2.4.1. Fixing System

The test pile fixing system was mainly constructed by connecting the high-strength bolt embedded in the rigid foundation (the rigid foundation was mainly made of in-situ cast concrete and steel bars) with the steel support, which was used to fix the test pile to simulate the anchored section of the actual cantilever anti-slide pile. The steel support was welded by channel steel, angle steel, and steel plate, and its grade was Q235. The fixed part of the test pile was the pile groove formed by channel steel. Considering the dimensional error in the pouring process of the test piles, the size of the pile groove should be slightly larger than the section size of the test piles to facilitate the placement of the test piles, the size of the pile groove was designed as 105 mm × 155 mm, and the thickness of the pile groove was 10 mm. The stiffening rib plate was welded on the side of pile groove and the inclined supports (6 mm thick, mainly made of angle steel) were set at the four corners of the bottom plate to stabilize the pile groove. A rectangular working platform (top plate) was installed on the top of the pile groove, and its dimensions and thickness were 455 mm × 305 mm and 6 mm, respectively. The dimensions of the bottom plate were 750 mm × 500 mm, and its thickness was 10 mm. In order to ensure the stability of the steel support, the pre-embedded bolt component was set at the front and rear sides of the bottom plate of the steel support, which were anchored with the rigid foundation, and then the pile groove transmitted the thrust load to the pre-embedded bolt through the stiffened rib plate and inclined support to obtain the reaction force. The pre-embedded bolts adopted M20 bolts (matched with flat washer and nut), and the embedded length was about 230 mm. The three-dimensional concept diagram of the test pile fixing system is illustrated in Figure 6.

**Figure 6.** Three-dimensional model diagram of the fixing system of test pile.
