自平衡法在桩身竖向抗压承载力检测中的应用探讨

Discussion on the Application of Self-balanced Method in the Vertical Compressive Bearing Capacity Test of Pile

结合某钻孔灌注桩工程自平衡法检测桩身竖向抗压承载力应用实例,介绍自平衡法单桩静载荷检测试验原理,对依据规范进行检测和数据分析中遇到的问题进行探讨。自平衡点位置的确定是影响试验结果的关键,实际工程中可增加试桩数量,根据前桩试验情况对后桩平衡点位置进行及时调整,保证能够采用等效转换方式确定桩身极限承载力;依据规范进行等效转换计算时,在上段桩总位移小于下段桩总位移时,会存在某级荷载之后无法进行等效计算的情形;抗压摩阻力转换系数的选取对桩身抗压承载力计算结果影响较大,应结合勘察报告和当地经验合理取值,工程实际中可分别对不同抗压摩阻力转换系数给出不同极限承载力检值。

Combined with an application case of testing the vertical compressive bearing capacity of a bored pile by the self-balanced method,the principle of static load test of single pile by self-balancing method is introduced.The problems encountered in the testing and data analysis and processing according to the specifications are discussed.The determination of self-balancing position is the key to influence the test results.In practical engineering,the number of test piles can be increased,and the equilibrium position of back pile can be adjusted timely according to the test situation of front pile,so as to ensure that the ultimate bearing capacity of pile body can be determined by equivalent conversion method.When equivalent conversion calculation is carried out according to the code,when the total displacement of the upper pile is less than the total displacement of the lower pile,the equivalent calculation cannot be carried out after a certain level of load.The selection of the conversion coefficient of compressive friction resistance has a great impact on the calculation results of the compressive bearing capacity of the pile body,and it should be reasonably valued based on the investigation report and local experience.The different ultimate bearing capacity test values can be given for different conversion coefficients of compressive friction resistance in the engineering practice.