A Study On Grouting Design Optimization And Quality Evaluation For Tunnels In Water-rich Fractured Rocks

When the tunnel is built through water-rich broken rock mass,the surrounding rock has poor self-stability,and engineering accidents are likely to occur under the action of water pressure.Necessary grouting measures must be taken to perform post-grouting reinforcement or advance pre-reinforcement to ensure tunnel excavation and operation During the period,there is sufficient security.This paper aims at the problems of grouting design optimization and quality evaluation for the excavation of water-rich broken rock tunnels.Based on numerical simulation,comparative test(control variable method),and orthogonal test methods,it is proposed to meet the newly built Zhengpantai tunnel of the Chongli section of the Beijing-Zhangzhou high-speed railway Technical quality indicators and economic benefits of radial grouting,pipe shed grouting and curtain grouting design optimization program.The fuzzy mathematics theory is used to establish the quality evaluation mathematical model of each grouting form of Zhengpantai tunnel,and the grouting design optimization effect is evaluated.The main results of the thesis are as follows:(1)Orthogonal experiments use the orthogonality of the design parameter set to select representative points from the test sample space.For the same number of trials,the number of optimized combination samples that can be evaluated far exceeds simple comparison Test,and have a higher degree of confidence.Orthogonal test results can determine the relative order of the influence of various parameters on grouting quality,and can be used as the basis for calculating the weight vector of grouting quality index.Based on the intuitive analysis,variance analysis and range test analysis of the orthogonal test results,the optimal design parameters for the radial grouting of the tunnel tunnel are obtained: the diameter of the excavated hole with the grouting ring thickness of 0.35 times and the elastic modulus as the original 5.0 times the rock,cohesion is 1.7 times the original rock,friction angle is 1.05 times the original rock,permeability coefficient is 1/50 times the original rock.(2)The optimal design parameters for the grouting of the pipe roof of the Zhengpantai tunnel are: the thickness of the pipe roof is 0.8m,the range of the pipe roof is 120° of the center line of the tunnel,?22 combined hollow grouting anchors are set at the vault,and ?22 ordinary mortar anchors are set at the side walls Rod.(3)The optimal design parameters of curtain grouting for Zhengpantai tunnel are: the curtain grouting range is 4m outside the contour of the upper step of the tunnel excavation(only for the tunnel excavation of the upper step curtain grouting).The floor is arranged with 40 ?108 steel pipe sheds.(4)The fuzzy mathematics theory is used to establish an evaluation model,and the quality evaluation results of the design parameters of radial grouting,pipe shed grouting and curtain grouting of the Zhengpantai tunnel are evaluated respectively,which shows that the quality is excellent.