Interfacial shear failure and peak strength analysis of geomembrane and polyester filament geotextile
Homembrane, geotextile and other geosynthetic materials are widely used in the fields of environmental protection, transportation, water conservancy, agriculture and building waterproof.
Due to the weak shear strength between the interfaces, the slope slip stability of geosynthetic-containing materials is often determined by the shear strength between them. The following geomembrane for GM, rough geomembrane for GMT, smooth geomembrane for GMS, polyester filament geotextile for GT.
The roughness of the geomembrane surface largely affects the peak shear strength of the interface with the geotextile. According to the shear test of GM / GT interface, the peak shear strength of GMT / GT is significantly higher than that of GMS / GT, and the horizontal shift corresponding to the peak stress is also large.
The damage forms of geosynthetic material interface include: non-woven fabric surface fiber is pulled out or torn, and GMT surface rough surface bulge is damaged or smoothed in the interface shear process, in addition, the form of interface failure is affected by different factors, including: normal load, rough surface forming process and rough surface bulge distribution. The influence of the spacing of the rough surface is two aspects.
Generally, the smaller the spacing of the rough surface, the greater the shear strength of the interface. However, when the spacing of the rough surface exceeds a certain degree of tightness, which is too compact, it will make the GMT surface become uniform and smooth. The effect of the rough surface convex will be significantly reduced, and the interface shear strength will also be reduced.
Figure 1 shows the sample comparison of two flat rough masks with different convex spacing.
In order to understand the relationship between GM and GT interface disruption and quantify the interface, comparative experiments under different conditions were conducted using direct shear instrument.
The experimental data reduces and simulate the interface between GMT, GMS and GT of different gram weight specifications in the process of engineering application, which is conducive to the selection of GM, GT and other geosynthetic materials in different engineering application environments.
Table 1 and Table 2 below show the mechanical properties indexes of 1.5 mm GMS and 1.5 mm GMT, and the polyester filament textile is 100g, 300g, 400g and 600g.
For GM / GT interface shear test, the normal stress used after installation selects 50,100,200,300 and 400 kpa, and the interface shear test rate is 1.0mm / min. Interfacial shear stress-horizontal displacement relationship between 1.5 mm GMS and 300gGT:
As shown in Figure 4, at the beginning of shear, the shear stress increases rapidly with the horizontal displacement to the peak, and the horizontal displacement corresponding to the peak of shear strength is 2~3mm. Subsequently, the shear stress decreases at a rapid rate and tends to stabilize.
With the increase of the normal load, the phenomenon of strain softening is more obvious. No GMS and GT surface after shear test.
As shown in Figure 5, at the beginning of shear, the shear stress rapidly increases along with the horizontal displacement to the peak, and the peak horizontal displacement corresponding to the shear strength is 4~5mm, then the shear stress slowly decreases to the residual strength with the horizontal displacement, the same rule as GMS / GT, with the increase of normal load, the strain softening is more obvious.
After the test, the fibers on the GT surface were damaged, with no obvious damage to the GMT surface.
As shown in Figure 6, ignoring the cohesive component which has little influence on the interface shear strength of geosynthetic materials, the peak shear intensity of GMT / GT under different normal loads was fitted to obtain the modified geosynthetic material boundary shear friction angle. Table 3 shows the shear friction angles of different geosynthetic interfaces, and the GMS / GMT interface, with the peak friction angles reduced by 10.1 compared to the GMT / GT interface.
Table 3 Geosynthetic interface shear friction angle
| Interface type | Peak friction angle |
| GMS/GT | 15.1° |
| GMT/GT | 25.2° |
Table 4 shows the interface shear peak friction angle obtained from the shear test between 1.5mm GMT and GT of different specifications.
Interface type | Peak friction angle |
GMT/GT(100g) | 25.4° |
GMT/GT(300g) | 25.2° |
GMT/GT(400g) | 27.1° |