Wandfrictie

Wandfrictie, or wall friction, is the frictional resistance that develops along the interface between a wall and the material in contact with it, most commonly soil against a vertical retaining wall. It acts parallel to the wall and works in conjunction with the normal contact pressure to resist shear movement of the soil relative to the wall. The strength of wandfrictie depends on the interfacial shear strength, which is modeled by an interfacial friction angle (often denoted delta) and the normal stress on the wall interface. This friction angle is influenced by factors such as wall roughness, surface treatment, the roughness of the soil grains, moisture content, compaction, and temperature.

Measurement and estimation: In geotechnical engineering, wandfrictie is typically assessed with interface shear tests, such as direct shear tests or specialized tests that measure shear strength along the wall-soil interface. In design practice, it is often estimated from laboratory data on soil-wall interfaces or from empirical values for common soil types.

Applications: Wall friction reduces lateral earth pressures on retaining walls and thereby affects stability and design of foundations, basement walls, tunnels, and pile caps. In analytical methods for earth pressure, the wall friction angle is incorporated to adjust the passive or active pressure on the wall.

Limitations: The value is not a universal material property; it is sensitive to boundary conditions and loading history. Scaling effects and long-term factors such as seepage or corrosion of the wall can alter wandfrictie over time.