189: Chapter 189 The Last Relay

unit 3 smoothly entered the maintenance tunnel along the route forged by unit 1 in the darkness.

The light supply pod on its back was not completely sealed so that rescue personnel could access it at any time.

Four bottles of drinking water, a two-way communication terminal with lighting, waterproof-wrapped hemostatic materials, and six thermal blankets were individually secured in slot cards with fluorescent markings.

Fire Rescue Group 1 followed behind the machine.

The six rescue personnel formed a single file line, slowly advancing close to the relatively intact wall.

They had already rehearsed the entire route in their minds beforehand using the high-precision 3D map transmitted back by unit 1.

At the six-hundred-and-twentieth meter mark, they needed to duck to avoid the hanging metal lamp holder.

At the nine-hundred-and-thirtieth meter mark, they needed to detach external equipment and crawl underneath the deformed ventilation pipe.

The main tunnel near the maintenance vehicle was completely blocked, and they had to enter the narrow maintenance tunnel from the right maintenance door.

These dangerous locations were individually marked on everyone's portable terminal.

Within the temporary command area, communication with the drainage pump house remained clear.

The four maintenance personnel behind the door had stopped their exhausting knocking.

Since the two-way voice terminal had not yet been delivered, unit 1 could only converse with them using an external speaker through the gap less than thirty centimeters wide below the door panel.

"Where is the water level now?" Chen Yan asked into the microphone.

The man behind the door panted, his voice carrying a hypothermic tremor: "A little bit above the ankles, it's not rising very fast."

"Can the person who is pinned still feel their feet?"

"I can feel the pain."

"Do not force your leg out right now."

Medical team personnel quickly took over the communication link, asking about injuries one by one across the gap.

The situation was rapidly compiled.

One maintenance worker's left leg was pinned by a fallen equipment bracket, and the fracture status was unknown.

Another person suffered a forehead injury and had already stopped the bleeding themselves using torn clothing.

The remaining two had minor abrasions to varying degrees.

No excessive levels of harmful gases had been detected inside the pump house yet, but the ambient temperature was plummeting rapidly, and everyone was completely drenched.

Chen Yan shifted his attention to the status bar of unit 4 at the edge of the screen.

There was still no news regarding the remaining three missing personnel.

After leaving the pump house area, two road inspection personnel had continued eastward along the maintenance tunnel.

The person they were looking for was a truck driver.

Starting from the pump house junction, the environmental map behind was completely pitch-black and blank.

"The fourth unit is ready to enter." Chen Yan looked at the head of the headquarters.

"The two relays carried by unit 2 have all been deployed. The last remote relay remains at the entrance as a backup." Chen Yan brought up the structural diagram, "According to the original design drawing, there is a second maintenance door two hundred meters east of the pump house. If the environment has not changed, placing the last relay there will allow the signal to cover up to around nineteen hundred meters."

The head of the headquarters frowned: "What about further ahead?"

"Further ahead, there are no physical relays."

"Can the machine still move?"

"It can move." Chen Yan paused slightly, his tone serious, "But real-time communication cannot be guaranteed."

"What if communication is lost midway?"

"According to the currently set mission rules, the machine will stop advancing and attempt to recover in place. If continuous communication loss exceeds the set time, it will automatically trigger the withdrawal procedure."

The geological personnel switched the latest round of monitoring data onto the main screen.

The overall displacement speed of the landslide body was decreasing, which was good news.

But another worrisome change had appeared inside the tunnel.

Between 1,300 meters and 1,700 meters, two sets of micro-vibration sensors installed above the ground surface continuously captured several low-frequency responses.

The source could not be accurately determined.

It might be huge loosened rock blocks continuing to fall, or it might be the tunnel lining structure redistributing the mountain's pressure.

"Personnel can enter the pump house now, but cannot continue eastward." The geological personnel drew a line with a red pen on the orange area of the screen, "There is no direct data transmitted back by any robots here. Before confirming the structural state, I do not recommend any rescue personnel crossing the pump house."

At 5:11 PM.

unit 4 entered the tunnel.

It did not carry a bulky supply pod.

Its back only retained a full set of search modules, a high-strength soft rope for short-distance towing, and a detachable two-way communication and lighting terminal with a camera.

To minimize mechanical noise interference, its foot servo speed was forcibly restricted to 70% of routine tasks.

Unit 5 still quietly parked at the entrance.

It was the only complete backup platform on-site that had not been put into use.

Xu Man stood beside the transport vehicle, re-inspecting the towing components of unit 5.

At this time, unit 3 arrived at the obstacle area at the nine-hundred-and-thirtieth meter mark.

It lowered its fuselage and squeezed through bit by bit underneath the deformed ventilation pipe.

Between the top of the supply pod and the sharp edge of the pipe, there was less than a three-centimeter gap left.

One minute later, it raised its fuselage again on the other side of the obstacle.

Meanwhile, Fire Rescue Group 1 following behind was forced to stop on the west side of the obstacle.

The oxygen cylinders and demolition equipment they carried could not pass underneath such a flat gap like the machine could.

