The machine hummed, the drill bit slowly pressing into the soil, mud and debris churning out of the pit and landing at Chen Hao's feet. He gripped the handles of "Groundhog No. 1" tightly, leaning forward as if pushing a broken-down cart stuck in the mud. Susan stood beside him, holding a flashlight; the beam shone into the newly dug hole, revealing that the drill bit was still turning, though much slower than before.
“This soil is getting harder and harder.” Karl squatted down and reached out to touch the pit wall. “It was loose a moment ago, but now I can’t even squeeze it.”
Nana stood at the back, her eyelight flashing as she transmitted data to the internal system. "Current tunneling depth is 1.8 meters. Soil density is continuously increasing. It is recommended to reduce the drilling speed."
"Can we go any further?" Chen Hao gasped for breath, his face covered in mud, his lips twitching as he spoke.
“Yes, but the risk increases,” Nana said. “The equipment’s temperature control has reached 76 degrees Celsius. It will automatically shut off the power if the temperature exceeds the safety threshold.”
"It's okay, I feel fine." Chen Hao didn't let go, but instead put more effort into it. "It's just a matter of those two shovelfuls of soil left. Let's finish it in one go so we don't have to come back later."
The moment he finished speaking, the drill bit suddenly stopped, and the entire machine jolted violently, as if it had hit a metal plate. Chen Hao's arm went numb from the recoil, and he almost threw the machine away. He quickly released the switch, and the machine immediately stopped, with only the power cord still slightly warm.
"Is it stuck?" Susan leaned closer to take a look.
“It’s not a card.” Karl reached out and tapped the bottom of the pit. “It hit a rock.”
Chen Hao bent down and brushed away the topsoil, revealing a dark gray rock surface. The surface was smooth, and there were no visible cracks along the edges. He rubbed it with his finger, but even his fingernail couldn't leave a mark.
"Where did this thing come from?" he asked Nana, looking up. "Isn't this all sand and soil around here?"
Nana stepped forward, pointed the optical lens at the rock, and reported the result a few seconds later: "Highly silicified sandstone, formed in a high-pressure geological environment, with a hardness close to that of granite. Such rock layers usually do not appear in isolation."
"Does that mean—there's more below?"
"Very likely."
Chen Hao stared at the rock, then looked at "Groundhog No. 1" and noticed that the tip of the drill bit was a bit blackened, as if it had been baked by high temperatures. He reached out and touched it, and felt a stinging pain in his fingertips.
"Burned?"
“Local overheating.” Nana took the machine to inspect it. “The vibration frequency resonates with the rock mass, causing a concentrated release of energy. If we continue to operate, the drill bit will break within three to five impacts.”
"So it's unusable?" Susan frowned.
“It’s not completely unusable,” Nana said, “but with this kind of rock formation, the efficiency will drop to less than 10 centimeters per hour, and the equipment’s lifespan will be shortened to less than 15 minutes.”
"Then we might as well dig with our hands." Chen Hao sat down on the ground and wiped his face. "I should have known better than to brag that we could break through tonight."
Carl tapped around the edge of the pit with an iron rod, producing a series of muffled sounds. He tried several spots, finally stopping three steps to the left, where he crouched down and dug away a thin layer of soil.
“It’s hard here too,” he said. “Not just this one spot, but the whole area.”
"Connected?" Chen Hao crawled over to take a look.
"Hmm. It's at least half a meter deep, and you can't see the boundary when it extends horizontally."
The air fell silent. Susan removed the drill bit, examined it against the light, and noticed a tiny crack on the cutting edge. She didn't speak, only sighed softly.
"How about... we stop for a day?" she said. "We'll figure out a solution later."
"Stop?" Chen Hao looked up at her. "We just installed lights on the wall and the alarm system isn't working yet. If we don't dig the tunnel quickly, what if someone sneaks in one night? We won't even have a place to hide."
“But if we keep pushing like this, we’ll only break the tools,” Carl said. “In the end, we won’t even be able to put together a single piece of scrap metal.”
"I know." Chen Hao stood up, brushing the mud off his pants. "I'm not saying we have to dig through tonight. I'm saying we can't give up just because of one rock. We went through so much trouble to get this broken machine up; we can't let it break down on the first day, can we?"
Nana looked at him, her eyes shifting from blue to green. "You have a concrete plan?"
“No,” Chen Hao said honestly. “But I remember you said that there used to be a small geological exploration station nearby, and maybe some rock-breaking tools were left behind.”
“The site of the exploration station has been confirmed in the seventeenth search,” Nana said. “No usable equipment remains.”
“Then let’s look at it again,” Chen Hao said. “Or let’s try a different approach. Can anyone think of another way? Like, something around it?”
“We could try digging at an angle,” Nana analyzed. “But the thickness of the rock strata is unknown. If it exceeds one meter, turning around won’t make much difference.”
