of the strong bed in m and the factor n has a value of 1.2 in the case of uniformly massive rocks with a weighted average of RQD of 80% and above. In all other cases n = 1. This value of I is to be calculated for roof thickness equal to 10 times of the height of extraction and the corresponding values are matched with the indices provided in Table 4 to decide the nature of caveability of a stratum. Generally, fresh core samples of the roof strata are procured and subjected to laboratory testing for an assessment of I to understand the caving nature of overlying strata. However, an assessment of I at different depillaring panels of mine is undertaken to judge the caveability of roof on the basis of the data provided by the mine management. Provided values of the physico-mechanical properties of overlying formations indicate that the strata between seam I(B+C) and Deccan Trap is easily caveable. However, Deccan Trap is difficult to cave due to their inherent strength and thickness.

Caveability of massive deccan trap and bulking factor

Based on the above-mentioned formulation, the Caveability of massive Deccan Trap comes to be around 5400, which is under category III (Roof caveable with difficulty). Further, looking at the thickness of the Trap, a considerable section of the overlying strata is found to be caveable with difficulty, which makes the final extraction under the shadow of dynamic loading too. In fact, if sufficient dimension of the void is provided to break the Trap under the condition then there is a strong possibility of dynamic loading, otherwise the pillar extraction in the seam going to constantly encounter excessive loading and an impending threat of global instability. The caveability of roof i.e. parting between seam I(B+C) and Deccan Trap comes to be around 1800 falls under category I (Easily caveable roof). Usually, bulking factor for Indian coal measure formations are taken around 1.1. The average thickness of coal seam extracted during depillaring is 6m including the extraction at the time of retreat in slices. The parting between seam I(B+C) and Deccan Trap varies between 2-60m. Generally, the thickness of parting between the coal seam and the Trap over the present working is estimated to around 10m only. However, as per the bulking factor estimation, the upper limit of the parting thickness is not away from the influence zone. Thus, it can be said that there is an effect of the Deccan Trap during depillaring with caving on the working for the existing parting thickness between seam I(B+C) and Trap. Such a geo-mining condition can be dealt by effective management of the Trap. This can be achieved either through its caving or through adoption of narrow panel extraction with a good design of the natural support. It is important to note here that the indirect increase in height of the pillars (especially pillar at the goaf edge and barrier pillar) during retreat for full height working is also a point to be considered during the design [7].

Effect of Deccan Trap on Mathani Underground Mine

Deccan Trap is a major issue in this mine due to its inherent strength and thickness and remains overhanging inside the goaf after caving of the immediate roof of seam I(B+C). The observed caving does not fill the entire cavity generated due to extraction of the thick seam under the massive Deccan Trap. The overhang of Trap is generating considerable potential energy, which in turn is causing excessive stress over the natural supports like barrier pillars. As the trap is still intact over different voids of the previous depillaring panels, the ongoing system of depillaring at this mine will keep facing the problem of pillar instability. The approach to overcome such situation can be implemented through design of squat barrier pillars for the heightened goaf and induced caving of the overhang Trap inside the goaf through long hole drilling and blasting also called destress blasting. As the coal seams are extensively developed, the scope of design of pillars is limited and the requirement of the squat pillars can be achieved through packing/filling some of the selected galleries by incombustible material like sand. A proper design of manner and dimension of extraction along with an increase in the efficacy of the barrier pillars may prove to be an immediate solution for the mine. Experienced local instability of the parting requires to be dealt with appropriate design of support system as the quality of the inter-burden strata is poor. Around 6m thick coal seam has been extracted (full thickness) in the previous 9 panels of the seams, which has changed the nature of barrier pillars from squat to slender (reduced width to height ratio). In Panel 1N, the parting between seam I(B+C) and Deccan Trap comes to be around 10m, and thickness of Trap is around 90 m. Such a less parting can play major role in creating dangerous condition of overhanging Deccan Trap causing pillars to fail (due to abutment load) and encroachment of goaf. Overriding of pillar and goaf encroachment has been experienced in Panel 1M after extraction of 5 pillars among 12. Further the same incident is repeated with two rows of barrier pillars of Panel 1N. Local fall occurred regularly up to a height of 3 m after a goaf exposure varying from 77-87 m2 and the goaf is found to be filled partially. Panel 1M started on 18-06-2018 and working discontinued due to pillar crushing then panel sealed on 23-08-2018, where the massive overlying Trap has played significant role [8].

Conclusion

Although underground coal mining requires site specific design from very beginning, the encountered geo-technical issues in depillaring at the Mathani underground mine is, mainly, twofold:

(i) indirect increase in extraction height (heightened goaf) and

(ii) difficulties involved in destressing the mined-out area as the existing Deccan Trap keeps overhanging inside the goaf.

As the coal seams are extensively developed so the design of natural support has slim scope for any major improvement in their efficacy. Deccan Trap is a massive formation whose thickness varies from 40-150 m, lying in the roof of seam I(B+C) in the mine. The parting between seam I(B+C) and Deccan Trap is varying from place to place. In Panel 1N, the parting between seam I(B+C) and Deccan Trap comes to be around 10 m and thickness of Trap is around 90 m. Such a less parting plays major role in creating dangerous condition of overhang, which in turn is causing pillars to fail and encroachment of goaf inside working, Further, it is found that partial extraction (2-3 m of coal seam thickness) to control the height of caving would help in avoiding any movement to be induced in Trap when parting between seam I(B+C) and Deccan Trap is less than 60 m. However, in this situation, the excessive loading of the pillar will exist. The other approach would be destressing of the worked-out area by breaking the Trap for caving. This can be achieved by a suitably designed larger dimension of the void and adopting induced fracturing through long hole drilling and blasting. The blasting can be done from the existing underground openings but requires special equipment and effort to execute it. The attempt of caving/destressing should be practiced in presence of the competent natural supports, especially the barrier pillars. The competency of the existing natural support can be achieved through introducing a favourable tri-axial confinement condition as the discrete side support of pillars may not be effective. Reduction in the height of the final extraction (i.e. depillaring) is also an option to overcome the strata control issues of the depillaring.

Previously, Panel 1M of seam I(B+C) has been abandoned after extraction of 50% coal (from 12 pillars) due to overriding of pillar by goaf encroachment. Parting displacement in roof of seam IIIB can be restricted by proper installation of supports for which goal-post type support and/or W-straps with roof stitching may prove to be a better option. Further understanding about the goaf encroachment could be established through field instrumentation and strata monitoring. When the mine management planned to extract coal from Panel 1N of the same seam, they experienced failure of barrier pillars, which could have been avoided through the presence of a squat barrier pillars. It caused to leave one more row of barrier pillars in Panel 1N. Any induced movement in Deccan Trap may create apprehensive condition in the working leading to loss of men, coal and machinery but it is not confirmed yet whether movement in Deccan Trap has been considerably been initiated or not. It is required to install geo-technical instruments like stress meters, auto warning tell-tale, multi-point extensometers, load cells, instrumented roof bolts in the workings at selected locations to avoid any dangerous situation due to movement of the Deccan Trap. Further, a strata control team to look after the recordings of the installed instrument to give warning about any dangerous and risky condition in the mine would help in strata management. Depillaring with stowing is another option for the site but it will affect productivity along with associated operational and financial implications.

Acknowledgment

The authors express their thankfulness to the Director of CSIR-CIMFR for permission to publish this paper. The views expressed in the paper are those of the authors, and not necessarily of the institutes to which they belong. The co-operation provided by the management of Mathani Underground Coal Mine, Western Coalfields Limited (a subsidiary of Coal India Limited), Madhya Pradesh is thankfully acknowledged.

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