The present work deals with helical piles that extensively used in foundations for structures subjected to both compressive and tensile forces. The behavior of square helical piles models (5 × 5) mm, embedded in expansive soil overlaying a layer of well compacted sandy soil, (single and group of helical piles) were investigated and compared with ordinary piles. Model tests are performed with helical pile length 150, 200, and 300 mm and helix diameters 15 and 20 mm. Helical piles with one helix and double helix were considered. The pattern of helical piles group models consists of four piles in a square arrangement. Thirty-six models of helical pile groups embedded into the expansive soil were performed. It is found that the pile length, number of helix, and helix diameter have a great effect on the amount and rate of uplift movement of helical piles embedded in expansive soil. The deeper helical piles with higher L/D ratios showed greater pullout capacity comparing to the shallower piles. The maximum upward movement of helical piles group is less than that of single pile.

中文翻译：

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膨胀土中单根和一组螺旋桩的性能评估

本工作涉及螺旋桩，螺旋桩广泛用于承受压缩力和拉伸力的结构的地基中。对方形螺旋桩模型（5×5）mm的行为进行了研究，并将其嵌入膨胀土中，该膨胀土覆盖了一层密实的砂土（单个和一组螺旋桩），并与普通桩进行了比较。螺旋桩的长度分别为150、200和300毫米，螺旋直径为15和20毫米，进行模型测试。考虑具有一个螺旋和两个螺旋的螺旋堆。螺旋桩组模型的模式由四个正方形排列的桩组成。建立了膨胀土中埋设的螺旋桩群的三十六个模型。发现堆长，螺旋数，螺旋直径和直径对膨胀土中埋置的螺旋桩的上升运动的量和速度有很大的影响。与较高的L / D比的较深螺旋桩相比，较浅的桩表现出更大的拔出能力。螺旋桩组的最大向上运动小于单桩。