Study Of Base Layer Model Experiment And Construction Settlement Analysis In Immersed Tube Tunnel

Study of construction settlement and the base layer settlement is an important part of the immersed tube tunnel subsidence research. Have a better understanding of rules in construction settlement is helpful to improve construction quality and ensure safe operations. In this paper, construction affect and settlement rules are researched by analyzing the measured data and cases statistical. A shrinking size model test is taken to simulate the underwater environment as well as the base layer formation and compression under the construction techniques. The base layer compression characteristics under different conditions is tested in the model test. Basing on the research settlement reasons and control measures is summarized.The main conclusions and innovation are as follows:(1) The construction settlement has55.9proportion of the total settlement in average. The longitudinal settlement is very uneven during construction but relatively continuous after construction, the construction uneven will be enlarged after construction.(2) There is significantly a break point in the variation between settlement and time during construction which means the base layer and under soil complete compression differently in time. The uneven settlement during construction affected much by the construction process and cumulative settlement.(3) The compression modulus of sand and gravel base layer is3.26MPa in the simulated condition in average, and the interaction produces approximately4.4-fold increase of the compression modulus which related much with the base layer density.(4) The back silting in the base tank played a similar role of lubricant during compression which can expand compression unevenness, and only a few exist back silting influence is very evident. The base layer compression modulus with back silting is about0.6times that of without silting under simulated conditions.