| In railway construction and operation and maintenance,the safety of cutting slope has always been the focus of railway engineering due to the influence of natural environment such as rain and snow,engineering geology,hydrogeology and operating load.Bolt support is one of the railway slope protection methods,with ideal protection performance and low cost.Based on the super-deep cutting project of Longzhen to Heihe section of Bei’an-Heihe Railway,the DK217 + 180 slope is selected as the analysis section.After calculation,the safety factor of the slope in the natural state is 1.07,and the rock mass at the foot of the slope has a tendency to slip toward the railway direction due to the penetration of the shear strain area inside the slope body,which does not meet the stability requirements of the ’ Code for Design of Railway Earth Structure ’(TB 10001-2016)for the cutting slope,so reinforcement treatment is needed.The influence factors of cutting slope stability are discussed by using Lizheng geotechnical software and FLAC 3D software respectively.The influence of soil mechanical parameters cohesion,internal friction angle,bolt length and bolt inclination angle on slope safety factor is analyzed:(1)The slope safety factor is positively correlated with the cohesion of rock and soil.With the increase of soil cohesion,the maximum shear strain increment gradually develops to the toe of the first grade slope,and the development area gradually decreases.(2)The internal friction angle has a very obvious effect on the safety factor of the slope.Increasing the internal friction angle of the rock and soil can also meet the requirements of slope stability without supporting measures.(3)The longer the anchor rod,the greater the safety factor of the slope,the higher the slope stability,but the safety factor growth rate is small,the length of the anchor rod increased from8 m to 18 m,only increased by 0.04;(4)When the dip angle of anchor bolt is 15 °,the safety factor of slope is the largest.With the increase of dip angle of anchor bolt,the safety factor of slope decreases gradually.Based on the above conclusions and the actual morphological characteristics of the slope,the anchor support scheme is designed to reinforce the slope,as follows:The first,third,fifth and seventh grade slope,each grade slope is arranged three rows of bolts,each row is arranged four bolts,the horizontal distance of bolts along the slope is 2.0m,the vertical distance is 1.5m,the length of bolts is 8m,it is full-field anchoring bolt,the dip angle of bolts is 35°;For the second,fourth and sixth grade slopes,3 rows of anchor bolts are arranged in each slope,4 rows of anchor bolts are arranged in each row,the horizontal distance of anchor bolts along the slope is 2.0m,the vertical distance is 1.5m,the length of anchor bolts is 20 m,the length of anchorage section is 10 m,the length of free section is 10 m,and the incident angle of anchor bolts is 20°;In the eighth slope,three rows of bolts are arranged,and two bolts are set in each row.The horizontal distance of the bolts along the slope surface is 2.0 m,the vertical distance is 1.5 m,and the length of the bolts is 8 m.It is a full-field anchoring bolt with the dip angle of 35 °.Through the numerical simulation of FLAC 3D software,the safety factor of the slope after support is 1.32,which meets the stability requirements of the ’ Code for Design of Railway Earth Structure ’(TB 10001-2016)for the first-level permanent slope,indicating that the bolt support scheme designed in this paper can effectively improve the stability of the slope.The research results of this paper can provide reference for the study of bolt reinforcement of super deep cutting slope in railway engineering,and enrich the application of bolt support in railway engineering. |
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