黄土渗气系数原位测试原理方法及适用性试验研究

    EXPERIMENTAL STUDY ON PRINCIPLE, METHOD AND APPLICABILITY OF IN-SITU MEASUREMENT OF LOESS GAS PERMEABILITY COEF ̄FI ̄CIENT

    • 摘要: 渗透系数是黄土渗透变形破坏及黄土水理性质相关研究中的一项重要参数,而渗气系数与渗透系数具有良好的相关性且其测试过程不受黄土水敏性的影响,同时比渗透系数测定更为方便和快捷,因此具有良好的推广应用前景。本文介绍了黄土原位渗气测试方法的原理,在此基础上针对插入式和接触式两种原位渗气测试方法,在不同地区黄土地层开展了一系列原位渗气测试。试验结果发现两种方法对黄土地层的适用性有所不同,插入式方法十分适用于黏粒含量大于12.44%(塑性指数大于11.2)的黄土层,但对于黏粒含量低于12.44%(塑性指数小于11.2)的黄土层,插入式方法则会产生较大的误差。经综合对比认为,接触式方法由于人为误差小而普遍适用于黄土地层,但需要更大的工作面且更适于水平工作面,这对其测试速度和便捷性有一定影响。插入式方法所需工作面小,且同时适合水平和垂直工作面,因此更为方便快捷,但由于插入过程中探头对黄土层的扰动等人为因素的影响,因此更适合黏粒含量较高的黄土层。建议当黄土黏粒含量大于12.44%(塑性指数大于11.2)时,首选插入式方法,不满足此条件时再采用接触式方法。本文介绍的两种黄土原位渗气系数测定方法及其适用范围的确定为其在实践中进一步推广应用提供了理论基础。

       

      Abstract: The permeability coefficient is an important parameter in the study of loess seepage deformation and loess hydraulic properties. However,the gas permeability coefficient has a good correlation with the permeability coefficient,and water sensitivity of loess can not affect its testing process. At the same time,it is more convenient and faster than the determination of permeability coefficient. So it has a good prospect of popularization and application. This paper introduces the principle of loess in-situ gas permeability test method. On this basis,we carry a series of in-situ gas permeability tests in different loess areas by contact type and plug-in type. The test results show that the two methods have different application scopes for loess stratum. The plug-in method is more suitable when the clay content of loess is greater than 12.44%(the plasticity index is greater than 11.2). On the contrary,when the clay content is less than 12.44%(the plasticity index is less than 11.2),the plug-in method can cause larger errors. The comprehensive comparison shows the contact method is generally applicable to loess strata because of its less human error. But this method needs a larger working face and is more suitable for horizontal working face,which affects the test speed and convenience. The plug-in method needs a smaller working face,and is suitable for both horizontal and vertical working face. So it is more convenient and faster. However,the process of probe inserting into loess can cause disturbance,so this method is more suitable for loess layer with higher clay content. When the clay content of loess is greater than 12.44%(the plasticity index is greater than 11.2),we suggest to give priority to the plug-in method. If the site does not meet these conditions,we suggest to choose the contact method. The two determination methods of in-situ gas permeability coefficient of loess and their application scope provide a theoretical basis for further application in practice.

       

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