卸荷条件下黄土湿陷系数的计算方法及验证

自重湿陷性黄土场地桩间土在浸水作用下存在卸荷与湿陷的伴生过程,考虑卸荷作用的黄土湿陷变形还难以计算。首先探讨了卸荷湿陷与传统湿陷的差异性,分析了湿陷完成比、卸荷应力比等因素对黄土卸荷湿陷变形的影响,然后考虑各影响因素进行了卸荷湿陷试验,采用湿陷完成比、卸荷湿陷比和卸荷应力比来描述原状黄土的卸荷湿陷过程。由于逐级多次卸荷试验更符合工程实践中的连续卸荷工况,重点进行了多次卸荷试验。基于单次卸荷与多次卸荷试验结果,建立了考虑卸荷作用的湿陷系数计算方法。进一步采用卸荷湿陷系数,得到了考虑卸荷作用的自重湿陷性黄土场地桩间土自重湿陷量的计算方法,并通过室内验证试验与工程实例计算,论证了卸荷条件下黄土湿陷系数计算方法的合理性。

Method for calculating coefficient of collapsibility of loess under unloading

The concomitant process of unloading and collapse exists in the loess between piles of self-weight collapse loess site subjected to inundation. It is difficult to calculate the collapse deformation of loess under unloading. The difference between unloading collapse and traditional collapse is discussed firstly, and the effects of collapse completion ratio and unloading ratio on unloading collapse deformation of loess are analyzed. Then, the unloading collapse tests are carried out considering the above-mentioned factors. The unloading collapse process is described by the collapse completion ratio, unloading collapse ratio and unloading ratio. Because they are more in accordance with the continuous unloading conditions in engineering practice, the multiple-unloading tests are mainly carried out. Based on the results of single- and multiple-unloading tests, the method for calculating the coefficient of collapsibility considering unloading effect is established. Further, the method for calculating the self-weight loess between piles is obtained by using the coefficient of collapsibility under unloading. The rationality of the proposed method for unloading collapse is demonstrated through laboratory verification tests and project cases.