| The construction of highway on soft soil layer is more prone to slip,collapse and other safety accidents,so it is necessary to adopt reinforcement method to treat the soft foundation before construction to improve the bearing capacity of the weak foundation and enhance the overall stability of the foundation.In this paper,several soft foundation sections of Yunnan QiShi highway line were selected,and the theoretical derivation,analytical calculation and finite element calculation were used to comprehensively analyze the damage mechanism of gravel pile composite foundation and the cause of roadbed slip,and the principle and design method of joint reinforcement of gravel pile composite foundation-reinforced concrete pile at the foot of slope were studied,and further combined with the tilted pile results obtained from the indoor model test,the tilted pile reinforcement was designed and optimized relevant parameters of soft foundation.The main conclusions are as follows:(1)For a number of sections of highway slippage,the foot of the slope level launched and side soil arching and other problems,the establishment of complex soil layer under the roadbed model,combined with the project site slippage found:the lower part of the right foot of the slope contains soft plastic-like organic soil tip extinguisher exacerbated the right side of the roadbed strain and settlement,relying only on gravel piles can not effectively resist soil shear displacement,reinforcing the local uneven soft foundation should be carefully considered,take gravel pile composite foundation to improve the bearing capacity of soft soil,should be appropriate to increase the rigid pile arrangement,improve the roadbed shear resistance,to prevent the occurrence of overall or local shear damage.(2)The deformation and force characteristics of the vertical rigid pile were obtained through the analytical solution of theoretical analysis and numerical simulation analysis method,the lateral shift of the foot of the slope is reduced from 1.212m to 0.123m of the composite foundation of gravel,and the stability safety factor is increased from 0.96 to 1.44,the effect of additional rigid anti-slip pile at the foot of the slope on the embankment soil slip damage limitation is more obvious;the pile displacement is significantly larger than the theoretical value,while the pile bending moment value is small,and the pile body shows the overall movement with the lateral movement of the soil body.(3)The force deformation characteristics of passively loaded piles under different pile inclination angles(0°,10° and 20°)and pile bottom embedded solidity(20°)were analyzed by indoor model test.The pile horizontal displacement,pile bending moment and soil pressure distribution rules were analyzed,and it was determined that 20° inclination angle is the suitable pile angle with the smallest value of horizontal pile bottom displacement and the best pile bending resistance.Enhancing the degree of embedded solidity at the bottom of the pile can significantly reduce the horizontal displacement at the top of the pile,which can more effectively enhance the soil body’s ability to resist slip damage and improve the overall stability of the soil body.(4)In the numerical analysis software ABAQUS,a three-dimensional soft ground+inclined pile reinforcement numerical model was established to study the deformation characteristics of embankment slope and the change law of pile displacement and bending moment under five pile lengths and three pile spacing of 2B,3B and 4B(B=2.5m)when the pile angle is 20°.The pile inclination reduces the pile load section and increases the pile embedded section,which relatively increases the anti-slip pile embedded effect.The batter pile reinforcement effect is better than vertical pile.In this project,when the soft foundation is treated with inclined pile reinforcement,it is recommended to use 20° inclined pile with 17.5m pile length and 2B pile spacing. |
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