Research On Asymmetric Supporting Mechanism And Reinforcement Techniques Of Large Deformations In Tunnels

Engineering practice shows that when the large tunnel deformation,its damage is often focused on one or more of the local surrounding rock,is not the whole section and holistic,deformation and failure characteristics have obvious asymmetry,the conventional symmetric supporting design often can not meet the requirements.These were the first to occur deformation and stress concentration area is known as the key parts.In addition in tunnel engineering,ground stress characteristics of tunnel surrounding rock form has significantly corresponding relationship;In-situ stress characteristics of surrounding rock failure modes,failure characterization,such as defining the macro qualification,but not all the failure mode can be consistent with those of tunnel,considering the complexity of underground engineering,ground stress characteristics is still one of the factors affecting tunnel failure mode,but it is a main influence factors.So this article on the existing research results,combine the stream asymmetric deformation and failure of tunnel engineering case,the in-situ stress of tunnel JiYaXing large deformation are analyzed.In nature,the connection between the solid and fluid is very tight,many materials have dual characteristics of the fluid solid,soft rock,the "materials" is no exception.For asymmetric large deformation of the tunnel,the selection of ground stress control JiYaXing large deformation model as the research object,through numerical simulation,analyzes the deformation process and the key parts,and then from the Angle of fluid dynamic asymmetric key parts of the large deformation analysis of deformation,deformation range,will affect to quantify the various factors of large deformation,adopt the method of weighted sum grading coefficient is defined and the asymmetric deformation degree classification;For asymmetric deformation occurred in the early years of the surrounding rock tunnel excavation,the existing of flexible retaining method(including lead stress release technology,contractible steel arch,pressure seam bolt type friction constant resistance)for design improvement,again on the bearing capacity of its constituent components related calculation;Finally,this paper discusses the asymmetric supporting principle,the mechanism of large deformation and the construction steps.The main work accomplished and the main researches achieved in this paper are described below:1)For asymmetric squeezing deformation tunnels,first of all,through the numerical simulation analysis,it is concluded that key parts;Again by softening of the plastic zone theory,determine the radius of plastic zone of surrounding rock control;Using soft rock fluid mechanics theory,calculate the stream asymmetrical deformation of the tunnel are the key parts of the deformation,deformation,deformation degree;The factors that will affect large deformation(displacement rate,elastic modulus and relative deformation,etc.)a quantitative classification,finally take the asymmetric deformation degree coefficient by weighted sum for grading coefficient,stream the asymmetric deformation degree of the tunnel for grading.2)Based on existing research results Pre-release technique of large deformation,through the related calculation of asymmetric deformation stress release plan in advance,drilling(drift),respectively,to carry on the design and relevant calculation.In view of the asymmetric deformation of stress release,choose drilling release plan process is more simple,more flexible,can be targeted to centralized layout of asymmetric key parts,this can not only achieve release effect,still can reduce the quantity,reduce the cost.So in the asymmetric deformation of stress release,give priority to choose drilling plan.3)For the asymmetric large deformation,using the flexible support reinforcement measures to achieve the purpose of "side to put the side resistance",in the traditional u-shaped contractible steel arch on the basis of the redesign,the ordinary type steel frame,in which joined the contractible segment to support key parts,this can not only provide enough bearing capacity,and can release the local stress,prevent supporting structure was destroyed,finally,the design scheme of steel bearing capacity is analyzed,contractible period for the relevant calculation and design.4)In this paper,in the end of split-set rock bolt joined the constant resistance unit,we design a new type resistance increasing large bolt for deformation,a new design scheme can better adapt to the tunnel surrounding rock deformation of the key parts,through the analysis of the bearing capacity design,calculate the limit bearing capacity of anchor rod and friction resistance,and has carried on the design of corresponding component,the constant resistance bolt has simple structure,each component link the advantages of controllable.5)At last,this paper discussed the principle,mechanism,construction steps of asymmetric combination supporting technology in tunnel,according to the asymmetric deformation division level classification coefficient,lists all levels of asymmetric deformation in tunnel supporting measures to design parameters,summarized the design process of asymmetric support in large deformation tunnel.Finally,in accordance with the design process of calculation and design cases,in theory analysis,at the beginning of the tunnel excavation using the flexible support measures to release stress of surrounding rock,it's good to control the deformation of surrounding rock,make more security and stability for reinforced structure in tunnel.