Construction organization of a tunnel in Chongqing Design
The construction organization design of a tunnel in Chongqing includes that the main stratum of the site is composed of Quaternary filling soil, Quaternary eluvium and diluvium, and mudstone and sandstone of Penglai Formation in the middle of Jurassic System, as revealed by engineering geological mapping and drilling. Stratum lithology is mainly: filling soil (Q4me); Eluvial deluvial loam (Q4el+dl) and Jurassic Penglai Formation bed rock (J3P) are interbedded with mud and sandstone. The basic characteristics and distribution range of engineering geology of each rock and soil layer are described as follows: variegated. It is mainly composed of clayey soil, strongly weathered mudstone and sandstone rubble, including construction waste. The particle size of hard debris is generally 50-500mm, accounting for 20-30%, slightly dense and wet. The exposed layer is 2.90~4.50 m thick, mainly distributed in residential areas. It is the backfill soil for engineering construction, and the backfill period varies from 3 to 10 years. Brown yellow, purple red. It contains weathered debris of mudstone and sandstone, in hard plastic shape, no response to shaking, and no luster. The exposed layer is 0.70~6.80m thick, mainly distributed in the slope zone of the entrance and near ZK4. Sandstone: gray white, purple red. It is mainly composed of feldspar, quartz, mica and a small amount of dark minerals, with a small amount of grayish green argillaceous nodules locally. Powder fine grain structure, medium thick to very thick layered structure, calcium and argillaceous cementation. The rock core in the strongly weathered zone is broken, mostly in the form of fragments, with low rock strength; The rocks in the weakly weathered zone are relatively complete, joints and fissures are relatively developed, the rock core is mostly columnar, and the rock strength is high; The rocks in the slightly weathered zone are complete, joints and fissures are relatively developed, the rock core is long in columnar shape, with hammering sound and high rock strength. After sampling for indoor test, the standard value of natural compressive strength of slightly weathered rock is 36.60MPa, the standard value of saturated compressive strength is 27.70MPa, and the softening coefficient is 0.76, belonging to soft rock. Mudstone: purplish red. It is mainly composed of clay minerals. Argillaceous structure, medium thick~thick layered structure. The rocks in the strongly weathered zone are broken, mostly in the form of fragments, with developed reticular weathered fissures and low rock strength; The rock in the weakly weathered zone is relatively complete, the rock core is mostly columnar, the joint fissure is relatively developed, and the rock strength is high; The rocks in the slightly weathered zone are complete, the rock core is mostly long columnar, the joints and fissures are relatively developed, and the rock strength is high. After sampling for indoor test, the standard value of natural compressive strength of slightly weathered rock is 12.3OMPa, the standard value of saturated compressive strength is 8.20MPa, and the softening coefficient is 0.67, belonging to soft rock. The engineering geological mapping and drilling revealed that no unfavorable geological processes such as fault structure, structural fracture zone and weak intercalation were found. The site is stable and suitable for tunnel construction. The seismic fortification intensity is 6, the building site is classified as Class II, and the design characteristic period is 0.35S. It is a general section that can be built. Based on the classification of rock strength and wave velocity, the surrounding rock is classified by considering the surrounding rock characteristics, environment and other factors. The relatively stable sandstone layer is Class IV; Thin to medium thick mudstone layer and sandstone, mudstone interbedding, poor interlayer combination, classified as Class III; The surrounding rock near the portal is classified as Class II due to the thin rock mass affected by the air raid shelter. Surrounding rock distribution from tunnel entrance to tunnel exit: etc. can be downloaded for reference
