基于离心模型试验的高强度桩复合地基桩间距效应分析

针对客运专线在软土和松软土地基处理中大规模采用高强度桩复合地基技术的应用情况,进行路堤荷载作用下不同桩间距的离心模型试验,分析桩间距的变化对高强度桩复合地基的荷载传递、破坏特点、桩土应力及垫层拉筋受力、地基沉降变形等工程特性的影响.试验数据表明:桩间距由3倍增至6倍桩径,高强度桩复合地基的沉降变形、桩土应力及比值、垫层拉筋受力等力学响应增大明显;随着桩间距的加大,高强度桩复合地基的桩顶和桩间土承受的应力均大幅提高,桩间距大于或等于5倍桩径后,桩顶垫层和桩间土先后达到极限状态,将产生显著的桩顶刺入变形和桩间土横向挤出变形,复合地基整体结构处于不稳定状态;垫层拉筋的受力沿横截面呈M形分布,峰值出现在两侧路肩附近位置的下方,与地基发生变形破坏的位置有较好的一致性.

Analysis on Pile Spacing Effect of Composite Foundation with High Strength Piles by Centrifugal Model Test

In view that the technology of composite foundation using high strength piles for treatment of soft soil and mollisol foundation of passenger dedicated lines has been applied widely in China,for handling the centrifugal model test of high-strength pile composite foundation is made under embankment loading and with different spaces between piles. The effect of pile spacing changes on features of construction works such as the load transfer,destruction features,pile and soil stress,geotextile reinforced cushion and settlement deformation of composite foundation using high strength piles is analyzed. The test results show that:① Once the space between piles increases by three to six times of the pile diameter,the mechanical responses such as the foundation settlement & deformation,pile and soil stress and force allocation of the reinforced cushion raise remarkably. ② Along with the space between piles stepping up,the stresses on pile top soil and soil between piles keep on increasing to a great extent. Once the space between piles increases by over five times of the pile diameter,the pile top cushion and soil between piles reach their limiting states,stab deformation of pile top and lateral extrusion deformation of soil between piles occur so that the general structure of the composite foundation turns into unstable status. ③ The geotextile reinforcement cushion is stressed on the horizontal cross-section in the form of the M shape,the peak value appears at the positions below two-side road shoulders,the same place of incurring of foundation destruction and deformation.