路堤坡脚被动正斜桩工程响应试验研究

Experimental Study on Engineering Response of Passive Positive Batter Pile at Embankment Slope Toe

被动正斜桩工程响应受到关注,为了解决坡脚处侧向约束桩可能向坡脚外倾斜,在路堤荷载作用下形成被动正斜桩的问题,在模型桩两侧对称粘贴应变片,使用双面胶黏贴土压力盒,通过PVC管设置百分表探针,设计杠杆加载装置,进行室内模型试验。对底端位置相同但向坡脚外倾斜0°,10°,20°的坡脚侧向约束桩进行研究。根据路堤填筑过程中的受力响应,获得坡脚正斜桩的弯矩、桩侧水平土压力和水平位移变化规律,为倾斜桩应用于软弱路基加固提供试验依据。结果表明:被动正斜桩桩身弯矩沿桩身自上而下先增大后减小再稍增大,峰值位置随倾斜度增大而略提高;加载侧水平土压力沿桩身自上而下先增大后减小再略增大,峰值位于桩长的0.3倍处;桩前土抗力沿桩身自上而下先增大后减小,峰值位于桩长的0.3倍处;直桩在荷载作用下以转动为主,稍有平移,正斜桩既平移也转动;p/p_(u)-y/y_(50)曲线平滑可以拟合;增加被动正斜桩倾斜角,其桩身弯矩、桩侧水平土压力、桩前土抗力、转动量减小,桩身平移量增大,桩自身越来越安全,但路基沉降增大,侧向约束作用降低。在实际工程中,为了发挥坡脚侧向约束桩的侧向约束效果,坡脚处侧向约束桩不宜设计为向坡脚外倾斜的正斜桩,并防止坡脚处侧向约束桩向坡脚外倾斜。

The engineering response of passive positive batter pile has attracted attentions.In order to solve the problem that the lateral restraint pile at slope toe may tilt out of the slope toe and form a passive positive batter pile under the action of embankment load,an indoor model test is conducted after pasting the strain gauges symmetrically on both sides of the model pile,pasting the earth pressure boxes with double-sided glue on both sides of the model pile,setting the dial gauge probe with PVC pipes and designing a lever loading device.The lateral restraint piles at slope toe with the same bottom positions and different inclines 0°,10ånd 20°outside the slope toe are studied.The variation rules of bending moment of positive batter pile at slope toe,horizontal earth pressure and horizontal displacement at the pile side are obtained according to the mechanical response during embankment filling,and provide experimental basis for the application of batter piles in soft roadbed reinforcement.The result shows that(1)the bending moment of the passive positive batter pile decreases after increasing,then increases slightly again along the pile body from top to bottom,and the peak position increases slightly with the increase of inclination;(2)the horizontal soil pressure on the loading side decreases after increasing,then increases slightly along the pile body from top to bottom,and the peak position is located at 0.3 times of the pile length;(3)the soil resistance in front of the pile decreases after increasing along the pile body from top to bottom,and the peak position is located at 0.3 times of the pile length;(4)the straight pile rotates mainly and translates slightly under the action of load,and the positive batter pile both translates and rotates;(5)the p/p_(u)-y/y_(50) curve is smooth and can be fitted;(6)with the increase of the inclination angle of the passive positive batter pile,the pile bending moment,pile side horizontal soil pressure,soil resistance in front of the pile and the amount of rotation decrease while the pile translation increases,and the pile itself gets safer,but the subsidence of roadbed increases,and the lateral restraint effect reduces.In the actual project,in order to exert the lateral restraint effect of lateral restraint pile at slope toe,the lateral restraint pile at slope toe should not be designed as the positive batter pile tilted outside the slope toe,and should be prevented from tilting outside the slope toe.