Research on calculation method of slip fixture parameters of slope anchor cable compensation tensioning equipment based on contact mechanics

This paper addresses the technical problem that prestressed anchor cables on highway slopes often become too short during operation due to steel strand reservation and the failure of traditional compensation tensioning equipment. To solve this issue, a contact mechanics‑based calculation method for slip fixture parameters is proposed. The approach converts the three‑dimensional frictional contact problem into a plane strain problem by equating the discrete slip teeth to an infinite contact body. A friction contact model is developed using Hertz contact theory to predict the total tensile force of the fixture. A yield strength model is established using the Johnson stress solution and the Von Mises yield criterion to assess the yield risk and safety factor of the slip teeth. Systematic parametric numerical analysis is performed to reveal the influence of key geometric factors (slip center distance, contact length, curvature radius) on tension concentration and contact stress. The method is then applied to design a slip clamp for a four‑beam anchor cable on a Guangdong roadway, using 45CrNi alloy steel, and a field compensation tension test is conducted. The field test successfully achieved a tension of 600 kN. The plastic “tooth marks“ and the bearing capacity formed on the anchoring surface agreed well with the theoretical predictions. The close agreement between experimental outcomes and theoretical calculations demonstrates the reliability and engineering practicability of the proposed method. This study provides a systematic solution—from theory to practice—for the core fixture design of compensation tensioning equipment.