不同酸碱条件下黏性土的热力学稳定性试验研究

AN EXPERIMENTAL STUDY ON THE THERMODYNAMIC STABILITY OF CLAYEY SOILS WITH VARIOUS ACIDITIES AND ALKALINITIES

在常温(-4℃～60℃)条件下,以广西南宁市河流相沉积土为研究对象,制作三轴扰动样(d=39.1mm,h=80mm)并将其抽气饱和、浸泡在不同pH值溶液中360h,然后取出风干至浸泡前的含水量,最后分别静置于10℃、30℃、40℃、50℃、60℃的温度环境中168h及在40℃环境中静置48h,120h,168h,240h,360h后进行三轴试验,探讨热作用对不同pH值粘性土热力学特性的影响.通过室内试验得出了不同pH值土样的峰值应力差(σ1-σ3)、粘聚力c及内摩擦角ψ随温度t的变化规律.结果表明,相对中性土样来说,当化学溶液的pH＜7(酸性)和pH＞7(碱性)时,热侵蚀效应强度增大,当环境温度t=40℃时,酸性(pH=2)和碱性(pH=12)重塑土样的粘聚力c均最小,分别为62.9kPa和80.5kPa;在40℃环境中热作用168h后,酸性土样的粘聚力c有最小值,酸性和碱性土样的粘聚力c均小于未浸泡土样,碱性土样的内摩擦角ψ为最小.因此,不同pH值环境对土体热力学特性的影响是不同的,而且化学溶液酸性越强或碱性越强对土体强度的热影响越大,所以,不同酸碱度是影响土体热力学稳定性的主要因素之一.

The river deposit in Nanning, Guangxi was made into three-axle disturbed samples （ d = 39.1ram, h = 80ram） at usual temperatures （ -4℃ ～ 60℃ ）. The samples were saturated and soaked in different pH value solutions for 360 hours and, taken out and air-dried to the water content before soaking. The samples were then placed in five types of temperature environments separately （10℃, 30℃, 40℃, 50℃, 60℃） for 168 hours, and three-axle tests were conducted after 48 hours, 120 hours, 168 hours, 240 hours, 360 hours in a 40℃ environment. The purpose of the experiment is to examine the influence of various heat functions on the characteristics of the structural thermodynamics of the clayey soils and to obtain the peak stress difference, cohesion （c） and intrinsic friction angle （φ） with various temperatures and pH-values. The result of the experiment indicates that the cohesions at acidity （pH = 2） and alkalinity （pH = 12） are at minimum, 62.9kPa and 80.SkPa, respectively, when the environmental temperature is 40℃, and when the pH-value of chemical solution is smaller than 7 or greater than 7, the heat erosion effect increases. Affected by heat in the 40℃ environment after 168 hours, the cohesion of the acid sample is minimum, the intrinsic friction angle （φ） of the alkaline sample is also minimum, and the cohesion values of beth the acid and the alkaline samples are smaller than those of the unsoaked samples. Different pH-value conditions influence the thermodynamic characteristics of the clayed soil differently and, the higher the acidity or alkalinity of the chemical solution, the more thermodynamic influence on the intensity of the clayey soil. Therefore, acidity or alkalinity is one of the main factors influencing the thermodynamic stability of clayey soils.