The earth of the Northern ridge did not yield easily. It was a dense, stubborn mix of slate-gray clay and frozen pine roots. Long before the morning fog had even showed, the five stood in the damp central clearing.
There were no laborers here yet; Mu Wei took the first strike. His heavy iron-tipped pickaxe swung in a powerful, clean arc, embedding itself deep into the frozen crust with a dull, echoing thunk. He wrenched the handle sideways, tearing free chunk of earth. Beside him, the two brothers moved into the space, their bodies working in a rhythmic, unhurried cadence as they dug the trench-work.
Bai Ling was left at home with the kids and the unconscious man. The five of them were enough to dig work. They were digging the underground cellar and escape route. A massive, subterranean vault directly beneath the main living pavilion and connecting outward through the perimeter.
"Steady on the Northern edge"
Su Xiao murmured, her voice low as she held a small oil lantern close to the excavation line. She traced the geometric stakes she had driven into the mud the night before.
"The cellar walls must line up exactly with the load-bearing pillars above. If we drift even two inches to the left, the weight of the roof timber will split the foundation stone when the ground thaws"
"We want the bedrock", Mu Wei explained from the dark of the trench, his voice thick with exertion.
"Bedrock doesn't shift when the spring rains turn the mountain into a swamp"
The men grunted in understanding as they dug deeper. Su Xiao and Shi Dong took over hauling the excavated clay with a heavy wicker basket. Their muscle straining under the load as they dumped them into the interior courtyard where it would be used later.
By the time the third watch of the morning arrived, the cellar floor was locked flat against a shelf of solid granite six feet below the surface.
"The tunnel segments", Mu Wei called out as he looked up from the pit.
Su Xiao carefully rolled out the thick, high-fired terracotta they had hidden under layers of dead leaves and lowered them. He and the brothers received them in the trench, their hands slick with mud as they guided the heavy clay tubes end-to-end along the narrow ditch leading out from the cellar's western wall.
She handed down a clay pot mixture simmering with a pungent smell of boiled pine resin and earth-tar.
"Seal the seams thrice over", she instructed gently.
"The mountain water will try to find it's way in. If the resin cracks, the tunnel floods".
Mu Wei nodded as he smoothed the sticky, black sealant over the clay joints with absolute thoroughness, taking his time. The tunnel lead outside the perimeter to the forest. To unassuming people, it was a granary cellar for storing winter food.
But Su Xiao and Mu Wei knew exactly the mechanism installed and it's location. That way, the could sneak out unoticed safely into the mountains. Once the pipe was sealed and locked into the dirt floor, the structural arch followed.
"If we stack raw dirt over this clay, the weight of the earth alone will crack the terracotta within a month. So these stones will carry the burden".
The jagged river boulders which were hauled down from the mountains were then hand-wedged against the solid mud walls leaning them towards each other at a sharp, precise angle until they met directly over the top of the pipe like a natural triangular arch.
The downward pressure of the earth would be forced outward, driving the weight into the solid bedrock walls of the trench and leaving the hollow escape tunnel completely untouched below. Just as the final locking stone was wedged into the apex of the arch, the distant sound of voices echoed from the lower mountain trail.
Mu Wei and the rest climbed out and dusted themselves. Su Xiao handed them the boiled ginger water she brought from home.
Putting on their coats, they went to meet the laborers. As the laborers stepped into the clearing, they noticed a deeply excavated soil resting in the ground.
The inquisitive looks from the men were not subtle. Mu Wei cleared his throat to give a brief explanation.
"That's a cellar for the winter granary. Enough talking. Today, we build the perimeter walls. Get moving!"
With that explanation, it because clear. The laborers lost interest and focused on the day's work. They were immediately divided into teams. Some were taken by Lu Tui to haul massive granite blocks from the timber clearing to the trench line.
"Move the stone carts to the western line!"
The first team hauled granite blocks towards the trench using thick hemp ropes. The second team lead by Lu Dan were in charge of laying stones. The third team would be in charge of transporting the sticky-rice broth down to the site.
Su Xiao took over the mortar pit as massive cauldrons bubbles over fire; cooking the sticky-rice broth and slaked lime for the siege-proof concrete. Bai Ling had arrived with kids and handled the laborers food. As the granite blocks reached the bottom, they used iron crowbars to pry and guide it into it's exact place over the hidden boulder arch. It settled with a heavy, hollow thud that vibrated straight through the soles of the feet.
It sat perfectly over the hidden arch, completely anchoring the secret escape without touching the clay pipe. The steaming rice-lime mortar was passed down in the wooden buckets and carefully poured into the deep seams between between the granite and trench walls, filling the gaps and sealing the foundation from mountain moisture.
By the time the sixth block was set, they were all sweating profusely in winter. After thirteen hours, the subterranean base only knee-high above the dirt and tracing the boundary of the land was seen. As the day's end of work sound was heard, the laborers sighed in relief. The workers gathered the cloaks, rubbed their aching lower backs and lined up at the kitchen side where they were distributed hot ginger water and thick slices of coarse barely bread as bonus for fierce work.
The workers dissatisfaction were swept away as the received their wages and had extra food. They carefully made their way down the mountain, their voices fading away.