基于温控直剪装置温度变化对土体力学特性影响试验研究

Experimental Study on Influence of Temperature Change on Mechanical Properties of Soil Based on Temperature-Controlled Direct Shear Device

为研究土体物理力学性质随温度变化规律,通过改进的大型温控直剪设备——FAST-1型,在准确控制温度变化且施加较大法向压力条件下,对西藏高原冻土区采集的土体重新制备并在不同温度下(15℃、5℃、-5℃、-15℃)进行直剪试验。剪切过程中测量土体的温度、抗剪强度、剪胀量、黏聚力和内摩擦角。试验结果表明:温度的改变可以使粉质黏土的力学性质产生较大的改变,负温条件下土体抗剪强度随着温度的降低而增加,正温条件下土体抗剪强度基本保持不变;负温条件下黏聚力在-15℃最高可达1.8 MPa,约为正温条件下土体黏聚力的900倍。内摩擦角呈现出两端温度变化大,中间温度变化小的趋势。由于温度对黏聚力和内摩擦角的影响,在负温条件下,剪切过程中剪切面比较粗糙造成土体的剪胀明显较大,最大可达2.5 mm,约是正温条件下的5倍。

In order to study the laws of the change of soil mechanical properties with temperature,the soil collected in the frozen soil area of the Tibet Plateau was re-prepared and subjected to different temperatures(15℃,5℃,-5℃,-15℃)for direct shear test through an improved large-scale temperature-controlled direct shear equipment-FAST-1 under the condition of accurately controlling temperature changes and applying a large normal pressure.The temperature,shear strength,dilatancy effect,cohesion and internal friction angle were tested in the process of shearing.The test results show that the mechanical properties of silty clay can be changed greatly with the change of temperature.The shear strength of silty clay increases with the decrease of temperature under negative temperature condition,while the shear strength of silty clay remains almost unchanged under positive temperature condition.The maximum cohesion of silty clay under negative temperature is 1.8 MPa at-15℃,which is about 900 times of that under positive temperature.The internal friction angle shows a tendency of large change at both ends temperature and small change in the middle temperature.Due to the influence of temperature on cohesion and internal friction angle,the dilatancy of soil under negative temperature is obviously larger than positive temperature,up to 2.5 mm,which is about 5 times of that under positive temperature.