Two team members immediately stepped forward to start securing temporary hydraulic supports, while the remaining personnel started small cutting equipment, sending sparks flying as they attempted to dismantle one end of the ventilation pipe.

This was a place where machines could easily pass, but flesh and blood could not yet pass.

unit 3 did not wait, instead continuing forward according to instructions.

At 5:19 PM.

unit 3 arrived at the drainage pump house.

unit 1, which had been guarding outside the door all along, actively made way to the side.

unit 3 rotated its chassis, and the supply pod on its back slowly lowered, close to the gap below the deformed door panel.

A few seconds later, a palm stained with muddy water reached out from behind the door.

That hand was trembling uncontrollably, fumbling in the darkness, and first touched the nylon carry strap of the communication terminal.

unit 3 outside the door very cooperatively pushed forward gently by a small step.

The terminal was slowly dragged inside.

Immediately after, the voice channel in the command area suddenly removed all static, becoming exceptionally clear.

"Can you hear us?"

"We can hear you."

This time, they were no longer separated by the heavy deformed metal door panel and the noisy sound of water.

Although the voice of the man behind the door was weak, it finally reached everyone's ears completely.

"All four of us are here."

The medical team immediately fully connected.

Someone quickly instructed them on how to use hemostatic materials to re-apply pressure and fixate the injured personnel, while someone else had them prioritize covering the pinned personnel and head-injured personnel with high-molecular thermal blankets to prevent hypothermia.

The two bottles of drinking water were strictly required to be consumed in small, frequent amounts.

"Rescue personnel are already on the way, less than a hundred meters away from you," the commander comforted, "There are equipment brackets and deformed door panels outside the door; do not expend energy trying to dismantle them yourselves for now."

"Maintain communication."

"We won't leave."

It was quiet behind the door for a few seconds.

The man panted and asked, "Can your machine go eastward?"

"One has already gone over."

"Those two young inspector brothers, when they went out, they only carried a small flashlight in their hands."

The head of the command area said in a deep voice: "We are looking for them. Once we find them, we will let you know immediately."

"Okay."

At 5:27 PM.

unit 4 passed the pump house junction and headed eastward alone into the unexplored area.

The terrain of the maintenance tunnel began to show a downward slope.

Turbid accumulated water rushed from west to east, and the water depth gradually increased imperceptibly.

After advancing only a hundred meters, the black water surface had already submerged half of the machine's foot joints.

The distribution boxes on the wall had completely lost power, and short-circuit scorch marks still remained on several box doors.

Only the two beams of cold white light in front of unit 4 illuminated this narrow channel out of the darkness.

On the ground, scattered items appeared from time to time.

A crowbar.

An emptied first aid kit.

Half of a fluorescent warning stick snapped by external force.

Some of these things belonged to the original tunnel maintenance facilities, but some were extremely likely to come from the two missing inspection personnel.

unit 4 stopped at a corner of the wall.

The illuminating lamp swept across the wall; a yellow raincoat hung on the exposed steel bars that had burst out from the wall body, and the cuffs of the hem were severely torn.

A few strands of broken fibers still hung on the burrs of the steel bars.

The hem of the raincoat continuously dripped water onto the ground, and the dragging and wiping traces in the mud beside it had not yet been completely smoothed out by the water current.

"It hasn't been very long since they passed through here." Chen Yan quickly magnified the image, "These traces haven't been washed away by the water yet."

Jiang Lin's calm voice came from the communication link: "Look below the water current."

Chen Yan immediately switched to the low-position camera.

The turbid accumulated water was flowing rapidly eastward along the drainage ditch.

Below the torn raincoat, there were a few drops of slightly darker liquid being constantly dispersed and diluted by the water current.

Based on vision alone, it could not be confirmed whether that was blood.

unit 4 did not stop, continuing to advance deeper.

At 5:34 PM.

Fire Rescue Group 1 finally cut through the ventilation pipe obstacle at the nine-hundred-and-thirtieth meter mark.

Strictly following the safe route marked in advance by the robot, they quickly reached the white maintenance vehicle, and then entered the maintenance tunnel through the smashed maintenance door.

Between the rescue personnel and unit 3, there was less than a hundred meters of distance left.

The four people inside the pump house could already clearly hear the sound of metal cutting coming from outside.

The severely deformed door panel could not be pulled open directly by manpower.

The rescue personnel first had to carefully dismantle the metal brackets resting against the stress points outside the door, and then cut through the two hardest hinges from the door frame.

Before starting the cutting machine each time, the geological personnel required the site to pause and confirm that the vibration did not trigger a new structural response in the mountain.

Progress was very slow.

But the people inside knew that someone had already arrived outside.

This was more effective than any comfort in the world.

At 5:38 PM.

unit 4 arrived at the second maintenance door.

The heavy metal door body had completely detached from one side of the hinge, leaning diagonally in the middle of the maintenance tunnel.

On the right side, there was still barely a gap through which one could pass.

The last remote relay still remained at the entrance.

