Measurement and Analysis of Soil Displacement During Construction of Ultra-Deep Diaphragm Wall Using Different Techniques

With the development of urban underground space to large depth, the application of diaphragm wall as the preferred enclosure structure of soft soil deep excavation is becoming deeper and deeper, and the maximum depth has exceeded 100 m. The influence of ultra-deep diaphragm wall construction on soil deformation has become one of the key factors in construction control. At present, the spatio-temporal analysis of soil displacement in the whole construction process and the influence analysis of different trenching processes are few. Based on this, this paper carried out two sets of field tests of diaphragm walls with different depth (50 m and 70 m) using different construction techniques (grab-bucket trenching, grab-hydromill combined trenching), and analyzed the spatio-temporal influence of the whole construction process on soil displacement. The measured results show that the soil displacement during the construction of the diaphragm wall has experienced three stages: “slow development in the trench period, rapid development in the static period, and a small recovery in the pouring period”. During the static period of the panel trench, the soil displacement increases rapidly, and the displacement increment is about 1 ~ 3 times, so the finish concrete pouring as soon as possible is conducive to soil deformation control. The recovery of horizontal displacement during concrete pouring is more obvious than that of ground settlement. After concrete pouring, the maximum ground settlement and soil horizontal displacement caused by single diaphragm wall construction did not exceed 10 mm. The influence of hydromill on soil displacement is significantly different from that of grab bucket, and soil squeezing occurs during milling. The construction of each section of the diaphragm wall has a significant effect on the soil adjacent to it, and a small effect on the area far away. The continuous construction of the diaphragm wall has a certain superposition effect on the soil deformation but not significant. The test results can provide reference for the quantitative evaluation of the influence of underground diaphragm wall construction on soil.