深厚填土区微型钢管桩承载特性试验

为研究深厚填土区微型钢管桩承载特性及加固效果,通过室内试验和现场试验,测定微型钢管桩的应力-应变关系、各级荷载下的桩身轴力及桩顶位移,分析组合截面的弹性模量、钢管与水泥净浆分担的荷载比以及桩身轴力、桩侧摩阻力的传递变化规律.研究结果表明,钢管的套箍效应对组合截面弹性模量影响较小,实测值仅为不考虑套箍效应计算值的1.2倍;微型钢管桩中钢管分担的内力比较大,约占总内力的2/3;填土地区微型钢管桩Q-s曲线呈缓变型,端阻力分担的荷载基本趋于零,表现为摩擦桩的特性;微型钢管桩在填土地区具有较高的承载力,采用微型钢管桩对实际工程进行加固,目前最大沉降量满足规范规定的限值,表明微型钢管桩对深厚填土区地基的加固效果良好.

Experimental study on bearing characteristics of micro-steel-pipe pile in deep filling area

In order to study the bearing characteristics and the reinforcement effect of micro-steel-pipe pile in deep filling area, the stress-strain relationship of the micro-steel-pipe pile, the axial force of pile body and the displacement of pile top under various loads were measured by laboratory test and field test. The elastic modulus of composite section, the load ratio of steel pipe to cement paste, the transfer law of the pile’s axial force and lateral resistance were analyzed. The results show that the steel tube collar effect on the elastic modulus of composite section is small, the measured value is only 1.2 times of the calculated value without considering the collar effect, and the steel-pipe’s internal force in the micro-steel-pipe pile is relatively large, accounting for about 2/3 of the total internal force. The Q-s curve of micro-steel pipe pile is slowly deformed in filling area, and the load shared by end resistance tends to zero, which shows the characteristic of friction pile. The pile has high bearing capacity in the filling area. And the pile is used to reinforce the actual project, and the maximum settlement is up to the limit of the code, which indicates that the reinforcement effect of the micro-steel-pipe pile on the foundation in the deep filling area is fine.