Research On The Internal Force In The Soil-nailed Supporting System

The force mechanism of soil nail and its characteristics are always the key in the soilnailing supporting research field. In this paper, through modeling of basic forcebehavior of soil nail and taking the effect of sliding plane on the supporting systeminto account, a meaningful study is carried out. The studying results show there is bigdifference in the force mechanism of soil nail between the both sides of the slidingplane; in the sliding area, there is active earth pressure; and in the stable area, there isstatic earth pressure. After computing and analyzing the internal force of soil nail inthe sliding area, it finds that there is some shortcomings in the present design theoryof soil nail anti-pulling force, a new concept is proposed. That is the supportingsystem produces anti-pulling force. The total anti-pulling force derived from thesupporting system originates from two parts: the soil-nail interaction and theself-supporting ability of soil. The supporting system firstly adopts the anti-pullingforce produced by the self-supporting ability of soil. When the anti-pulling forceproduced by the self-supporting ability of soil is beyond the requirement, then drivesthe nail-soil interaction to devote its function to the stability. In this paper, the authorconstructs a model for analyzing the basic force behavior of soil nail and deducesequations for calculating the two kinds of anti-pulling force of the supporting system,and conducts some calculations in a project. Incorporating the in-situ stress test, adetailed discussion about the force mechanism of soil nail in the supporting system isgiven. In the same time, FEM simulation of design in this project is presented.Thefollowing conclusion is gotten:The physic properties of soil strata have influences on the internal force of soil nail;the anti-pulling force of the supporting system is provided both by the self-supportingability of soil and the nail-soil interaction; the internal force of soil nail is changingwith the process of excavation; the internal force is growing bigger along the soil nailuntil it reaches to a certain magnitude, then it begins to reduce. There is a precisemaximum value. The maximum value appears at the position of the failure place ofsoil mass; The relation of the internal force and the buried depth of soil naildemonstrate the force on the mid soil nail is bigger than the force on the upper &bottom soil nail; The effect of the exterior environment on the internal forces of soilnail can't be neglected.