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顺德地区以强风化花岗片麻岩和强风化粉砂质泥岩为桩端持力层的预应力管桩,成桩一段时间内常出现静荷载试验异常沉降,复压管桩超送的现象,工程界对这一现象是否是桩端土软化引起争论不一.针对这一问题,在两个试验场设计不同桩尖的试验桩,利用静力触探、旁压试验、高应变测试、静载试验的原位技术检验压桩后一段时间内桩端土强度、水平应力与承载力的变化,结合室内试验结果系统评价预应力管桩桩端土是否会出现软化.研究表明,虽然顺德地区的强风化花岗片麻岩与粉砂质泥岩具有一定的遇水或扰动软化的潜势,但成桩后没有发现桩端土软化现象.以这两种地层作为桩端持力层的预应力管桩,桩尖是否开口,桩管是否采用混凝土封底,对预应力管桩的承载力影响不大.研究还指出,顺德地区残积土层具有明显的互层性,开展基础施工前重视勘察工作.本研究对于准确评价残积土地区的基桩承载力及保证工程质量具有重要意义.
In Shunde area, strong weathered granite gneiss and strong weathered silty mudstone are the prestressed pipe piles supporting the pile at pile end. During the pile-forming, abnormal settlement of static load test and superpipe transfer , The engineering community is controversial about whether this phenomenon is the softening of the pile-end soil.Aiming at this problem, different test piles with different pile tips are designed in two test sites, using static penetration test, pressure-side pressure test, Static test of in-situ technology to test pile end soil strength, horizontal stress and bearing capacity changes after a period of piling, combined with indoor test results to systematically evaluate the prestressed pipe pile tip soil will soften.The study shows that although Shunde The strong weathered granitic gneiss and silty mudstone in the area have the potential of water or disturbance softening, but no softening of pile-end soil is found after pile-forming. Prestressed pipe piles, pile tip is open, whether the use of concrete pipe pile cover, the bearing capacity of prestressed tubular piles little effect.Study also pointed out that the residual soil layer in Shunde has obvious inter-stratification, to carry out the foundation before the construction of emphasis Investigation work Study is important for an accurate assessment of residual bearing capacity and ensure the quality of the project land area of foundation piles.