| Since the 1990 s,tunnel engineering has developed rapidly in China’s transportation system.During tunnel construction,blasting is used for tunnel excavation.Both the surrounding rock and the lining are damaged by the blasting impact.Therefore,this article considers some surrounding rocks and lining as a combination to study the differences.The mechanical properties of the surrounding rock lining combined body of different sizes,and then the support is optimized.In this paper,based on the principle of stress superposition,the loads on the surrounding rock lining structure of the tunnel are decomposed;the mechanical analysis of the surrounding rock lining structure of the tunnel is carried out according to the theoretical conditions of the thick-walled cylinder,and the calculation formulas of its radial displacement and axial displacement are obtained.In the experiment,the SHPB experimental device was improved,that is,a diameter reducing device was added between the incident rod and the transmitting rod to break through the limit of the previous impact test that can only be performed on the test piece with a diameter less than 75 mm.The specimens smaller than 200 mm were tested to obtain the stress waveform,and a large-section uniaxial impact test was performed to obtain the dynamic mechanical response of the annular rock mass sample of the surrounding rock lining structure under impact load.The obtained stress-strain curve and strength failure were obtained.Laws and modes of destruction.In terms of simulation,this paper uses the LS-DYNA software to simulate uniaxial impact tests where the thickness of the surrounding rock is constant,uniaxial impact tests where the thickness of the surrounding rock is constant,and uniaxial impact tests where the total thickness is constant.The impact test is mutually corroborated with the indoor experimental results and theories.The impact test process in which the thickness of the surrounding rock is unchanged under the confining pressure is simulated,and it is found that the strength of the combination increases with the thickness of the surrounding rock.In this paper,the design method of the main loads in the internal lining structure of the tunnel,the selection criteria of the lining,and the calculation method based on the dynamic load are determined in combination with the specifications of the tunnel support.It is found that the calculation of the support strength mainly considers the role of the static load and ignores the dynamic load.The effect of load;then analyze the failure law of linings and surrounding rock combinations of different sizes underthe influence of dynamic loads to explore the optimal ratio of surrounding rock and lining structure under dynamic loads to optimize the support and reduce dynamic Impact of load on tunnel safety. |
