An experimental and numerical study of the moisture effects on soil strength and performance of adobe walls

Adobe structures represent a significant part of the architectural heritage of the world, including the southwestern United States. In New Mexico, moisture damage from capillary rise of ground water or rain is a major cause of structural weakness and collapse of adobe buildings. In addition, adobe structures are susceptible to lateral loading, such as those from earthquakes. This research studied the effects of moisture on the soil strength and the performance of adobe walls.;An adobe soil composed of silty clayey sand was used to make adobe bricks from which soil specimens were trimmed. Consolidated, drained direct shear tests were performed on saturated specimens to find the effective cohesion (c') and effective friction angle (&phis;'). Unconfined compression tests and unconsolidated, undrained direct shear tests were conducted on specimens with different water contents. The compressive strength and shear strength of the adobe soil were found to decrease when water content increased. The filter paper method was applied to construct the soil water characteristic curve (SWCC). The unsaturated shear strength of the adobe soil was predicted using the SWCC data and c' and &phis;'. The failure envelopes in the shear strength-matric suction plane were found to be nonlinear and their initial slope was close to &phis;', and decreased as the suction increased.;An approach was proposed to consider the effects of moisture in the adobe walls using finite element analysis (FEA). The input parameters for the material constitutive model as functions of water content were determined from the experimental work. The changes in material properties according to the target water content were implemented in the FEA input file by adding syntax to define the moisture conditions in the wall as a field variable. A parametric study was conducted to determine the effects of moisture on the adobe wall's ability to resist in-plane and out-of-plane lateral loading. The variables considered were the water content, and the height (H) and length ( L) of the moist section in the wall. The numerical modelling results showed the weakening effects on the walls as the water content increased and as the moist area increased in length and height in the wall.