黄土地区微型钢管水泥桩单桩承载特性试验研究

随着桩基技术的不断发展,微型钢管水泥桩在工程中的应用越来越广泛;黄土地区对微型钢管水泥桩的研究相当匮乏。为了研究黄土地基中微型钢管水泥桩的承载特性、桩身轴力的传递特征、桩侧阻力和端阻力的发挥性状,对兰州地区3根微型钢管水泥桩进行现场单桩静载试验。在3根试验桩桩身埋设混凝土应变计,对试验桩进行内力测试。研究结果表明:(1)微型钢管水泥桩桩周土经水泥浆加固过后,单桩承载力提高较大,该类微型钢管水泥桩桩基设计时可适当提高侧阻取值。(2)微型钢管水泥桩桩端附近存在桩侧摩阻力的弱化效应。为了增大桩侧摩阻力的发挥,可以考虑桩端做扩大头,进而增加桩基承载力。(3)当桩顶荷载与桩顶加载极限值比值小于等于0.615时,桩顶沉降主要为桩身压缩变形引起,规范简化法综合系数取值0.2可近似计算桩顶沉降,且误差较小。当桩顶荷载与桩顶加载极限值比值大于0.615时,计算桩顶沉降时还应考虑桩端土体的沉降。

Experimental study on bearing capacity of single pile with micro steel pipe cement pile in Loess Area

With the development of pile foundation technology, the application of micro-tube concrete pile in engineering is more and more extensive, and the research on micro steel pipe cement pile is quite scarce in loess area. In order to study the bearing capacity, the axial force transfer law of pile body, the lateral resistance and the end resistance of the micro steel pipe-cement pile, it makes static test for the three micro steel pipe-cement pile.Concrete strain gauges are respectively buried in the axis of the 3 test piles to test the internal force of the test piles. The results show that(1)The surrounding soil of the mini steel pipe cement pile is strengthened by cement slurry. The bearing capacity of single pile has been greatly improved. When designing the pile foundation of this kind of project, the value of lateral resistance can be increased properly.(2)There is a weakening effect of side friction on the side of the concrete filled steel tubular pile. It is possible to consider the end of the pile as the enlarged head, so as to increase the resistance of the pile side and increase the bearing capacity of the pile foundation.(3)When the pile top load and pile top load limit ratio is less than or equal to 0.615,pile top settlement is mainly caused by compression deformation of pile body. When the pile top load and pile top load limit ratio is greater than 0.615, the calculation of pile settlement should also consider the settlement of pile end soil.(4)When the pile top load and pile top load limit ratio is less than or equal to 0.615, the main reason of pile top settlement is the compression deformation of pile body. The 0.2 value of the composite coefficient of the simplified method can be used to calculate the settlement of the pile top and the error is small.