自平衡测试法在广东地区的推广及应用研究

Research on the Promotion and Application of Self-balanced Loading Test in Guangdong Province

自平衡测试法具有场地适应性强、简便、高效、安全等优点,广东地区深基坑多、工期紧、试桩吨位大,自平衡测试法在广东地区得到了充分的发展和应用。本文通过详细介绍几个典型工程实例,简要归纳了自平衡测试法在广东地区基桩竖向抗压/抗拔静载试验、桩底持力层岩基载荷试验、深层平板载荷试验的应用情况,通过对比分析,得到了如下结论:荷载箱的合理设计直接影响到试验桩荷载箱处的桩身混凝土浇捣质量;成孔时间过长、泥皮过厚、抗拔系数取值过高都有可能导致灌注桩的上部摩阻力实测值低于理论计算值;应控制拔管时机和速度并按规范要求进行有效清孔;确定抗拔系数时,务必结合地方经验或试验桩的现场试验结果进行取值。

The self-balanced loading test method has the advantages of strong field adaptability,simplicity,high efficiency and safety.Due to the large number of deep foundation pits,tight construction period and large tonnage of test piles in Guangdong,the self-balanced loading test method has been fully developed and applied in Guangdong.Several typical engineering examples of the self-balanced loading test method were introduced in detail,the application of this method in vertical compression/withdrawal static load test on piles,rock foundation load test on pile bottom bearing layer,deep plate loading test were briefly summarized,and the following conclusions were obtained through comparative analysis:The pile body concrete at the test pile load box is directly affected by the rational design of the load box.All excessively long hole-forming time,excessively thick mud skin,and excessively high pull-out coefficient may cause the actual measured value of the upper friction resistance of the cast-in-place pile to be lower than the theoretical calculated value.The extubation time and extubation speed should be controlled,and effective hole cleaning should be performed according to the specifications.When determining the pull-out coefficient,it is necessary to take values based on local experience or the field test results of the test pile.