Application and Quality Control Technology of Diaphragm Wall in Deep Foundation Pit Support

Aiming at the common industry problems such as trench collapse, excessive deformation of steel reinforcement cage hoisting, and wall anti-seepage failure in deep foundation pit support of soft soil-sand interbedded stratum, taking a deep foundation pit project in Guangdong Province (working shaft depth 27m, receiving shaft depth 25m) as the research carrier, the optimization of diaphragm wall support system and the key technology research of super-large steel reinforcement cage (maximum weight 30t) hoisting were carried out. Based on the coupling of the modified Cam-clay model and Rankine earth pressure theory, a mechanical calculation model of the diaphragm wall considering the nonlinear characteristics of soil was established to optimize the wall thickness, reinforcement parameters and mud performance indexes. ANSYS was used to establish a three-dimensional mechanical model of the steel reinforcement cage, a stiffness control technology of "truss bar-shear bar collaborative reinforcement" was proposed, the transient force calculation formula in the dynamic hoisting process was derived, and the 16-point lifting point layout scheme was optimized. Combined with MidasGTS numerical simulation and field measured data, a trinity support system optimization method of "theoretical calculation-numerical simulation-field verification" was constructed. A composite support technology of "diaphragm wall + double row jet grouting pile + dynamic mud adjustment" was innovated. The research results solve the technical bottlenecks of deep foundation pit support and super-large component construction in soft soil-sand interbedded stratum, provide a theoretical basis and technical paradigm for similar projects, and have important engineering application value and popularization prospects.