基于相对湿度场和变模量本构的岩土膨胀分析模型

Analysis Model of Geotechnical Materials Based on Relative Humidity Field and Variable Modulus Constitutive Model

随着含水率(湿度)的增加,红层黏土(岩)会表现出体积膨胀和吸水软化的双重特征,这是诱发红层滑坡和路基隆起等地质灾害的主要原因。为研究含水率对受荷岩土体变形的影响,本文在湿度应力理论的基础上,对含水率归一化处理,提出基于相对湿度的变模量本构,建立岩土膨胀分析模型;以固结黏土和红层黏土岩为研究对象,开展膨胀和吸水软化试验。结果表明:膨胀试验中,黏土岩和固结土的侧限膨胀率分别为0.345和0.205,膨胀应力分别为225.0和112.5 kPa,黏土岩具有更强的膨胀能力;固结土吸水效率更高,能够更快地达到膨胀平衡状态。软化试验中,干燥状态下黏土岩的压缩模量较大,但吸水过程中模量的衰减也较快,饱和状态下固结土与黏土岩的压缩模量基本相同。基于试验数据,对本文模型的稳态参数进行反演,并基于已标定的分析模型对侧限膨胀试验进行模拟,一方面,验证本文方法在稳态分析时的适用性;另一方面,给出了相对湿度场平均扩散率K的标定方法。以圆形洞室遇水问题为算例,进行了稳态理论计算和瞬态数值计算,以说明本文模型在应用于岩土膨胀大变形分析时的优越性。本文分析模型参数易获得,数值模拟结果准确性高,可为红层膨胀岩和膨胀土地区工程建设提供理论指导。

With the increase of water content(humidity),red bed clay(rock)shows the characteristics of volume expansion and water-softening simultaneously,which is the main reason for geological hazards,such as landslides and subgrade uplifts in red bed regions.To understand the in-fluence of water content on the deformation regulation of loaded geo-materials,a water-softening model based on relative humidity(normalized water content)was proposed and a corresponding expansive analysis model was established.Firstly,taking consolidated clay and red bed clay rock as research objects,expansion,and water-softening tests were carried out to calibrate the steady parameters of the model.The expansive tests show that the confining expansion rate of clay rock and consolidated soil are 0.345 and 0.205,and the expansion stress is 225.0 kPa and 112.5 kPa respectively,which reflected that the clay rock has a stronger expansion capacity than the consolidated clay.Meanwhile,the test also shows that the consolidated soil absorbs water more quickly and can reach the expansion equilibrium state faster.The water-softening test shows that the compression modulus of clay rock is larger than consolidated clay in the dry state,and the decrease of compression modulus with water content isalso faster.The compression modulus of consolidated clay and clay rock is basically the same in the saturated state.Then,the confining expan-sion test was numerically simulated based on the calibrated analysis model,and the applicability of the method in terms of steady analysis was verified.Meanwhile,the average diffusivity K(which is a transient parameter)was calibrated by the comparison of tests and numerical results.Fi-nally,taking the problem of circular cavern encountering water as an example,the steady theoretical analysis and the transient numerical calcula-tion were carried out to illustrate the superiority of the model in expansive large deformation conditions.In summary,the parameters of the novel model are easy to obtain,and the numerical result is accord with tests,which can guide the engineering practice in the red bed expansive clay or swelling rock areas.