Abstract: Current conventional primary thickness selection method of frozen wall is derived from the assumption of taking soil as a loose body, which is not applicable to clayey soil theoretically, hence the design of frozen wall thickness is always too conservative. As a result, it not only leads to a great waste of time and resources, but also causes many difficulties to the actual construction. In view of the above problems, based on the shear failure theory of clay stratum, this paper proposes and constructs a primary thickness selection method for the straight-wall arched frozen wall deeply buried in clay stratum. The rationality and applicability of the method are verified using numerical calculation and engineering application, and the superiority of the method proposed is further compared and analyzed in combination with the conventional design method. Research shows that: (1) Since the conventional design method cannot describe the failure mode of clay and calculate the supporting pressure of the frozen wall in an objectively and truly way, making it difficult to reasonably select the primary thickness of frozen wall. (2) Based on the shear failure theory of clay, this paper proposes and constructs a set of optimization methods suitable for the primary thickness selection of the straight-wall arched frozen wall deeply buried in clay stratum. It has been verified that the calculation result is effective and feasible as the primary selection plan. (3) Compared with the conventional method, the proposed method is theoretically closer to the engineering practice, and the frozen wall thickness obtained is obviously smaller than that calculated by the conventional method, which can effectively improve the economy of the artificial ground freezing construction on the premise of ensuring safety. (4) With the increases of cohesion and embedding depth, although the frozen wall thickness obtained by the proposed method shows a decreasing and increasing trend, respectively, they are significantly smaller than the design value of the conventional method under the same parameters. Besides, the increase of them has a positive correlation with the optimization of the frozen wall thickness. (5) The general formula and design process derived and constructed in this paper can provide necessary supplements to the existing specifications, and meanwhile, it could provide useful reference for both the design and construction phases when using the artificial ground freezing method in the similar projects in the future.

Key words: clay stratum, shear failure theory, straight-wall arched frozen wall, primary thickness selection method