Development Of The Model Test Apparatus And Test Analysis About Underpinning Support

With the rapid development of urbanization in our country, the urban construction land is becoming increasingly nervous, and the protection of the existing buildings or pipelines around the excavation is becoming more common. Especially in the old city reconstruction project, to protect the surrounding buildings becomes the key to the design and construction of excavation. "Underpinning support method" is from the development of composite soil nailing wall, it uses pre-backing micro pile to bear part of the upper load, limit the settlement of superstructure; at the same time, the upper part of the building limits the top displacement of the composite soil nailing wall, and it is for the protection of foundation pit surrounding existing buildings a new form of excavation. It has broad application prospects and important scientific research value.According to the need of study on Underpinning support method, the paper designs a set of test device, and the device better completed the soil nail pullout tests, test pile capacity, composite soil nailing wall support model tests and Underpinning Custodian of model tests. In the course of the experiment, we have summed up a lot of experiences and lessons, including the problem in each connection node in the experiment, the position of the micro piles and the choice of the model materials. This paper introduces the test process of the model test and the matters needing attention for reference, and through the analysis of the test’s image data, a preliminary study on variation of the soil displacement field of Underpinning supporting structure.Finally, the paper uses the software FLAC3D to conduct numerical simulation in excavation based on the current buildings, and compares and analyzes the changing situation of soil displacement field of the numerical simulation and model test, the displacement of the surrounding buildings, the axial force of micro-pile and soil nailing etc, it Verify the accuracy of indoor simulation experiment and gets the relative advantages of Underpinning propping at last.