Application Of Displacement Back Analysis Of Taking Into Loosing Zone For Tunnel Engineering

Displacement back analysis has been more and more applied in geotechnical engineering. Because of the complexity of geotechnical engineering, many questions have been come into existence in the application of the displacement back analysis for tunnel engineering. This paper will by the numbers introduce the history and actuality of displacement back analysis, conclude the theory of displacement back analysis and FEM implement for elastic-plastic problem. This paper presents the application of displacement back analysis of taking into losing zone in tunnel engineering.Firstly, taking into account rock loosing zone in the tunnel excavating, the paper explains the necessity of displacement back analysis and analyzing model. The common used two-medium model is introduced. The general detecting methods of rock loosing zone is presented. According to the characteristic of gravel-cobble layer, the importance of using loosing zone model is introduced. How to calculate the size of rock loosing zone is put forward for engineering practice.Secondly, the three-dimensional model of tunnel excavating is established with ANSYS. In order to explain correcting problem of displacement as basic input information in plane strain problem. Normal computation for back analysis is introduced. The normal computation is used to check the effect of back analysis and also is applied to the informative tunnel construction. The general process of displacement back analysis is presented for the application in tunnel and geotechnical engineering.Finally, taking the constructing Ning-Chang Speedway as a case history, the computation of displacement back analysis is carried out. Taking into account rock loosing zone, the two-medium model is adopted in the computation. The elastic modulus of loosing zone from the back analysis is used to process the normal analysis to supervise the tunnel construction.