Analysis And Research Of Broken Zone Of Tunnel Surrounding Rock Based On H-B Criterion

During excavation of tunnel, broken zone of surrounding rock exists due to the surrounding rock stress redistribution caused by disturbances of blasting. The occurrence and development, as well as stability of broken zone determine the stability of surrounding rock and the complexity of support, the larger the broken zone, the poorer the stability and the harder for supporting.In this paper, H-B strength criterion of broken zone was deduced thickness calculation formula for distribution range of broken zone were studied, the main contents and conclusions are as follows:(1) Research broken zone theory is put forward and development, analysis of the advantages and disadvantages and the applicability of the calculate the relaxation zone of broken rock thickness formula of the elastic theory, the plastic and elastic-plastic theory. (2) Theoretical research is performed first with the rock strength estimation method in H-B criterion, corresponding parameters are estimated with specific parameter selection method, substitute the parameters into formula equation set to calculate the radius of plastic zone of surrounding rock, and then apply the radius to the thickness calculation of broken zone to determine the distribution range of broken zone of tunnel surrounding rock. (3) In this paper, a tunnel engineering is taken as example, typical sections ZK204+930 and ZK205+490 of the tunnel is selected, conclusion is reached through the method in combination of theoretical calculation, numerical modeling and field measurement of surrounding rock:scope of broken zone of grade Ⅳ surrounding rock is 0.8-1.6m, and that of grade Ⅳ surrounding rock is 0.8-2m. Analysis showed:there is good consistency in scope values of broken zone obtained through theoretical calculation, numerical modeling and field measurement. Proved that the calculation formula of circular section tunnel surrounding rock broken zone based on H-B criterion, can be calculated accurately and the broken zone, reasonable selection of support parameters, supporting type and provide a theoretical basis to determine the supporting construction time, have a good applicability in practical engineering applications.