| China’s western development strategy has entered the stage of accelerated development,the highway tunnel industry has also developed rapidly,which also makes more and more tunnel across the mountains.In southwest China,there are a lot of tunneling tunnels that need to pass through karst rock sections.Karst rock tunnels are prone to bad geological disasters such as karst,and the stability of surrounding rock is poor.Therefore,it is of great economic significance and practical application value to establish a benchmark for controlling the displacement of surrounding rock to judge the stability of surrounding rock.In this paper,based on the collection and investigation of the monitoring and measurement literature of the karst rock tunnel during the construction stage,the displacement monitoring data of the karst rock tunnel of jiumian expressway are measured and collected to establish the database of the displacement monitoring and influencing factors of the tunnel.Based on the analysis of tunnel engineering measured data and mathematical statistics,the deformation law of tunnel surrounding rock and the influence of various factors on surrounding rock displacement are studied.The weight proportion of each factor is determined by combining analytic hierarchy process（ahp）with entropy method,and the reference value of surrounding rock displacement is determined.On this basis,BIM SPSS Modeler software was used to establish the association rule model of surrounding rock influencing factors-displacement reference value.The association rule obtained was combined with the statistical results and the comprehensive analysis of the existing norms to establish the optimal control benchmark of surrounding rock displacement of the soluble rock tunnel.Finally,the engineering application and test of the karst rock tunnel of jiumian expressway are carried out as an example.The main results are as follows:（1）According to the situation of on-site monitoring data collection of soluble rock tunnel,an improved monitoring burial point device is invented,which is characterized by the use of stainless steel shell to effectively protect the measuring point,prevent the damage of flying rock and enhance the stability;The device can be recycled,reduce pollution and save some time by connecting with throat hoop.The device is equipped with built-in LED lights to facilitate measurement and reduce indeterminate errors.It has been applied to jiumian high speed rock soluble tunnel project,and has achieved good application effect,which has greatly improved the collection of monitoring data.（2）Based on the analysis of the typical stable deformation curve of the karst rock tunnel,the stable deformation curve is divided into non-karst section and karst section according to the degree of karst,and the variation characteristics and rules of the steep deformation stage,the slow deformation stage and the basic stability stage are analyzed.The karstⅢlevel of surrounding rock stability time around 18d,Ⅳclass surrounding rock stability time around 22d,Ⅴclass surrounding rock stability time around 30d,curve trend approximate logarithmic function,belong to the plain.KarstⅣ,Ⅴlevel compared to the karst paragraphs need stable for a long time,Ⅳlevel of surrounding rock stability time,about 32d,Ⅴlevel of surrounding rock stability around 39d time.（3）Based on the displacement-influencing factors database of tunnel monitoring,the influence of each factor on the displacement of surrounding rock was statistically analyzed,and the weight of each factor on the displacement of surrounding rock was determined by combining the analytic hierarchy process（ahp）with the entropy method.According to the analysis results,the order of importance of the influencing factors of rock mass displacement of the karst rock tunnel is as follows:>rock hardness>rock mass integrity>advanced support>groundwater state>tunnel depth>initial support>tunnel span>formation lithology>excavation method>single-cycle footage.（4）The Apriori algorithm is used to mine the data of association rules of 7surrounding rock displacement influencing factors,and a total of 202 strong association rules of 4 geological conditions factors,1 design factor and 2 construction factors are obtained.Reveals theⅢ,Ⅳ,Ⅴclass surrounding rock under the corresponding geological parameters,construction methods and design parameters adopted in the corresponding;Analyzes the seven factors and four surrounding rock displacement of surrounding rock deformation parameters(peripheral convergence,vault subsidence,peripheral convergence（rate）,vault sink（rate）,association rules between the different factors affecting rock class-displacement prediction of association rules,support the displacement value and the speed of the mathematical statistics to get the reliability of the confidence interval,for optimization of lava tunnel surrounding rock displacement control benchmark has great significance.（5）based on the statistical analysis of 1001 monitoring sections of 7 solvable rock tunnels on jiumian expressway,and combined with the results of association rules for the influence factors of surrounding rock mass--displacement and the existing relevant specifications,an optimized benchmark for controlling the surrounding rock displacement of solvable rock tunnels on jiumian expressway was established.The results are as follows:Ⅲ,Ⅳ,Ⅴperipheral convergence of surrounding rock,the vault subsidence displacement permissible value U0 is respectively 69 mm,60 mm,90 mm,75 mm,105 mm and 84 mm;Ⅲ,Ⅳ,Ⅴperipheral convergence of surrounding rock,vault subsidence rate permissible value where V0 were 3.0 mm/d、3.0 mm/d,4.0 mm/d、3.0 mm/d,4.0 mm/d、3.0 mm/d.（6）The improved displacement monitoring embedment device was applied to jiumian high-speed tianchi tunnel.The application results show that the improved displacement monitoring embedment device has a certain practical significance.Compared with the conventional embedment device,the improved displacement monitoring embedment device has the advantages of being recyclable,having a long service life,reducing pollution and saving the time of making up points.The application results of the optimized displacements control datum for the displacements of rock tunnels show that the optimized displacements control datum is more suitable than the pre-warning of the displacements of the original rock,which is of great significance for guiding the field construction. |
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