Laboratory devices

Pull-out box

The pull-out tests were carried out in relation to the standards recommendations ASTM D6706-01 (2007) and EN 00189016 (1998). This test allows determining the force to extract a geosynthetic sheet anchored inside soil and under vertical stresses.

The pull-out box (Figure 1) consists of a 1.10 meters wide, 1.10 meters depth and 2.00 meters long tank. The box can be closed and a flat can be inserted between the surface of the soil and the top of the box and inflated to apply the required stress.

The traction system is fixed onto the geosynthetic (geotextile or geogrid) with a metal clamp located in a guidance box inside the metallic tank (supposed to be rigid). The traction device was conceived specifically for this pull-out test. The idea was to build a system able to transmit the tensile force to the geosynthetic such as:

  • The pressure is as homogeneous as possible over the all width of the sheet,

  • There is no relative displacement of the reinforcement from the metallic clamp (no sliding).

The metallic clamp connects the reinforcement to the jack and distributes equally the tension efforts to the reinforcement. In order to avoid the effects of the front wall (roughness and stiffness), the reinforcement is placed at a certain distance (0.50 m) of it using a guidance box (0.50 × 0.70 × 0.16 m) located inside the tank. The metallic clamp is placed in this guidance box to prevent any contact with the soil that would lead to parasitic efforts.

The tensile force (applied on the 0.5 meter width geosynthetic sheet) and the displacements of the metallic clamp and the geosynthetic are monitored with displacement sensors during the pulling out test. In order to control the vertical stresses distribution, an earth pressure cell is set on the bottom of the tank underneath the sheet, between the guidance box and the back wall of the tank. The pressure applied inside flat is controlled with a manometer