"Have unit 5 sent inside," the head of the headquarters said decisively.

Chen Yan's fingers hovered over the keyboard.

Unit 5 was the only backup platform on-site.

Once any machine in the confined space ahead experienced a mechanical failure, it was responsible for entering to drag back equipment, replenish relays, or directly replace the mission.

Putting it in now as well meant that the western entrance would no longer retain any complete backup forces.

Xu Man's cold and clear voice came from the headset: "I agree to deploy it."

Chen Yan looked up towards the direction of the camera.

Xu Man had already personally unlocked the physical fixing lock of unit 5.

"The fourth unit is currently four hundred and seventy meters away from the last stable relay; the packet loss rate is rising, and signal quality is dropping rapidly," Xu Man explained, "If we wait until it completely loses connection and then have unit 5 drive in from the entrance, there simply won't be enough time."

The head of the headquarters looked at the screen: "After the fifth unit goes in, do you have any other equipment to fill the vacancy?"

"There are no special platforms of the same level anymore," Xu Man answered truthfully.

Jiang Lin was looking at unit 4 on the screen.

unit 4 quietly stopped beside the second maintenance door.

The signal strength indicator bar in the upper right corner constantly fluctuated alternately between yellow and red.

There was still no human response coming from ahead, and it was getting closer and closer to the most dangerous landslide area on the eastern side.

If the last relay could not be delivered in time, unit 4 would trigger a retreat due to the communication protection mechanism before reaching the next search section.

Jiang Lin asked: "After unit 5 enters, who will stay outside to execute emergency towing?"

Xu Man said: "We still have the vehicle's built-in winch and manual towing soft ropes, but limited by length, they can only cover the area from the entrance to nine hundred meters."

"That means beyond the pump house, there will be none. If unit 4 and unit 5 are both trapped deep inside at the same time, we will be unable to physically recover them."

"Correct." Xu Man did not avoid this reality. "But when they were built and sent in, they were never meant to ensure that every single unit could retreat unscathed."

The communication channel was quiet for two seconds.

Jiang Lin looked at the oppressive footage transmitted back by unit 4.

That narrow maintenance tunnel, constantly dripping water, narrow, damp, filled with unknown fractures and collapses.

It was unknown how much passable road was left ahead.

The only difference was that this time, deep in the darkness, living people were waiting.

"Deploy unit 5," Jiang Lin finally spoke.

"Understood." Chen Yan pressed the confirmation key.

The last remote relay was secured to the back of unit 5.

Xu Man loaded a portable oxygen cylinder, an oxygen mask, and a bottle of drinking water into the mission pod.

At 5:41 PM.

Unit 5 strode with its six mechanical legs and entered the tunnel.

Several reporters authorized to film on the periphery stood behind the distant warning line, and their telephoto lenses keenly captured unit 5's retreating figure entering the tunnel.

Penetrating the misty rain curtain, the lens could only see that low gray machine stepping into the accumulated water, the red light on its fuselage flashing a few times before completely disappearing into the boundless darkness shortly after.

At 5:46 PM.

The cutting work outside the pump house door was finally completed.

Fire rescue personnel first fed a high-strength inflatable support pad through the narrow gap below the door panel, establishing a stable temporary support near the deformed equipment bracket.

After geological personnel confirmed that the latest round of rock stratum monitoring showed no abnormal displacement, several strong men worked together with one heart, starting to use crowbars to lift the heavy door panel.

The first gap large enough to accommodate a person appeared.

A weak, swaying flashlight beam instantly reached out from inside.

Someone shouted hoarsely from behind the door.

"Don't rush, don't push hard."

"The injured person's leg is still stuck underneath."

Two rescue personnel with relatively smaller builds crawled through the gap first.

The tragic extent inside the pump house was even worse than anticipated.

A metal control cabinet weighing several hundred catties lay collapsed on the ground, pinning the maintenance personnel's left leg tightly.

The accumulated water on the ground had reached near the calves, and several broken pipes on the wall were still continuously spewing cold water inward.

The rescue personnel had clear divisions of labor.

A medic first debrided and re-bandaged the head injury victim.

The rest of the team used support pads to secure the control cabinet, and then used a small hydraulic spreader to inch-by-inch create a safe rescue space between the cabinet and the ground.

unit 3 parked quietly beside the door.

The emergency lighting terminal it brought inside had been neatly placed beside the injured person.

Inside this desperate pump house, there was finally a stable and bright light source for the first time.

Five fifty-two in the afternoon.

unit 4 crossed the second maintenance door.

Its communication quality had dropped near the red warning line.

The images transmitted back to the command post began to experience brief mosaic stuttering.

In mid-air ahead of the maintenance passageway, a large section of heavy cable tray had collapsed.

The cable tray did not completely hit the ground; one end was firmly wedged in a wall crack, forming a dangerous slanted obstacle.

As unit 4 lowered its chassis and slowly passed underneath, the high-sensitivity sound collection module on its back suddenly captured a vague and brief syllable amidst the noise.

It sounded like someone was crying for help with their last ounce of strength.

