Abstract：The study takes the two-anchor system of EBTP (Extension Type Bamboo/Rebar Tension-Pressure Anchor Rod) anchors in earthen sites as the research object. Indoor two-anchor DIC (Digital Image Correlation) pullout tests with anchor spacing of 0.3m and 0.6m are conducted to clarify the load-displacement relationship and typical failure modes. First, based on the characteristics of anchor slip failure mode, a 2D FEM (Finite Element Method) simulation method for the two-anchor system is proposed. The simulation of contact pairs and nonlinear springs is then employed to the pressurised section slurry/soil interface and rod/pulp interface in tension. It is found that, at a 0.3m spacing, the primary failure mode involves horizontal cracking along the rammed earth layer. While at 0.6m spacing, a conical cracking pattern emerges with a transition between tension and compression at an angle of 30~45°, yielding a maximum crack radius of soil top is approximately 24cm. The bearing capacity decreases by approximately 7% at 0.3m spacing compared to 0.6m. The simulation analysis illustrates that anchor spacing has a significant influence on the group anchor effect. For one thing, when the spacing exceeds 0.6m, the group anchor effect is more limited, which is consistent with experimental results. For another, the depth of the expansion body demonstrates an approximately linear correlation with the ultimate bearing capacity of the anchor. Therefore, as anchor length increases, the bearing capacity initially increases sharply, followed by a more moderate increase. The experimental results indicate the group anchor effect gradually strengthens. Yet the increment in bearing capacity due to increased anchor length outweighs the loss caused by the group anchor effect. These findings provide valuable insights for the design of EBTP anchor groups in earthen sites. The simulation methodology in this study can be used to predict and optimize the anchorage design parameters in the design of anchoring works at earthen sites.
2024, Vol. 45 
