Study On The Characteristics Of Rockburst Under Themo-mechanical Conditions And Its Prediction Methods

Lalin Railway Sangzhuling Tunnel is a special long-distance railway tunnel in the Tibet Autonomous Region.The tunnel is currently connected.Before construction,there are many obvious characteristics of high ground stress.How to distribute the geostress field in the tunnel crossing area and whether or not the rock blasting activity has occurred has become a major technical problem that engineers and technicians are concerned about.During the construction of the tunnel,high geothermal disasters occurred,which seriously affected the safety of construction personnel and equipment.According to the research of many scholars,the temperature has a certain control over the rock burst,so when the prediction of rock burst under the action of thermal-force,should take into account the effect of temperature.At present,the prediction of rock burst under thermal effects is almost blank,and there is little research.This article is based on the previous research on the prediction of rock burst and rock burst,combined with the field survey results of the Sangzhuling Tunnel,through numerical simulation software,and statistical analysis.Theoretical research and other methods are used to study the stress field,temperature field,geological structure,rockburst damage characteristics,thermal-force rockburst stress characteristics,and excavation section of the Sanzhuling tunnel.The main research results are as follows:Lalin Railway Sangzhuling Tunnel is a special long-distance railway tunnel in the Tibet Autonomous Region.The tunnel is currently connected.Before construction,there are many obvious characteristics of high ground stress.How to distribute the geostress field in the tunnel crossing area and whether or not the rock blasting activity has occurred has become a major technical problem that engineers and technicians care about.During the construction of the tunnel,high geothermal disasters occurred,which seriously affected the safety of construction personnel and equipment.According to the research of many scholars,the temperature has a certain control over the rock burst,so when the prediction of rock burst under the action of thermal-force,should take into account the effect of temperature.At present,the prediction of rock burst under thermal effects is almost blank,and there is little research.This article is based on previous researches on rock burst and rock burst prediction,combined with the field survey results of the Sangzhuling tunnel,and numerical simulation,statistical analysis and theory.Research and other methods have studied the geostress field,temperature field,geological structure,rockburst damage characteristics,thermal-force rockburst stress characteristics and excavation section surface of the Sanzhuling tunnel.The main research results are as follows:(1)The rock burst in the Sangzhuling tunnel occurs mainly in the middle of the tunnel to the exit section.The damage characteristics of minor,medium,and strong rockbursts are mainly reflected in the sound of cracking,the shape of the stripped rock,the shape of fractures and cavities,and the extent of the affected surface,all of which are enhanced with the increase in rockburst ratings.(2)The numerical simulation of the thermal rock burst section of the fourth section of the tunnel shows that the stress activity of the surrounding rock becomes intense during the on-site temperature range of the tunnel,and the possibility of rock burst increases,indicating that the temperature has strengthened the magnitude of the surrounding rock stress.Role,and increase the destruction of rock burst.(3)The main cause of high geothermal heat in the Sanzhuling tunnel is the active structure in the project area,geological structures such as regional fault zones,high heat flow background values in the area,and high thermal conductivity of the rocks distributed in the project area.Conduct heat.(4)The results of predecessors’hard rock macro test and PFC numerical simulation test under the action of heat-force are summarized.In general,within a certain range of values from 20°C to 40°C to 60°C,the strength indices and deformation indexes of hard rock characterization of rock mechanical properties are gradually increasing,and the characteristics of rockburst activity are becoming more pronounced.In the later temperature range,the mechanical properties of rock masses are gradually degraded,but the laws of different rock samples are somewhat different.(5)The absolute value of thermal damage D_T is used to characterize the influence of temperature on rockburst.Based on the case of rock burst in Sangzhuling tunnel,the empirical quantization table of temperature factor is given.At the same time,combined with the modified stress factor,the TRVI’rockburst proneness index of the hard rock tunnel under thermal-force interaction is obtained,and its empirical fitting relationship with rockburst failure depth is obtained:D_f=R(0.0004TRVI’-0.0126)Where D_f is the predicted depth of rock-burst destruction of thermal-force tunnel hard rock and R is the equivalent radius of the excavation section.And with the TRVI’value as the classification factor,the initial discriminant of rock burst intensity is given.