Earth fissure formation from groundwater pumping and the influence of a stiff upper cemented layer

Typical soil profiles in arid and semi-arid regions where groundwater is pumped consist of geological materials that vary from uncemented soils to rock. A finite-element analysis using a 20 m thick stiff cemented top layer over a 400 m thick aquifer is used to study how the cemented layer affects earth fissure initiation. This paper presents the results of this study on the key parameters influencing earth fissure formation in a soil profile with a top cemented layer. Three scenarios, each representing three cementation strength parameters, are investigated. A method based on the gradient of the slope of the subsidence bowl is proposed to determine earth fissure initiation. It is shown that earth fissures will not form for gradients below 8 × 10 −5 . The gradient at which an earth fissure would form depends on the cementation strength and tensile strength of the upper cemented alluvium layer. A highly cemented upper alluvium layer is more prone to earth fissure formation than an uncemented one. However, if the top layer is stiff enough to be classified as a ‘rock’, it will be less prone to earth fissure initiation when the cementation increases.