Study On Stability Of Surrounding Rock For Construction Of Large Cross-section Tunnel On Expressway

Over the years,our country’s overall development level has been ranked in the world’s top echelon,driving the rapid development of China’s highway traffic construction,and the level of highways has been continuously improved;at present,the entire country’s expressways have been built and operated for more than 130,000 km.The number of various types of highway tunnels is also increasing.Large-section tunnels have become an important part of China’s highway tunnels.Therefore,the study of the stability of surrounding rock for the construction of large-section tunnels has both theoretical and research significance.It can be used to guide engineering practice,improve the safety of project construction,speed up the progress of construction,and save a portion of project investment.In this paper,through the engineering practice of Xiaotuanshan and Yangzong Tunnel of KS expressway in Yunnan Province,the stability study of the construction of surrounding rock for the construction of the two three-lane large-section tunnels is carried out;the main research contents are: follow-up investigation on the construction geology of large cross-section tunnels.Comprehensive analysis of stability analysis of surrounding rock masses,construction monitoring measurement and feedback analysis of large-section tunnels,and numerical simulation analysis and research of large-section tunnel construction dynamic processes.The main results and conclusions obtained are as follows:Firstly,through the on-site construction geological tracking investigation and monitoring analysis,the main joint fracture development characteristics affecting the stability of the rock masses of the two large-section tunnels of the KS expressway Xiaotuanshan and Yangzong Tunnel were identified;then,the application software was used to analyze the characteristics.The stability of the surrounding rock mass of tunnels in typical tunnel sections of these two tunnels;through the systematic summarization and analysis of construction monitoring measurements and data of three-lane large-section tunnels,the two large-section tunnels Xiaotuanshan and Yangzong were drawn.The maps of deformation displacement and time characteristics of surrounding rock show that the deformation stage,rate of change,stabilization time,and final evolution of the surrounding rock show certain regularities;detailed studies have shown that the deformation of surrounding rock of the tunnel is affected.There are many major factors,including the surrounding rock grades,types of rock structures,excavation methods,and supporting methods;at the same time,the tunnel displacement anti-analysis intelligent commercial software(BMP90)is used,and the Yangzong tunnel and Xiaotuanshan are analyzed in reverse.A number of valuable sections of the tunnel have been obtained,and a number of valuable physico-mechanical parameter values of the surrounding rock have been obtained,thus providing favorable advantages for dynamic numerical simulation analysis.in accordance with.By carrying out the above work,the monitoring data obtained were analyzed and it was negated in a timely manner to delineate between the Permian Shaoshan basalt(P2β)and the underlying Fuyang New Limestone(P1y)in the Yangzong tunnel in situ survey and construction drawing design report.The mistaken recognition of the fault(belt)contact is considered to be a normal eruption(spill)contact relationship,and a correct prediction of the lithological boundary line position is made.This research result was adopted by all parties involved in the construction and confirmed in the subsequent engineering construction practice.The direct benefit was to change the corresponding design of Grade V surrounding rocks from the original tunnel to the IV in the tunnel.The surrounding rock,with a total length of 347 m,was changed;at the same time,a comparative analysis of the dynamic construction process under the different excavation methods of the Xiaotuanshan and Yangzong tunnels resulted in the conclusion that,on the premise of guaranteeing construction safety,although the design unit recommends The CD method can show certain advantages compared with the seven-step construction method in controlling stress distribution of surrounding rock,deformation characteristics of surrounding rock,development of plastic zone,etc.,but in practical operability,construction process and process,construction progress The seven-step construction method such as protection and construction cost also has obvious advantages.Therefore,the numerical simulation analysis confirms that the seven-step construction method used in actual construction is completely feasible,which provides relevant basis for the reasonable selection of construction methods.Through the above research and the conclusions drawn from the research,it provides some references for determining similar and correct construction methods and engineering measures for similar projects,accelerating construction progress and saving construction investment.