Research On The Design Method Of Active Underpinning Of Underground Excavation Station Close-fitting And Underpassing Existing Station

Along with our country economic development impetus urbanization,the increasing demand for urban rail transit,new subway tunnel with the existing subway tunnel intersection are also more common,so the two cross transfer of more and more,in order to minimize the transfer distance,under the new station generally take in both the station construction method.With the progress of construction technology,the settlement control standard of the existing building(structure)is becoming more and more strict.In order to meet the requirements,active jacking underpinning is generally adopted for reinforcement.However,at present,the research on active jacking force is still not clear,which results in the displacement compensation control and no stress control,which will cause the phenomenon of existing structure damage caused by excessive jacking force.Therefore,it is urgent to put forward the calculation method of active jacking force to realize the dual control of displacement and active jacking force in jacking design.To this,this article relying on Beijing metro line 6 apple orchard station in line 1 and line10 of Beijing metro line 16 wear suzhou street station of actual engineering,adopted the literature research,theoretical analysis,the research methods such as field measurement and numerical simulation,both the station are analyzed in detail the relation and active top lift,calculation of the lift force of active method is proposed,Based on this,an active underpinning design method is established and verified.The research has achieved the following results:(1)The safety control measures used in underpass construction are summarized through investigation and research,and are divided into active control measures and passive control measures according to the thickness of the embedded soil.Through numerical simulation proved the failure mode of soil,and reveals the influence of the factors of soil damage,puts forward the theory of clip in soil damage mechanics model and evaluation method,and on this basis will clip in soil failure mode is divided into totally part failure mode and failure mode,in view of the complete failure mode,need to adopt active supporting measures,for part of the failure mode,Passive support measures are required.(2)for the clip soil destruction of under wear type,relying on the apple orchards and suzhou street station of the numerical simulation,using the research method of the control variables,revealed that one thousand catties bumps and grouting support + top litres under the two methods of active underpinning both station settlement rule,proved that the active top lift can effectively control both the settlement of the station,The relation between the active jacking force and the settlement of the existing station is clarified,and the principle that the existing station can play a blocking force transfer is obtained.On this basis,the rational range of the active jacking force is proposed by analyzing the relationship between the active jacking force and the settlement and stress of the existing station.(3)Based on the theory of beam on elastic foundation,a theoretical calculation model of close-sticking underpenetration is established.The corresponding relationship between the existing station settlement and the active jacking force is obtained through the Mindlin solution calculation formula and the differential equation of beam disturbance curve on elastic foundation.On this basis,the design methods of jack active underpinning and screw +grouting active underpinning were proposed based on suzhou Street station and Pingguoyuan Station,and the design method of dual control of existing structure displacement and active jacking force was established.Aiming at the design method of screw + grouting,the relationship between screw stiffness and settlement is obtained according to the stiffness calculation formula,and the synergistic jacking mechanism of screw and grouting is obtained by combining the relationship between grouting pressure and settlement.The grouting design process and the influence law of screw stiffness and grouting pressure on settlement are proposed.