Experimental study on thermal-mechanical properties of energy pile in saturated clay foundation

Abstract

Based on the laboratory model test， the thermal-mechanical response of the energy pile in saturated clay foundation under multiple temperature cycles was studied. The temperature field around the pile， the settlement of pile and soil， the additional heating stress of pile and the shaft friction were analyzed. The results show that the temperature of pile and soil decreases along the depth and radial direction respectively， when the temperature rises. The settlement of pile top caused by cooling is greater than the expansion caused by heating. The heat transfer liquid was heated from 5 ℃ to 70 ℃， then maintained for 24 h， and then cooled to 5 ℃ for 5 h. This cycle for 3 times results in irreversible cumulative settlement of pile top. The settlement decreases with the distance from the pile， and the sedimentation rate of the soil decreases with the increase of the number of cycles. After three cycles， the settlement of soil surface 130 mm away from pile side reaches 1.42% of diameter of pile. The additional stress and the shaft friction of pile caused by temperature load increase gradually with the increase of temperature and number of cycles. The maximum additional heating stress reaches 695.40 kPa under working load， and the value varies with the change of pile top constraint condition， and its position moves gradually upward with the increase of the load on pile top. When heating， the negative shaft friction occurs in the upper part of the pile and the positive shaft friction occurs in the lower part. When cooling， the results are just the opposite. Under the action of the working load， the negative shaft friction area of the pile becomes smaller， and the zero-displacement point moves upward gradually. <fig fig-type="abstract-image" id="F1" orientation="portrait" position="float"><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="SP.J.1249-2022-39-1-85/9857FEDA-6661-4785-AADA-D5A71C0EB8A5-F001.jpg"/></fig>