Research On Range And Influencing Factors Of Surrounding Rock Break Zone In Fractured Soft Rock Stratum With High Geostress Tunnels

From the introduction of the surrounding rock break zone to the present,a large number of scholars have carried out a large number of field tests and calculations in engineering.However,most of these work are carried out in roadways or in hard rock,while in soft rock,there are still few studies on the scope of surrounding rock break zone.With the construction of the national railway,more and more high-stress soft rock tunnels are being encountered.For this special surrounding rock condition,the choice of supporting parameters of the project will change.It is especially important to use the break zone support theory to design and optimize the support.The determination of the loose break zone and the influencing factors of the break zone range become critical.Based on the Yuntunnbao Tunnel,Maoxian Tunnel and Yuelongmen Tunnel of Chenglan Railway,this paper conducts a series of studies on the range of break zone and its influencing factors by data investigation,field test,numerical simulation and theoretical calculation,which is the long-span of high-stress soft rock in the future.The test,provide reference to the test,calculation of range of surrounding rock break zone in fractured soft rock stratum with high geostress tunnels.The main work and conclusions are as follows:1.The formula and method of calculating the range of break zone by elastoplastic theory are introduced.The application of each plastic yield criterion is introduced.Combined with the field measurement,the elastoplastic theory is used to calculate the range of break zone.2.Introduced the test method and instrument of the break zone range and their respective advantages and disadvantages,and adopted the acoustic method to measure the loose circle range of the site.In the high-stress soft rock large-span tunnel,the loose circle range generally reached more than 10m..3.Using the numerical simulation method and determining the judgment basis of the loose circle,the calculation of the loose circle range for each·acoustic wave test section,the maximum difference between the obtained loose circle range and the field measured loose circle range is about 9%,confirming The feasibility of the numerical simulation method and the rationality of the discriminant basis.At the same time,the maximum difference between the theoretical calculation result and the field measured value is 2.3m.Therefore,it is not recommended to use the elastoplastic theory to calculate the loose circle range of the high ground stress soft rock tunnel.4.Using numerical simulation,the influence of buried depth,excavation radius and side pressure coefficient on the range of loose circle and its influence degree are analyzed,and under various influencing factors,the range of break zone is slowly increased to rapid development and finally re-entered the trend of steady development.