Chen Yan immediately remotely stopped the vehicle, intercepted, and amplified that audio segment.

The background was filled with the sound of running water, the faint vibration sound of metal under stress, and the low-frequency noise of the machine's own joints operating.

After algorithmic filtering, that human voice appeared only once and then completely disappeared.

unit 4 immediately turned off its active cooling fans and entered the highest level of silent monitoring state.

All servo joints were locked and immobilized, and the front illumination brightness was reduced to a minimum.

A dozen seconds later, that voice appeared again.

This time, it was very close and much clearer.

"Is... there... anyone..."

Everyone in the command area straightened their bodies simultaneously the moment they heard this sentence.

"Lock onto the direction."

"Straight ahead, fifteen degrees to the left."

unit 4 released the lock again and started the motor.

After quickly crossing the cable tray obstacle, two beams of illumination suddenly swept toward the left wall.

That should have been a recessed equipment alcove used for storing maintenance tools.

But now, the entrance of the alcove was tightly blocked by the collapsed huge cable tray and heavy concrete chunks, leaving only an extremely narrow gap near the ground.

Behind the gap, there was light.

A weakly flickering flashlight beam.

unit 4 quickly approached.

unit 4 pressed its thermal imaging lens in front of the near-ground gap. In the narrow field of view, two human heat sources appeared successively, while the third was blocked by debris in front, with only a lower leg whose temperature was noticeably higher than the environment visible.

"Target personnel found." Chen Yan stared intently at the screen, his voice showing a clear fluctuation for the first time, "At least two people."

The head of the command post immediately grabbed the microphone and asked, "Can you confirm their specific identities?"

unit 4 moved close to the gap and turned on the speaker.

"This is the rescue robot, this is the joint rescue team."

"Listen up, people inside, please state your exact number out loud!"

A fit of violent coughing came from behind the gap.

Afterward, a young man shouted toward the gap with all his might.

"Three, there are three of us here, and we're all still alive."

At this point, all seven missing personnel had exact physical locations.

In the command area, someone heavily slammed their fist onto the tabletop, and someone immediately turned around to frantically modify the next step of the rescue deployment on the sand table.

On the white board, the last three names on the missing list were heavily marked as survived in red ink by the information officer.

"Report the condition of the wounded immediately!" Chen Yan continued to ask through unit 4.

"The driver says his chest hurts terribly and he can't catch his breath." The young man's voice carried a crying tone, "His legs can't move either, pinned by an iron frame."

unit 4's front probe showed normal gas detection data.

However, the temperature inside the alcove was relatively low, and the water level in the drainage ditch outside the door was climbing upward at a slow but irreversible speed.

Geological personnel overlaid and compared the alcove coordinates with the original structural map, their expressions changing drastically.

"The equipment alcove is located one thousand seven hundred and forty meters from the west entrance. Directly above it is precisely one of the hazardous areas where the surface micro-vibration response was most pronounced earlier."

Rescue personnel could not forcibly breakthrough along the main tunnel.

To arrive on foot from the maintenance passageway, one would need to pass through the pump house, the second maintenance door, and that crumbling cable tray in sequence.

What was even more troublesome was that the communication quality at unit 4's current location was showing a cliff-like drop.

Large green color patches appeared on the screen.

The voice was intermittent, mixed with harsh static noise.

"Where has the last repeater reached?" The head of the command post asked loudly.

"Unit 5 has just passed the maintenance vehicle's location, and is still four hundred and seventy meters away from the second maintenance door!"

"It's too late." Cold sweat broke out on Chen Yan's forehead.

unit 4's current signal was already on the verge of disconnection.

Once it crossed that threshold, according to the frozen underlying task rules, it would immediately stop all advancement actions and automatically begin to retreat backward.

Jiang Lin looked at the two figures leaning against each other in the image.

They had already found the people, and right now, the most important thing was by no means letting the machine continue advancing into the unknown. Rather, they must find every possible way to keep this life-saving communication link.

"unit 4, immediately retreat to find a position that can secure the fuselage and make a hard support." Jiang Lin issued a counter-conventional command.

Chen Yan understood Jiang Lin's intention and quickly checked the short-range link.

"The rescue personnel have confirmed your location, and a two-way communication and lighting terminal will be sent in through the gap. The robot needs to retreat twenty meters to establish a stable communication relay."

Hearing that the machine was going to leave, the people inside asked hastily and in panic, "Are you... are you coming back?"

"Rest assured, there will be another machine bringing supplies in."

unit 4 opened the push tray on the side of the mission cabin and delivered the two-way communication and lighting terminal to the front of the gap.

The terminal slid along the tray into the door.

The people inside immediately reached out and dragged it in.

The light of their original flashlight, which was running out of battery, had begun to dim.

When the new high-brightness lighting was turned on inside the alcove, the terminal camera finally allowed everyone to see the three people's predicament clearly.

The truck driver lay pale in the innermost part, with a severely deformed metal ventilation component pressing on his chest.

Two road patrol personnel squatted beside him, covered in mud and dirt.

