Bearing Characteristics And Synergy Principle Of Tunnel Supporting System

For the excavation and supporting of the tunnel under condition with high self-stability,the applied method is very mature,and the safety risk is relatively small.The difficulty of tunnel engineering is mainly concentrated in the construction work of each procedure under condition of weak-broken surrounding rock.From excavation to support and then to putting into use,in the whole cycle of the typical tunnel,objectively the various types of supporting components form an organic support system,and the final form of the system shows a circular distribution in space.In the view of time,the combination of various support methods shows different stifffness characteristics,and the relationship of them is complicated.Therefore,it is necessary to do some research on the internal interaction relations of the system by studying the supporting properties of each support component.Based on plenty of document information and thoughtful analysis,the construction process of the support system is divided into three stages in time domain,and the tunnel circle model is established in the space.Thus,all kinds of supporting measures are included,and a complete set of supporting system is formed.On this basis,laboratory tests,theoretical analysis,numerical simulation and field test methods are adopted in the paper,advance support,bolt support,sprayed concrete arch,secondary lining,and the supporting characteristic of new materials are studied.The main research results are followed:1.The nesting circle model is established.The surrounding rock and support is considered as a whole,and it is divided into four organic parts:self-stability circle of original surrounding rock,preliminary reinforcement circle,initial support circle,secondary lining reserve circle.The internal force and deformation expression of the arbitrary circle model are given,and the contents contained in the supporting system are given.Through the analysis of time and space effect of the stress release of the surrounding rock,from any face section,the stress release of surrounding rock is divided into three stages:? advanced deformation stage,? rapid deformation stage,?slow deformation stage,and on this basis,the four types of the construction risk are divided,and it is considered that the safety risk controlling of weak-broken surrounding rock should be adopted in the ? stage.structure with different pressure coefficient are analyzed;It is considered that the bearing performance of the secondary lining in the section of the 350km/h—V high speed railway tunnel get the maximum when the lateral pressure coefficient is equal to 1.4;The reinforcement of the secondary lining in the high speed railway tunnel mainly plays a role of controlling the first principal stress(tensile stress)of the lining element,the effect of side pressure coefficient is the most obvious under the condition of small side and large side pressure coefficient,and with the comparison of the measured data,it is feasible to take the secondary lining as a safety reserve.5?The principle of cooperative action of the support system of the tunnel is analyzed.The concept of 'virtual tunnel face' is put forward,on this basis,the characteristics of support stiffness of each area in the direction of tunnel excavation are analyzed,and the possible failure types of various combinations are analyzed,the characteristic curve of the whole process of the composite support system is qualitatively given.Combined with the research conclusions about the supporting characteristics of the retaining structures in the previous chapters,the numerical model of composite support system is established,focusing on the analysis of coordination principle of the internal advanced support means?the preliminary reinforcement circle layer and cooperative action between the preliminary reinforcement circle layer and subsequent support circle layer,and the object,means and purpose of synergy of the tunnel support system are furtherly defined.