| The thick landslide stratum(TLS)has the characteristics of poor soil uniformity and low stability,therefore large-scale landslides are prone to occur during soil excavation.Based on the actual treatment project of TLS slope at the entrance of the Makaozi Tunnel,this dissertation combines laboratory test and finite element simulation to analyze and compare the soil parameters and treatment measures that affect the stability of TLS.The related work and main conclusions include:(1)The indoor tests of soil properties in TLS were carried out.A series of targeted laboratory geotechnical tests were excuted based on the disturbed soil samples of the project.The results show that:a)the soil properties are silty clays with high liquid limit;b)the cohesion and internal friction angle of the soil decreases by 57.6%and 11.1%,respectively,when the water content increases from 25%to 40%.When water content approaches 40%,the cohesion index drops by more than 50%;c)the cohesion of the repeated direct shear test decreases with the increase of the shearing times,and tends to be stable after 5 times of repeated shearing.(2)The main causes of slope landslide in TLS were clarified.Based on the field engineering situation and laboratory test results,the simulation analysis was performed with the help of finite element analysis software ABAQUS to systematically analyze the influence of different factors on the slope stability.The results show that:a)higher water content,the lower slope safety factor(F_s);b)F_shas been improved to varying degrees by taking measures such as reducing the slope rate and adding support structures.(3)The effect of different treatment measures on improving the slope stability was systematically analyzed.A simulation test model is established based on the actual engineering data prototype,and the slope stability under different treatment schemes is compared and analyzed.The results show that:a)when the slope rate is reduced from 1:1.5 to1:1.8,F_sis increased by 44.6%(from 0.961 to 1.39),and the horizontal and vertical displacements are reduced by 67.3%and 49.2%,respectively;b)when anti-slip piles with a pile length of 20m and a cross-sectional area of 2.5m×2.5m are used for treatment at pile position 4,F_sis increased to 1.355,an increase of 40.9%,and the horizontal and vertical displacements are reduced by 91.6%and 84.8%;c)when using double-row steel pipe piles with a pile length of 18m for treatment,F_sincreases to 1.347,an increase of 40.1%,and the horizontal and vertical displacements are reduced by 31.9%and 31.7%;d)when the above-mentioned slope treatment measures are comprehensively adopted,F_sincreases to1.452,an increase of 51.1%;the horizontal displacement of the slope was reduced from348.3mm to 74.07mm,a reduction of 78.7%,and the vertical displacement was reduced from425.1mm to 92.6mm,a reduction of 78.2%.(4)Slope stability and safety status was evaluated through on site monitoring.According to the evaluation needs,the deep displacement and surface deformation monitoring were carried out.The results show that:a)the cumulative value of the observation section of the surface subsidence is 292.4mm and the maximum rate is-3.1mm/d.The total deformation measured after the treatment construction is 47.8mm and the maximum rate is 0.15mm/d;b)the maximum cumulative value of the horizontal displacement of the surface is 21.66mm,and the maximum rate is 0.65mm/d.The horizontal displacement measured after the treatment is3.56mm,and the maximum rate is 0.11mm/d;c)the maximum horizontal displacement before and after treatment are 8.83mm and 1.37mm,respectively.From the change law of monitoring indicators,the monitoring data of the slope all meets the requirements of stability control,40 days after the completion of the treatment construction. |
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