Analysis of Non-Yielding Basement Wall Adjacent to Strip Footing

Abstract

Foundation depth below the ground surface is one of the major factors that contributes to the bearing capacity and settlement of shallow foundation. Hence, it is common to find adjacent buildings on shallow foundations that are constructed at different depths. This situation leads to geotechnical and/or structural problems especially when a shallow foundation is constructed adjacent to a basement wall. A literature review and communications with local municipalities indicated that there is no solid code of practice that can be adopted to solve problems of shallow foundations constructed adjacent to non-yielding wall. The objective of this research is to study the behavior of non-yielding walls adjacent to strip footing experimentally and analytically. Parameters investigated during this study are footing depth below ground surface, horizontal distance from the basement wall to the footing, footing contact pressure, and width. To achieve these objectives, 15 reduced-scale wall-footing model tests with 1.15 m height by 1.4 m width and 2.7 m in length were constructed with well graded backfill sand. The strip footing was subjected to an incremental vertical stress until excessive deformation occurred. The wall-footing models were instrumented to measure lateral wall deflection, footing vertical stresses and settlement, horizontal forces transferred to the top and bottom boundaries of the wall, and vertical force transferred to the bottom of the non-yielding wall. Results showed that the non-yielding wall and the adjacent strip footing are working interactively, and the load capacity of the strip footing was affected significantly by the behavior of the non-yielding wall. Location of the footing relative to the wall, the footing width, and the footing embedment depth were the major parameters that influenced the wall-footing responses. The existence of the strip footing in the vicinity of the basement wall imposed significant vertical and horizontal forces at the wall top and bottom boundaries. A comparison between experimental results and results from the elastic theory method in combination with Jacky formula for lateral earth pressure at rest indicated that the analytical method underestimated the lateral earth forces on non-yielding walls due to strip footing. Therefore, a modification of the current used analytical methods was suggested to improve its accuracy. Finally, the experimental and analytical results indicated that the location of lateral forces above the wall bottom boundary was changed with the footing design parameters.