# Numerical Simulation of In-Situ Direct Shear Test and Damage Failure Mechanism Study of Concrete-Bedrock Cementation Surface

## TL;DR

This study uses simulations to understand how concrete and rock interfaces in dams behave under stress, revealing failure patterns and improving dam design.

## Contribution

A refined 3D simulation model for concrete-rock bonding interfaces is developed and validated with in-situ test data.

## Key findings

- Shear stress-shear displacement curves show peak strengths between 1.074 MPa and 2.073 MPa with 8.48% maximum error.
- Three failure modes are identified: bonding interface failure, mixed shear failure, and rock failure.
- Higher normal stress increases shear fracture area and smoothness along the bonding interface.

## Abstract

Owing to the insufficient understanding of the mechanical properties and damage mechanisms of concrete-rock bonding interfaces in dam foundations, this study establishes a refined three-dimensional simulation model for direct shear tests of concrete-rock bonding interfaces based on in-situ direct shear tests conducted at a reservoir. The damage evolution process and failure mechanisms of the concrete-rock interface under different loading conditions are investigated. The results indicate that under varying normal stresses, the shear stress-shear displacement curve exhibits an initial increase followed by a gradual decrease, with peak shear strength ranging from 1.074 MPa to 2.073 MPa and a maximum error of 8.48%, meeting engineering requirements. The damage evolution process of the concrete-rock interface under different normal forces was simulated and compared with in-situ direct shear test results, confirming the accuracy of the simulation. The failure modes of the concrete-rock interface under different loading conditions can be categorized into three types: bonding interface failure, mixed shear failure, and rock failure. The failure mode is closely related to the magnitude of normal stress—as normal stress increases, the area of shear fracture along the bonding interface expands, and the fracture surface becomes smoother. The findings provide a theoretical basis for the design, anti-sliding stability, and risk analysis of similar concrete gravity dams.