基于虚拟嵌固点法计算钢管桩稳定性研究

Experiment study on steel tube piles stability based on virtual embedded solid point method

既有建筑物增设地下空间时,需要采用桩基础支撑上部结构,才能开挖建筑物下的土体。随着桩周土体的减少,钢管桩的稳定性会相应降低。利用虚拟嵌固点法提出了桩入土深度部分处于嵌固、未嵌固和半嵌固三种状态下受压计算长度公式。在模型箱内利用杠杆加载的方式进行了钢管桩的受压稳定承载力试验,分析了不同直径、外露长度的钢管桩在改变入土深度过程中稳定性的变化规律,结果表明:随着桩入土深度的增加,桩的稳定系数趋近一定值,该深度即为临界入土深度;桩的临界入土深度与外露长度无关,但与桩的刚度有关,刚度较大的桩,其临界入土深度也相应增加。比较虚拟嵌固点法、试验和JTS 167-4—2012《港口工程桩基规范》中规定方法得到的稳定系数可知,规范方法计算值明显偏低,虚拟嵌固点法计算值与试验值比较接近。

The underpinning pile can be used to support the existing building for construction of basement. The soil excavation around the pile can decrease the stability of steel tube piles. Based on virtual embedded solid point method,the formula for calculation length of compressed steel tube pile under the three states that the part of pile depth in soil is embedded,un-embedded,and half-embedded was put. In order to verify the reliability of the formula,the pile stability was tested in model box by pry bar loading device. The rules of steel tube pile stability with different diameters and exposed length were analyzed when the depths in solid are extended. Some conclusions are drawn as follows,with the pile depth in soil increased to the so called critical value of depth,the stability coefficient of pile reaches a certain value. The critical value of depth in solid has no relation with pile exposed length,but has relation with pile stiffness. The pile has the deeper critical value of depth in solid with higher stiffness. Comparing the stability coefficients of pile which are obtained from the virtual embedded solid point method,test data and method in code JTS167-4—2012,it is shown that the code method result is obviously lower,while the virtual embedded solid point method is close to the test result.