Engineering and Construction

Besides ground surface subsidence, the extraction of groundwater or oil can also cause the opening of ground fissures. For example, there has been up to about 5 ft (1.5 m) of ground surface subsidence in Las Vegas valley between 1963 and 1987 due primarily to groundwater extraction. It has been stated that the subsidence has been focused on preexisting geologic faults, which serve as points of weakness for ground movement (Purkey et al., 1994). Figures 7.17 to 7.21 show five views of damage caused by ground fissures at a housing development in Las Vegas, Nevada, as follows:

1. Figure 7.17. This photograph shows an open ground fissure. In many cases the ground fissures have an upper soil plug that hides the presence of the fissure. Water from irrigation or leaky pipes can soften the soil plug and cause the fissure to open at ground surface.

2. Figures 7.18 and 7.19. These two photographs show foundation damage. The house structure was so badly damaged that it was demolished and the only remaining part is the foundation. In Fig. 7.18, the fissure can be seen running directly underneath the foundation.

3. Figures 7.20 and 7.21. These last two photographs show damage to the roads and sidewalks.

The houses adjacent the roads were badly damaged and demolished. Although the fissures are not exposed at ground surface, the settlement of the street and sidewalk caused by the underground fissures are clearly evident in these photographs.

Ground fissures can also be caused by other geologic mechanisms. For example, strike-slip fault rupture can create open fissures at ground surface. Another possibility is landslide movement, where fissures may open up at the crown, flanks, or main body of the slide.