The major reinforcement work in the first and second sections involved implementing retaining walls and roof supports and anchoring large areas. The cliff is discontinuous with many structural entities. The interior has undergone weathering, fracture, cracking, and cutting, with independent and partially independent blocks being formed. However, these blocks have their own self-supporting force and this needs to be taken into consideration in the reinforcement.
In reinforcing the cliff rock in the first and second sections, different techniques were applied in accordance with the different conditions of each cave. Three levels of caves in the vertical direction were grouped in the first working section. The front chambers of these caves had collapsed, and some had very thin roof rock. Stress-relief cracks had occurred inside many of the caves, making it unsuitable to insert bolts into the rock. Retaining walls were the principal means of reinforcement used, supplemented with bolts. Archaeological data were used as references to restore parts of the front chambers to their original shapes. Concrete mortar was poured on-site for use in the restoration of the entrances and walls of the caves. For example, portions of the front walls of Caves 2-6 were anchored to the wall of the cave entrance and to the cliff rock in a single entity by bolts, thereby combining partial restoration and reinforcement.
The caves in section 2 are scattered. The front chambers of these caves had collapsed, whereas the rear chambers remained intact. Most of these caves are located at the base of the cliff. For this reason, the anchoring technique used for large areas was principally applied in this section. Bolts 16 mm in diameter were spaced 1.5-2 m apart and arranged in a plum-blossom shape with an anchor depth of 2-4 m. Where cracks were present, the anchor depth was about 0.5-1 m beyond the location of the last crack.
One case that deserves particular comment involved a large, precarious rock about 10 m high, 3 m wide, and 2 m thick that constituted the wall between Caves 33 and 34. A crack about 10-20 cm wide ran through the rock from top to bottom. In front of the rock were some remains from the front chamber that were used as an archaeological reference point. There was no alternative but to preserve this rock, as it could not be ignored for structural reasons. In the course of the work, two waist frames were installed in the middle of the rock to attach it tightly to the cliff in back and prevent it from collapsing during drilling. Bolts were installed in a plum-blossom pattern. To prevent further erosion by rainwater, the crack in the rock was filled with concrete mortar and the surface sealed with cement. This not only eliminated the dangerous condition, but it also preserved the historical evidence of the original shape of the grotto.
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