One of their right arms presented an unnatural and terrifying bend, but he still gritted his teeth, holding up high with his left hand the lighting equipment that brought them hope.

unit 4 switched to a reverse gait and retreated backward.

Twenty meters into the retreat, an abandoned equipment concrete base appeared on the right side of the passageway.

The location of the base was slightly higher than the accumulated water surface, and the concrete roof slab above looked relatively intact.

unit 4 climbed onto the base, spread its six mechanical legs to the maximum extent, pressed them between the edge of the base and the hard wall respectively, and locked them through joint brakes, forcefully bracing its own fuselage into a suspended temporary communication base station.

The signal waveform recovered a precious bar.

Although not stable enough, at least it was not completely interrupted.

"Unit 5, full speed ahead."

Three minutes past six in the afternoon.

Inside the pump house, the first wounded person was finally successfully lifted out.

The head-injured maintenance personnel was supported on the left and right by two rescue personnel, struggling through the enlarged deformed door panel.

When he passed by unit 1 and unit 3 that had been guarding outside, although his body was trembling uncontrollably from the cold, he still reached out and gently touched unit 3's cold metal shell.

"Is this iron lump the one that brought water in for us?"

The rescue personnel patted his back: "Let's get out first, there are doctors outside."

The man nodded, asked no more questions, and with support, evacuated westward along the maintenance passageway, stepping heavily and unevenly.

The second and third maintenance personnel were escorted out successively.

Finally was the severely wounded person whose left leg was pinned.

Since he could not walk, the rescue personnel used a foldable torso-fixed stretcher to smoothly move him out of the pump house.

When passing through the ventilation pipe obstacle at the nine-hundred-and-thirty-meter mark, the team walked especially slowly.

unit 3 actively undertook the guard mission, walking ahead of the stretcher.

Its illumination light always pointed downward toward the ground, illuminating the footing for the stretcher bearers while avoiding direct strong light into the wounded person's fragile eyes.

Twelve minutes past six in the afternoon.

All four maintenance personnel left the pump house area.

Rescue Team 1, which was already extremely exhausted, began handing over and retreating.

Rescue Team 2 had previously entered the tunnel along the confirmed route, and at this time completed the handover with Team 1 outside the pump house, beginning to advance eastward.

Their target was the even more dangerous equipment alcove one thousand seven hundred and forty meters away.

From human safety standards, this route was still filled with the breath of death.

But now, three machines and two levels of stable communication relays were already distributed along the way.

The specific location of each obstacle was precisely marked on the electronic map.

The gas concentration, accumulated water depth, and structural changes of each section of the passage were supported by continuous data transmitted back by the machines.

After re-conducting a rapid assessment on the terminal, the geological personnel issued a strict limited entry permit.

[Personnel Entry Limit: Eight people]

[Eastward Advancement Endpoint: One hundred meters east of the second maintenance door]

[Beyond the endpoint, re-evaluation is required based on the on-site environment]

This permitted distance was still not enough to reach the equipment alcove directly.

The rescue team had to wait while walking.

Waiting for Unit 5 to accurately deliver the last repeater into place and completely illuminate the communication blind spot ahead.

Seventeen minutes past six in the afternoon.

Unit 5 passed the already empty pump house.

After escorting the first batch of wounded, unit 3 did not follow them all the way back to the safe cave entrance.

It stayed on the dry ground outside the pump house, handing over all the remaining polymer thermal blankets and two bottles of drinking water in its supply compartment to the passing Rescue Team 2.

Afterward, it turned its chassis, silently following behind the assault team to act as mobile lighting.

unit 1 continued to faithfully guard the key node of the pump house.

At this point, four machines were distributed linearly in this underground passageway stretching over one thousand seven hundred meters.

Twenty-three minutes past six in the afternoon.

Unit 5 arrived at the second maintenance door.

It opened the back release lock and placed the last blue relay beacon on the ground.

The repeater was fixed by strong magnetic suction above the inclined door panel, avoiding the water flow.

Powered on and started.

Protocol handshake.

First hop established.

Second hop established.

Third hop established.

On the main screen of the command post, unit 4's image, which had been in an intermittent and stuttering state all along, instantly restored silk-smooth high definition.

The three people inside the equipment alcove reappeared clearly on the terminal return image.

The road patrol personnel with a fractured right arm was holding the lighting terminal with his left hand, illuminating the face of the driver lying on the ground.

The driver's mind was still clear, but his breathing was becoming increasingly rapid, and his chest's rise and fall became more and more laborious.

The medical team immediately conducted intervention inquiries through the two-way communication terminal inside the alcove: "Driver, can you hear us? Does your chest feel like a sharp pain like pinpricks?"

"Yes..."

"Have the symptoms of breathing difficulty worsened?"

"Worsening... feeling suffocated..."

The medical staff's expressions instantly sank.

Because this was highly likely a pneumothorax caused by broken ribs puncturing the pleura.

They could no longer wait.

"Rescue Team 2, advance at full speed immediately." The head of the command post gave an order.

