Study On Stability And Support Of Surrounding Rock In Shallow Bias Section Of Jialongzhang Tunnel In He-hui-guan Expressway

With the rapid development of our country,the intensity of infrastructure construction has increased and the number of biased tunnels has increased.In addition,because of the line selection design,it is a common situation for the Lushan crossing that the asymmetrical load on the tunnel is more likely to occur in this shallow section,which seriously affects the safety and normal operation of the tunnel.The influence of the bias phenomenon on the tunnel construction is various,and it is usually reflected in the stress of the tunnel lining structure,the stability of the slope at the side of the tunnel,and the construction of the tunnel.Therefore,it is of great practical value and great social and economical significance to study the stability and support of the surrounding rock of the tunnel under the condition of shallow buried bias.Based on this,this article selects Jialongyu Tunnel of Hehuiguan Expressway in Guangdong Province as a research case.Based on detailed field surveys,physical simulation test methods are used to simulate the stability and support of surrounding rock under conditions of excavation disturbance.The structure also provides some reference and theoretical support for the construction of such tunnels.Mainly achieved the following research results:(1)Identify the engineering geological conditions and slope structure characteristics of the site.The site of the tunnel site is fully weathered granite and silty clay.The slope of the slope at the outlet of the slope is relatively gentle,generally 20o to 30o,and the center is relatively steep,generally 30o to 40o.At the bottom of the slope,there is a slope and valley,and in the middle there is a gully along the slope.(2)According to field survey results,a geological conceptual model and a physical model of the YK126+180 section of the Jialongyu tunnel were established.The conceptual model focuses on the characteristics of rock slopes and other characteristics of the slope.Based on the conceptual model,the slope is appropriately simplified,a physical model with a similarity ratio of 1:50 is established,and a similar material ratio test is performed using the orthogonal method.Rock and lining similar material ratios.(3)The experiment simulates the process of earth pressure change under the excavation conditions of the Jialongyu tunnel.The results of comprehensive tests compare the model earth pressure with the measured values: In the model test,the changes of the earth pressure in different parts of the left tunnel are affected by Left-distance construction disturbance has the greatest impact.The left part of the surrounding rock pressure is the leftmost part of the left rock arch,which reaches 5.5Kpa.The change of the earth pressure in different parts of the right hole is mainly affected by the right-hole disturbance,and is also affected by the left-hole disturbance.The maximum pressure of the surrounding rock on the right hole is in the right vault,reaching 5.8 Kpa;the excavation on the left hole causes the pressure of the surrounding rock in all parts of the left and right holes to show a sharp increase,and the left and right holes have different parts.There are some differences in the degree of influence of excavation: the left cavern has a maximum of 4.0 Kpa in the arch and the vault,and the right cave vault has a maximum of 2.5 Kpa.The excavation of the left cavern is on the side of the left cave.The influence of the right vault is the greatest;the excavation of the right tunnel leads to a decrease in the surrounding rock pressure in all parts of the left cave.After that,the left vault and the right vault on the side of the mountain have been stable.State,left hole The other parts are in a descending state at different rates,and all parts of the right hole have different degrees of increase;in the measured data of the surrounding rock pressure,the right vault is larger than the left vault greater than the right vault,and the measured curve rule corresponds to the right hole in the model.The curve of the process of excavating the left hole up the step to the step of excavating the right hole and the upper step of the excavation of the right hole leads to a sudden increase in the perturbation pressure curve when excavating the upper hole of the left hole,and then excavating the lower left hole and the upper left hole.When lining,the pressure curve tends to be stable.(4)The results of strain tests and measured strains of the lining of the comprehensive model test show that: in the model test,the changes of the strain(displacement)in different parts of the left and right holes were maximized under the influence of the excavation disturbance of the lower step of the right tunnel.The value is different.Any excavation step causes the same fluctuation of the displacement of all parts of the left and right holes.The excavation step has no effect on the displacement law of all parts of the left and right holes.The peak intervals of all parts of the left and right holes appear in the right hole guide tunnel and the right tunnel step excavation in the right hole.In this time range,the excavation of the right hole has a critical controlling effect on the deformation of the entire tunnel lining.Comparing the measured data with the displacement law of the right hole in the model,it is found that the curve corresponds to the curve of the process of excavating the right tunnel guide hole to the excavation of the right tunnel main tunnel,but the displacement of the three locations in the model.The size of the left arch is equal to the right arch waist is greater than the vault,and there are differences with the measured law.(5)The numerical calculation of the bare hole and the original supporting measures after the excavation of the tunnel is carried out.The stress cloud map,the maximum shear strain cloud map,the total displacement cloud map,the axial force distribution map of the bolt,the concrete bending moment diagram and the concrete shear diagram under the bare hole and the original support system are obtained.After two cases analysis,the numerical optimization of supporting measures is carried out.It is an ideal supporting scheme to reduce the distance of bolt ring direction and increase the length of rod body under the factors of surrounding rock properties(V),construction and other factors.