2012 NGWA Ground Water Summit: Innovate and Integrate

Ground Movements and Ground Fracture Initiation from Groundwater Withdrawal and Recharge

Wednesday, May 9, 2012: 1:50 p.m.
Terrace Room D-F (Hyatt Regency Orange County)
Muniram Budhu, University of Arizona;
Ibrahim Bahadir Adiyaman, University of Arizona;
Rashidatu Ossai, University of Arizona;

The purpose of this contribution is to describe recent findings on ground movements and ground fracture from groundwater withdrawal and recharge from research conducted at the University of Arizona. The geology in many areas where groundwater is pumped or aquifer recharge and recovery facilities are located, consists of interbedded layers of geomaterials.  Analyses show that when the interbedded materials consist of layers of low and high hydraulic conductive materials, it is the low hydraulic conductive materials (LHCM) that control land subsidence and uplift.  These LHCM such as clays, silts and coarse-grained (sands and gravel) geomaterials control the groundwater flow paths, the amount, the spatial and temporal distributions of ground movements. An analysis based on the coupling of groundwater flow, soil deformation, soil stress states and soil failure shows that earth fissures would not develop if the subsidence gradient is less than 8 x 10-5 or Young’s modulus less than 200 kPa (equivalent to a shear wave velocity of 200 m/s) regardless of the pumping rate and the soil type.  This is an important finding for groundwater management because ground monitoring data from tools such as a radar mounted on a satellite can be used to forecast the potential development of earth fissures.  Earth fissures are more likely to be formed if the soil profile consists of a top layer of cemented soils.   However, the subsidence gradient at which earth fissures will form is lower for higher strength cemented top soil layer.  The subsidence gradient must be calculated over a characteristic length of Ö2 times the thickness of the aquifer.  Analytical and numerical results will be compared with field data from two study sites in Arizona.  One study site is located in a region where groundwater is pumped and the other study site is an aquifer storage and recovery facility.