大柴旦盐湖采卤区地层剖面盐渍土基本类型及其抗剪强度试验研究

选取柴达木盆地大柴旦盐湖采卤区作为试验区,对区内地层剖面盐渍土的基本类型进行划分,即通过测定Na+、Mg2+、Cl-等易溶盐离子的方法,得出区内采卤区地层剖面盐渍土的主要类型是以亚氯盐渍土为主。在此基础上,对盐渍土进行扰动试样的室内直剪试验研究,以获取抗剪强度指标粘聚力c值与内摩擦角φ值。试验结果表明,该区盐渍土的含盐量由地表开始向下呈逐渐降低趋势,即由地表的6.89%降到地下4.5 m处的1.11%。粘聚力c值主要受试样含水量大小的影响,表现出随着含水量的增加,粘聚力c值呈降低现象,即当含水量由19.8%上升至23.3%时,粘聚力c值由35.4 k Pa下降至24.9 k Pa,下降率约为29.7%;而当含水量由23.3%下降至17.4%时,粘聚力c值则由24.9 k Pa上升至34.1 k Pa,上升率约为36.9%。内摩擦角φ值则受试样粒径影响相对较为明显,随着试样中粘粒含量的增多,粗粒含量相对减少,内摩擦角呈逐渐增大的趋势,即由24.1°上升至33.3°,增加率约为37.3%。随着试样中含盐量的增加,粘聚力c值和内摩擦角φ值均呈线性增加趋势。该研究成果将有助于进一步探讨含水量、颗粒大小以及含盐量对盐渍土试样抗剪强度变化的影响,且对区内盐田及其相应的基础设施建设有一定的理论指导意义。

The Experimental Research on Basic Types and Shear Strength of Saline Soil Taken from A Stratigraphic Section of Brine Mining Area in Da Qaidam Lake,Qaidam Basin

The testing site of this study is located in the brine mining area of Da Qaidam. The basic types of sa- hne soil taken from a stratigraphic section were analyzed via soluble salts content, and the ions such as Na ＋ , Mg2 ＋, and C1- were measured. The result shows chlomns saline soil is the main type of the saline soil in this tes- ting site. In order to obtain shear strength parameters of the saline soil samples, cohesion force（c） and internal friction angle （φ）, the disturbed saline soil samples were tested by direct shear test. The test results show that the salt content of the samples in the testing site dechnes gradually from the ground surface to lower parts of the stratigraphic section, that is to say, the salt content is 6.89% at the ground surface, 1.11% at the depth of 4.5 m beneath the ground surface. The cohesion force of the saline soil is mainly affected by soil moisture content. With soil moisture content increasing, the cohesion force of the saline soil dechnes. When the soil moisture content increases from 19. 8% to 23.3%, the cohesion force declines from 35.4 kPa to 24. 9 kPa, and the decrement ratio is 29.7%. The cohesion force increases from 24. 9 kPa to 34. 1 kPa, and the increment ratio is 36. 9% as the moisture content declines from 23.3% to 17.4%. The internal friction angle can be significantly affected by grain size as well, with the clay particle content increasing and the coarse granule declining relatively, the internal friction angle increases gradually from 24. 1% to 33.3%, and the increment ratio is 37.3%. With the salt content in the samples increasing, the cohesion force and the internal friction angle of the soil increase linearly. The achievements are conducive to make a further investigation into the influence of moisture content, particle size and salt content on the shear strength of saline soil samples, which is of instructive significance in the construction of salt field and the relating facilities in the area.