黄土液化试验中反压饱和技术的改进与应用

Improvement and application of backpressure saturation method in loess liquefaction test

动三轴试验是评价场地地震液化势的有效手段之一,而饱和是确保动三轴试验结果可靠性的首要步骤。常规的反压饱和法是利用外界的大反压力将水强行压入土中,压缩土中的空气,从而使试样饱和的方法;利用该法饱和可有效的提高土样的饱和度和饱和效率。黄土属于特殊土类,现行的动三轴试验方法都是沿用砂土或粉土的试验方法,然而由于黄土具有特殊的结构性,利用施加大反压的方法饱和黄土时会对其结构产生破坏,因此通过常规的反压饱和方法饱和黄土时存在较大的局限性。本文结合黄土的特性,探讨了常规反压饱和方法在黄土饱和时存在的主要局限性,考虑黄土的性质,结合既有的黄土脱气水位循环差饱和技术对常规反压饱和方法进行了改进,并在WF-12440型动三轴扭剪仪上通过液化试验检验了改进后的反压饱和技术在黄土液化试验中的应用效果。结果表明:改进后的反压饱和技术综合了常规反压饱和法和脱气水位循环差饱和技术的优点,使黄土在饱和过程中结构不产生破坏的条件下短时间内达到较高的饱和度,有效地提高了试验效率;该方法适合在黄土液化试验中广泛应用。

The dynamic triaxial test is one of the most effective technologies to evaluate the seismic liquefaction po- tential of engineering site, and saturation is the most important step to ensure that the test is successful. The mech- anism of the conventional backpressure saturation method is what press water into the samples with an outside pres- sure, and it can enhance the saturation level of samples and efficiency of the test. However, the loess is one of the particular soil, the dynamic triaxial test methods of the soft followed the methods of the sand or silt, hence the con- ventional baekpressure saturation method should possibly break the micro-strcuture of the loess. In this paper, based on interpretation of the principle of the conventional backpressure saturation method, the limitation of it in dynamic triaxial test of loess is discussed by combining with the structural and water sensibility of the loess. And the saturation method was improved by considering the properties of the loess and the successful saturated methods of the loess which was used before. Moreover, the validity of the after-improved method was verified by using the liquefaction test results of Lanzhou loess. The results show that, the after-improved backpressure synthesizes the merit of the water-head saturation method and the backpressure saturated method, el and efficiency was improved, and it suits the loess liquefaction test. saturation method the saturation lev-