Field Testing and Centrifuge Modeling of Helical Piles in Sand

螺旋桩基础广泛应用于加拿大的建筑行业。与传统直桩相比，螺旋桩具有承载力大、可重复使用、安装快捷等优点；这些优点使得螺旋桩特别适用于加拿大的建筑业。近年来，加拿大的桩制造商开发了创新的螺旋桩类型，以满足日益增长的行业需求。RSP桩是一家总部位于阿尔伯塔省的公司，专门从事加拿大西部螺旋桩的制造、设计和安装。RSP已经确定了加拿大螺旋桩行业进一步发展需要解决的一些技术问题。首先，RSP桩的承载力-扭矩关联关系尚未建立。其次，螺旋板的最小厚度和焊接强度等力学设计与板上的土反压力有很大的关系，特别是在砂土中螺旋桩。建立切合实际的土反压力模型可以有效地改进螺旋板的机械设计，节约制造成本。三是通常要求桩公司对螺旋桩进行现场加载试验，但现场试验成本高，耗时长；此外，由于荷载或桩结构的复杂性，通常不可能进行现场测试，例如一组螺旋桩安装在承受弯矩和轴向载荷的砂土中。迫切需要一种更方便的螺旋桩测试方法，特别是在砂土中。阿尔伯塔大学（UAlberta）将与RSP合作，提供解决公司特定问题的技术解决方案。开展研究用螺旋桩的现场加载试验，开展超密砂土中小型螺旋桩的离心模型试验。通过这个为期3年的项目，阿尔伯塔大学和RSP将培养一名博士生和一名研究助理，他们最终将熟悉螺旋桩的行为。

Helical pile foundations are widely used in the construction industry across Canada. Helical piles have many advantages such as large capacities, reusability, and rapid installation, compared to conventional straight-shaft piles; these advantages make helical piles especially suitable for the construction industry of Canada. In recent years, innovative helical pile types have been developed by pile manufacturers of Canada to meet the increasing demand of the industry.RSP Piling is an Alberta-based company specializing in the manufacturing, design, and installation of helical piles across Western Canada. RSP has identified a few technical problems to be solved for the further growth of Canada's helical pile industry. Firstly, the capacity-torque correlations of RSP's piles have not been established. Secondly, the mechanical design of helical plate such as minimum thickness and the welding strength is significantly dependent on the soil reaction pressure on the plate, particularly for helical piles in sand. A realistic model of soil reaction pressure can effectively improve the mechanical design of the helical plates and saves the cost of manufacture. Third, piling companies are usually required to conduct field loading tests of helical piles, but the field tests are costly and time-consuming; in addition, it is often impossible to conduct a field test due to the complexity of loading or pile configuration, such as a group of helical piles installed in sand subjected to moment and axial loads. A more convenient test method of helical piles particularly in sand is strongly needed. The University of Alberta (UAlberta), by partnering with RSP, will provide the technical solutions to address the company-specific questions. We will conduct field loading tests of research helical piles and carry out centrifuge model tests of small-scale helical piles in very dense sand. Through the 3-year project, the UAlberta and RSP will train one PhD student and one research assistant who will eventually be familiar with the behaviour of helical piles.