The Model Test Research On The Deep Foundation Pit With Pile-anchor Support

Deep foundation pit, as a newly elastic soil supporting structure, is widely used inurban construction. Its effect is remarkable in controlling foundation pit deformation.Many scholars have carried out studies concerning the supporting structure of this kindand the working mechanism of soil. They all agree that the soil stress of lateral pilecalculated from Classical Theory has much derivation from the actual pressure, however,the reasons of derivation and the mechanism that influences the derivations have notbeen figured out.In order to further investigate soil stress distribution of the lateral pile in pileanchor supporting structure after the excavation of soil, as well as the inner forcedeformation of supporting structure, the thesis designs a model test project according toSimilarity Theory, based on No.12Zhujiang Road deep foundation pit engineering as aprototype, and field test of pile anchor supporting structure as a starting point, stimulatesthe influences of soil unloading on supporting structure, and analyzes actual stressdeformation regulation of supporting structure by inspecting the deformation ofsupporting pile and soil stress of lateral pile in different excavation depth. The mainresearch work is as follows:Firstly, the model test results show that the soil stress of lateral pile is basically lessthan the theoretical calculation value before excavating foundation pit. After theexcavation, the soil stress begins to attenuate, and the soil stress between the twoanchors attenuates the most. The value of soil stress from the test is always bigger thanthat of Rankine’s active earth pressure. Compared with the theoretical value, theself-weight stress of soil between the two anchors will attenuate. Analyzing the reasons,it is because there exists a vertical soil arch in the space between the anchor supportingpoint and the back elastic zone and it effectively reduces the transmission of verticalstress to the deeper part, and then the soil stress appears to attenuate.Secondly, make similar shifts for model test results and compare them withprototype results, It comprehensively illustrates the variation regulation of lateral pile soil stress as soil unloading changes, and also makes up the disadvantages of soilstress-testing method in prototype test.Thirdly, build numerical calculation model of model test by FLAC3D, observe thesoil stress variation of lateral pile and inner force deformation of supporting structure,then compare the results with those of model test and analyze them. It has proven thereliability of the model test in monitoring data.