Eight fire rescue personnel quickened their pace and rushed into the most dangerous eastern section of the maintenance passageway.

They carried heavy demolition equipment, hydraulic spreaders, rigid fixed stretchers, and emergency oxygen cylinders on their backs.

Special machines could scout the way tirelessly, deliver life-saving supplies, and sacrifice themselves to establish communication.

But that final heavy metal component pressing on the driver's chest still required humans with flesh and blood to go in personally and lift it away.

Thirty-one minutes past six in the afternoon.

Rescue Team 2 had just all passed through the second maintenance door.

Inside the command area, a red curve on the geological monitoring data screen suddenly experienced a terrifying vertical lift. A harsh alarm sound instantly echoed through the entire tent.

Deep inside the tunnel, an extremely dull roaring vibration came.

On the main screen, the image transmitted back by unit 4 shook violently.

Above the equipment base, countless dust poured down like a waterfall.

Immediately following, with a loud roar, a whole piece of concrete lining on the right side of the passageway peeled off from the top.

The image transmitted back by unit 4 suddenly sank downward.

The concrete lining, wrapped with broken steel bars, cable trays, and a large number of fragments, smashed onto the equipment base in front of unit 4, and then slid downward along the inclined surface.

unit 4's six mechanical legs braked simultaneously, attempting to support the fuselage.

The impact still pushed it off the edge of the base.

A section of exposed steel bar pierced through the joint guard of the front left leg, and the drive line and encoder signal were interrupted simultaneously.

Another piece of concrete on the left side subsequently pressed down, pinning the mid-left leg and the fuselage belly together onto the edge of the equipment base.

The right side of the machine hit the wall.

The front right leg was jammed into the corner by the collapsed cable tray.

In less than two seconds, unit 4's central load-bearing structure had been sandwiched between the concrete base, the right wall, and the falling components above.

On the console, a large number of red alarms popped up simultaneously.

[Front Left Joint Cabin: Structural Failure]

[Mid Left Support Chain: Compression Limit Exceeded]

[Front Right Support Chain: External Constraint]

[Central Load-bearing Structure: Continuous External Load]

[Feasible Movement Space: Insufficient]

The underlying state machine immediately stopped all walking commands.

The front left joint driver was powered off, and the brake was released.

The center of gravity of the fuselage was reallocated to the remaining support points.

unit 4 did not fall.

The image stabilized after violent shaking.

But it could no longer move either.

Chen Yan pulled up the structural load diagram.

The two mechanical legs on the left were already buried in the rubble.

The front-right leg was stuck between the cable tray and the wall.

What truly caused unit 4 to lose its mobility, however, was not these three legs.

That piece of concrete lining pressing down from above pinned the central load-bearing frame firmly against the edge of the equipment base.

"PG-P04 central load-bearing structure under pressure."

Chen Yan's voice was taut.

"Front-left joint failed, middle-left and front-right are jammed by external components."

"Can we release the mechanical legs to get out of trouble?" Xu Man asked.

"They can be released."

Chen Yan looked at the constantly changing load distribution.

"But it's useless; the belly of the fuselage is pressed against the base, and the load above is still there. Even if we discard all three restricted mechanical legs, the main body still cannot be pulled out."

The geological personnel immediately said, "We cannot let the machine force a lift."

"That lining is now interlocked with the surrounding structure. If it forcibly breaks free, it may cause the upper part to continue falling."

unit 4 was only more than twenty meters away from the equipment alcove.

Rescue Group 2 was also advancing toward this place.

Any uncontrolled structural change could cut off the final rescue route.

Jiang Lin looked at the structural load transmitted back by unit 4.

Communication compartment intact.

Battery compartment undamaged.

Relay chain still stable.

The machine lost its mobility, but happened to be fixed by the fallen components at a position higher than the accumulated water. The rear communication module was not submerged, and the antenna maintained its original orientation.

"Cease extrication actions."

Jiang Lin said.

"Lock the remaining support structures."

"Shut down the locomotion system."

Chen Yan hit confirm.

[Active extrication: prohibited]

[Motion mechanism: locked]

[Communication relay: highest priority]

[Environmental monitoring: maintained]

[Remaining tasks: suspended]

unit 4 stopped all non-essential actions.

Half of the headlights were turned off, and the locomotion controller entered sleep mode.

It reserved the remaining battery power for communication, audio, and environmental monitoring.

Keeping the communication chain that passed through more than 1,700 meters of underground tunnels still lit.

The rescue personnel still stayed in place, not daring to act rashly.

Ten seconds.

Twenty seconds.

The geological monitoring curve did not continue to show a catastrophic rise.

Thirty seconds later, the geological personnel said, "No continuous deformation was captured; just now was closer to a local spalling."

He still stared at the monitoring curve.

"The risk has not been lifted. The designated team is allowed to proceed at the lowest speed, and touching the right lining is strictly prohibited."

In the command area, not a single person uttered a sound.

Everyone's gaze was fixed tightly on the monitoring curve on the large screen.

