Deep Foundation Pit Support and Groundwater Control Method in Soil Rock Combination Strata in Lanzhou Area

Lanzhou area is a typical valley basin landform with two mountains and one river, the upper part of the area is Quaternary loose deposits and the lower part is Neogene weathered bedrock. The basic distribution of soil-rock combination strata and the distribution of groundwater in Lanzhou area was introduced. According to the cementation degree, water permeability, and uniaxial saturated compressive strength characteristics of the lower weathered bedrock, the soil-rock combination strata was divided into two types, The upper part of one combination is a loose accumulation layer, and the lower part is a weakly permeable to moderately permeable sandstone. The upper part of the other combination is a loose accumulation layer, and the lower part is an impermeable sandstone. For two types of soil-rock combination strata with completely different properties, the selection of supporting structure and groundwater control system for deep foundation pit engineering was summarized, and a typical case of deep foundation pit design in two types of soil-rock combination strata was given which provides a good reference for the design and construction of deep foundation pit engineering in similar strata.