| In the process of expressway construction,slope instability and damage caused by excavation often occur,leading to construction stagnation and even loss of personal and property.At present,there has been a lot of research on slope excavation engineering,which has formed a relatively rich and perfect theoretical knowledge,but there are many factors that affect the stability of slopes and are very complicated.The impact of different conditions will also have The difference is that how to accurately analyze the deformation and failure mechanism of the slope and the stability during the excavation process and then carry out reasonable and effective prevention is the key problem faced by the construction of the expressway.Therefore,in this paper,the slope of DK0+100?EK0+420 section of Chengyi Expressway is taken as the research object.According to the actual geological conditions and deformation and failure of the slope,the deformation and failure mechanism,stability influencing factors of the slope and the stability during excavation are analyzed.According to the stability analysis,a reasonable and effective control plan is finally proposed to provide a reference for similar slope excavation projects.The main contents of the study are as follows:(1)Through the collection of regional geological data and field investigations,it was found that the slope has the characteristics of gently inclined bedding rock slope,the upper cover layer is mainly gravel containing silty clay,and the underlying bedrock is strongly weathered shale and medium differentiation Sandstone,where shale is broken under the influence of structure and weathering,coupled with the effect of long-term rainfall,a weak layer is formed between the contact surface of shale and sandstone.The weak layer is exposed due to excavation.Under the action of lateral support force,the slope slips and pulls along the plane.(2)Use the finite element strength reduction method to analyze the impact of different factors on the slope stability,determine the development trend of slope stability under various factors through the safety factor and the shear strain increment chart,and use MATLAB to fit the safety factor and the influencing factors Mathematical relationship.Then,the gray correlation method was used to analyze the sensitivity of each influencing factor,and it was found that the cohesion,internal friction angle and excavation platform were the most sensitive,and the rest were second.It shows that the main controlling factors affecting the stability of the slope are the shear strength of the rock itself and the width of the excavation platform.(3)The FLAC3 D software was used to simulate the distribution characteristics of the slope in natural state,step excavation and stress,strain and displacement under the action of rainfall,and to analyze the stability of the slope during the actual excavation process.The simulation results show that the excavation causes the slope stress field to be readjusted,the displacement increases significantly,and the shear strain increment gradually appears to penetrate.It has been completely penetrated,and the shear surface is displaced by the contact surface of the soft and hard rock layer,which shows that the slope is affected by excavation and rainfall.(4)From the analysis of the maximum unbalanced force monitoring data,it can be seen that as the excavation volume of the slope continues to increase,the unbalanced force of the slope body also gradually increases,and the unbalanced force reaches the maximum after the sixth step of excavation.However,after the fifth step of the excavation was completed,the maximum unbalanced force did not decay to zero due to the exposed surface of the soft and hard rock layers,indicating that the slope was already in an unstable state at this time.The maximum displacement is mainly concentrated in the third,fourth,and fifth grade slopes,which is consistent with the actual situation.According to the safety factor after each excavation,it can be seen that the stability of the slope does not always decrease,but shows a trend of rising first and then decreasing.After the excavation,the safety factor reaches the lowest under the influence of rainfall.(5)By analyzing the stability of the slope,it can be seen that the slope is currently in an unstable state.In order to prevent the slope from further deformation and destruction,an emergency treatment plan of backfilling and backpressure was adopted.In order to ensure the safety of the highway during normal operation,a comprehensive treatment plan of Qingfang + anti-slide pile + slope protection + interception of drainage ditch + back edge crack backfill was proposed,and the stability of the treated slope was analyzed using FLAC3 D It meets the requirements of highway slope stability,shows that the treatment plan is reasonable and effective,and also achieves the purpose of this study. |
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