6:33 PM.

"Resume advancement along the original route."

Rescue Group 2 got up from the wall and continued advancing forward.

Unit 5 received the order, raised its hexapod gait to the upper speed limit allowed by the current route, and crossed the local spalling area full of rubble ahead of time.

When it passed by the trapped unit 4, it paused for a brief instant.

The two machines originally scheduled to be sent to the utility tunnel to perform routine inspections passed each other in the dark, dripping depths of the underground.

Unit 5 hugged the wall and passed through the narrow slit left by the collapsed components and the right side of unit 4.

Its illumination swept across the central fuselage pressed down by concrete, illuminated the three mechanical legs already buried in the rubble, and then continued to advance toward the equipment alcove.

6:37 PM.

Unit 5 arrived at the entrance of the alcove.

It opened the rear reel and released the cable head of the high-strength towing soft cable. The inspection personnel inside who could still move dragged the cable head through the gap and pulled it to the driver's side.

This soft cable could not be used to directly drag the injured personnel.

Its role was to tie down the loosened metal component pressing on the driver's chest, secured by the reverse pulling force provided by Unit 5 outside, to prevent the component from sliding a second time while rescue personnel were carrying out violent demolition.

Unit 5 opened the side door of the mission compartment and pushed the portable oxygen cylinder, oxygen supply mask, and that bottle of drinking water to the front of the gap.

Following the professional instructions transmitted by the medical team via the terminal, two inspection personnel carefully put the oxygen supply mask on the driver.

Drinking water was also passed in.

The driver barely opened his eyes and took just a small sip to moisten his chapped lips.

"How much farther are the brothers outside?" He asked through the oxygen mask, his voice muffled.

"Eighty meters, we'll be right there."

"Tell them to slow down." Every time the driver spoke, he had to stop to pant violently, his chest heaving up and down. "Don't... pin the other brothers here just to save me..."

Everyone in the command area heard this sentence.

The person in charge clutched the walkie-talkie tightly, staring at the constantly shortening distance numbers.

Rescue Group 2 was still sixty meters away from the alcove.

Forty meters.

Twenty meters.

6:42 PM.

The first fire rescue worker wearing a yellow helmet finally appeared panting in the wide-angle footage of Unit 5.

He bent over, passed through the collapsed cable tray, and came to the front of the gap in the equipment alcove.

The assault team members behind arrived one by one and quickly deployed their formation in the narrow tunnel.

Two people were responsible for using hydraulic props to secure the surrounding crumbling structure.

Two people set up heavy hydraulic expanders.

The remaining personnel waved their tools and began to dismantle the steel frames and concrete fragments blocking the entrance with all their might.

6:51 PM.

The first road inspection personnel finally crawled out from the cleared alcove entrance.

The second inspection personnel was pulled out shortly after.

Finally, there was the truck driver whose life hung by a thread.

The thick metal component pressing on his chest was tightened with a soft cable by Unit 5 outside, and at the same time slowly lifted millimeter by millimeter by the hydraulic expander.

Rescue personnel used a hard immobilization board to protect his chest and abdomen, moving him bit by bit onto the torso stretcher.

The driver trembled violently all over from the pain, but relying on his strong willpower, he never lost consciousness.

The moment the stretcher was carried and just crossed the threshold of the alcove, the footage from unit 4 experienced a minor shake once again.

Chen Yan's fingers instantly hovered over the abort button.

The geological monitor did not sound an alarm.

It was just that the residual structure of unit 4's front-left joint completely fractured, completely losing response.

The rest of the machine's systems were still stubbornly operating normally.

"All personnel have left the alcove," the frontline reported. "All members begin to withdraw along the original route."

7:08 PM.

The second batch of three rescued missing personnel crossed the second maintenance door under the escort of the rescue team.

7:26 PM.

They safely arrived at the pump room location.

unit 1 restarted, and unit 3 turned around with the team, continuing to act as guard and illumination.

As for unit 4, which had lost its mobility, the weak signal it emitted passed through the final relay at the second maintenance door, passed through the relay on the roof of the maintenance vehicle, and then passed through the obstacle relay at 930 meters, acting like an invisible lifeline sent all the way to the command vehicle outside the tunnel thousands of meters away.

In the footage on the screen, there were no longer any figures of human beings.

Only that collapsed equipment alcove and the waterlogged channel littered with debris remained.

Xu Man glanced at the remaining battery power in its status bar outside the tunnel.

Forty-one percent.

If the mountain did not suffer a new collapse to bury it, it could still maintain its communication state for several hours in this battered posture.

unit 4's central load-bearing frame was still locked down by the fallen components. Rescue personnel withdrew section by section along the maintenance channel, leaving only the environmental data transmitted back by it in the depths.

7:44 PM.

The first maintenance worker was carried out of the tunnel on a stretcher. Outside the cordon, a long-suppressed cry immediately erupted.

That middle-aged woman who had stubbornly stood in the rain holding her mobile phone suddenly rushed out of the temporary rest area and ran desperately to the side of one of the stretchers.