"How about an explosion?" Susan suddenly asked. "Is it possible to set up a small explosion?"
“There’s no gunpowder,” Karl shook his head. “There’s nothing to use as a fuse.”
"What if the battery short-circuited and sparked?" she pressed.
“The voltage is too low to ignite flammable materials,” Nana replied. “And the operation is extremely risky and could trigger a chain reaction.”
"So we just have to tough it out?" Chen Hao squatted back down by the pit and stared at the rock for a long time.
The streetlights in the distance were still on, their light casting shadows on the muddy ground and making several figures appear. The wind blew through the cracks in the wall, causing the power lines to sway gently.
“I remember when we were laying foundations on construction sites, we used pneumatic drills to chisel away hard rocks,” Carl said. “Those things rely on compressed air to impact the rock, which is much more powerful than a vibratory drill.”
“The problem is we don’t have an air compressor,” Chen Hao said. “We don’t even have an air pump.”
“But the principle is the same.” Carl pointed to “Groundhog No. 1”. “It’s driven by a motor to vibrate. If we can change the impact method to intermittent hammering, we might be able to break through the surface.”
"You mean... change it to a hammer?" Susan asked.
"Pretty much." Karl nodded. "You don't need much strength. As long as the frequency is fast enough, you can break the stone by tapping it repeatedly."
Nana paused for a few seconds, then brought up the internal model. "If the existing gear set is reconstructed into an eccentric hammer structure, combined with spring buffer, it can simulate a simple impact action. However, the drive shaft needs to be replaced, and the outer shell needs to be reinforced to withstand the recoil force."
"Do you have the materials?" Chen Hao asked.
"There is still a section of steel pipe left, which can be used as a new axle. The springs can be obtained from the suspension system of scrapped vehicles."
"Then what are we waiting for?" Chen Hao slapped his thigh. "Let's go rummage through the junkyard tomorrow!"
“The modification will take time,” Nana cautioned, “and there’s no guarantee of success.”
“I know,” Chen Hao grinned, “but it’s better than just sitting here doing nothing. Besides, we’ve already pieced together ‘Gopher No. 1’ from this pile of junk, surely we can’t even manage a hammer?”
Susan looked down at the drill bit fragments in her hand and suddenly said, "When I was little, I saw my dad repairing tractors. He used a chisel and a sledgehammer to smash the carbon buildup in the engine. He said back then that even the hardest thing will eventually crack if you keep hitting it."
“That sounds plausible.” Carl stood up. “I’ll go take apart the car tomorrow and see if I can find a suitable hammer.”
"Let me draw a sketch." Chen Hao took out his notebook, tore off a page, laid it on the ground, and started doodling with a charcoal pencil. "We don't need to make it too fancy, just something that can be swung around."
Nana squatted down beside him, her eyelight casting a soft glow onto the paper. "I suggest adding anti-slip texture to the grip and adding weights to the head to improve striking efficiency."
"You're quite particular." Chen Hao looked up and smiled. "Alright, I'll do whatever you say."
They gathered around the dirty piece of paper and started discussing it, their voices gradually growing louder. Susan also joined in, pointing out a few spots where the welds were prone to cracking. Carl suggested adding a shoulder rest to the rear to save effort.
As Chen Hao revised the name, he muttered to himself, "What should we call it? 'Groundhog No. 2' is too low-class, and 'Rock Breaker' is too childish... How about 'Iron-Headed Brothers'?"
“Naming has a lower priority than functionality,” Nana said.
"Can't you be a little more cooperative?" Chen Hao pouted. "At least give me some creative freedom."
“You can call it whatever you want,” Susan said with a smile. “It won’t answer anyway.”
A night breeze blew in, lifting a corner of the paper. Chen Hao reached out and pressed it down, the pen tip drawing a long line on the paper. He didn't erase it, but instead drew the outline of a hammerhead along the line.
“That’s settled then,” he said. “Whatever we call it, we have to start work tomorrow.”
Nana withdrew the projector, and the eyelight returned to normal. "The equipment has cooled down. Shall we proceed with the final shallow test?"
"Test it." Chen Hao reconnected the power to "Groundhog No. 1". "Even if it only digs ten centimeters more, it's still progress."
He pressed the switch, and the machine started again, but this time he only allowed the drill bit to lightly touch the rock surface. A vibration sounded, and mud chips flew a few times before stopping. The drill bit ground a white mark on the rock before jamming completely.
Chen Hao turned off the power, picked up the machine, and glanced at the thermometer: 83 degrees Celsius.
"It's cold," he said.
Karl walked over and tapped the rock face three times with his iron rod. The sound was dull, like striking thick sheet metal.
“This rock is quite large,” he said.
Chen Hao squatted down, placed his palm on the rock surface, and pushed hard. It didn't budge.
He didn't say anything, but slowly stood up, wrapped the power cord around his shoulder, and hung it on his shoulder.
"See you tomorrow," he said.
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