Experimental study on the anti-jacking-up performance of a screw pile for photovoltaic stents in a seasonal frozen region

The soils in seasonal frozen regions freeze and thaw frequently, causing severe frost heave and thaw settlement problems, which bring challenges to piles of photovoltaic stents. In this paper, laboratory tests are conducted with different types of screw piles under freezing conditions, with also using smooth piles for contrast. The aim is to simulate the freezing process of screw piles according to practical working conditions based on the similarity principle. Internal thermal resistance is ignored. The change laws of temperature, displacement, as well as the influence factors of types of screw piles are analyzed. The results indicate that: with a freezing depth of 30 cm, which is half of the pile length, large-double-bladed screw piles perform the best in antijacking-up, while all-bladed screw piles perform the worst, independent of the types of soil samples tested. The fitting relationship between jacking-up displacement and freezing depth is also proposed for each type of pile. Results obtained can provide an important reference to site construction in seasonal frozen regions.概要目 的基于相似性原理,模拟实际工况中的降温冻结过程;通过室内试验确定最优桩型,并推导冻拔量与冻深的定量关系。创新点进行季节性冻土区螺旋桩的自由冻胀试验;2. 根据相似性原理,在室内试验过程中调整冷端温度与几何尺寸以缩短冻结时间;3. 推导得到6 种桩型冻拔量与冻结深度的定量关系。方 法1. 通过相似性原理确定试验条件,模拟实际工况中的降温冻结过程;2. 观测此过程中5 种螺旋桩型的温度场、冻拔量和土压力随时间的变化规律,并设置一组光滑桩作为对比;3. 根据冻拔量大小选取最优桩型,并推导冻拔量与冻深的定量关系。结 论1. 螺旋桩冻拔量小于光滑桩,验证了螺旋桩抗冻拔的有效性;采用不同土样有相同规律。2. 冻深达到0.9 m 的季冻区,双螺旋大叶片桩抗冻拔效果最好;螺旋叶片建议设置在非冻区;冻拔量大小关系为:双螺旋大叶片桩