The staff on-site no longer tried to stop her, but gently reminded her not to touch the injured person's fractured leg under any circumstances.

The woman threw herself onto the stretcher, tightly grasping her husband's mud-stained right hand. Big teardrops rolled down, but she couldn't say a single word.

The man wore a large oxygen mask on his face, struggling to lift his mud-covered fingers to lightly touch the back of her hand.

Subsequently, the other three maintenance personnel were also sent out of the tunnel one after another.

8:03 PM.

Two road inspection personnel supported each other and walked out of the tunnel.

One of their right arms had already been properly fixed with a splint.

When the two stepped across that yellow cordon and returned to the world of the living, they stopped simultaneously and looked back deeply at the depths of the tunnel, which resembled the maw of a giant beast.

When they went in, there were five gray machines.

But now, only four were quietly withdrawing behind the rescue personnel.

8:15 PM.

The truck driver was carried out of the tunnel on a stretcher.

The medical team immediately pushed him into the ambulance, and portable oxygen continued to be supplied. After the doors closed, the joint headquarters began to check the final list of missing persons.

Inside the joint headquarters, the person in charge picked up a red pen to perform the final name confirmation.

[Maintenance personnel: 4 people, all found, all transferred]

[Road inspection personnel: 2 people, all found, all transferred]

[Truck driver: 1 person, found, transferred]

[Missing personnel: 0]

Seven people.

Not a single one was missing; all were brought back.

Outside the tunnel, the immense exhaustion brought after the extremely taut nerves suddenly relaxed.

Some people collapsed directly into the muddy water, lowering their heads and panting heavily.

Some took off their heavy safety helmets, wiping the rain and sweat on their faces over and over again with dirty cuffs.

Some took walkie-talkies and ran to notify other family members waiting on the periphery.

8:27 PM.

unit 1, Unit 2, unit 3, and Unit 5 stepped out of Qingya Tunnel one by one with heavy paces.

The polymer engineering shells of these four machines could no longer show their original smooth dark gray.

Thick muddy water, dried dust, and concrete fragments covered their precision fuselages like an ugly scab.

unit 3's supply compartment was already empty, and the towing soft cable on the back of Unit 5 still retained noticeable whitish stretch marks chafed by the edges of the rocks.

They formed a single file and passed through the cordon. According to preset task rules, the four machines went straight back to the two long-waiting transport vehicles, lowered their fuselages, folded their mechanical legs, and entered a dormant state awaiting manual inspection.

At this point, the rescue deployment on the west side of Qingya Tunnel began to contract.

The medical team escorted the wounded away.

Fire rescue personnel withdrew section by section along the maintenance channel.

Geological personnel re-demarcated the cordon range, marking everything east of the second maintenance door as a restricted entry area.

The next stage would no longer be search and rescue.

The site would first handle slope drainage, landslide body monitoring, and west lining reinforcement.

After external risks decreased, the obstacle-clearing team would advance inward section by section from both ends of the tunnel.

How much time was specifically needed, no one could give an answer.

Xu Man looked at unit 4 on the screen.

It was still pressed beside the equipment base by the fallen components, and the central load-bearing frame could not move.

The rear communication module kept working, and the footage of the equipment alcove and evacuation channel continued to be transmitted back.

Chen Yan turned to the obstacle-clearing plan.

The earliest construction area that could be entered was still more than 600 meters away from unit 4.

Separating them in the middle were the deformed lining, the water accumulation area, and the maintenance channel where local collapse had just occurred.

He flipped the plan back two pages and closed the terminal.

"We won't get there in a short time."

Xu Man nodded: "Collect all the data first."

Chen Yan began executing the task wrap-up.

Environmental records uploaded, search routes uploaded.

Load, gas, sound, and structural vibration logs verification completed.

Local temporary cache cleared, control zone re-locked.

[Task data: upload complete]

[Communication relay: maintained]

[Environmental monitoring: maintained]

[Locomotion system: shut down]

[Remaining battery: 40.7%]

unit 4 turned off half of its illumination.

The passage grew dark again, leaving only the status light illuminating a small piece of concrete on the edge of the fuselage.

Jiang Lin, far away at Building 17 of Tsinghua University Bauhinia, turned off the public screen.

Only the controlled link of unit 4 remained on the screen.

[PG-P04]

[Central load-bearing structure: under pressure and locked]

[Autonomous extrication: non-executable]

[Task data: uploaded]

[Equipment status: left on site]

Jiang Lin pulled up the subsequent engineering plan for Qingya Tunnel.

Drainage, slope reinforcement, lining support, segmented obstacle clearing.

unit 4 was located deep within the entire plan.

By the time the engineering advanced there, it might take several weeks, or even longer.

Chen Yan sent a message asking whether remote monitoring should be retained.

Jiang Lin replied.

[Retain until the link naturally interrupts.]

[All uploadable data prioritized for transmission back.]

A few minutes later, Xu Man added an equipment disposal status.

[PG-P04: Recovered with subsequent obstacle clearing of Qingya Tunnel]