A simplified calculation method for upheaval deformation induced by unloading of silty clay foundation pit

Calculation of unloading-induced upheaval deformation of the foundation pit is of great significance to the stability analysis of the foundation pit. The exponential function between rebound modulus of soil and unloading ratio is deduced based on the existing laboratory test results of the soil compression rebound test and published results of silty clay foundation pits in different areas. Then, a simplified calculation method for upheaval deformation is proposed by combining the Mindlin's solution and the layer-by-layer summation method. The accuracy of the proposed method is validated using the results of two engineering examples. It is found that by using the simplified calculation method, the upheaval deformation induced by foundation pit unloading can be easily predicted only using soil parameters obtained by conventional geotechnical tests, and the predicted results of this method are close to the measured values. The further analysis shows that when the shape of the foundation pit is the same, the upheaval deformation at the bottom of the foundation pit nonlinearly increases with the linearly increase in the area of the foundation pit; when the area of the foundation pit is the same, the upheaval deformation of the strip foundation pit is smaller than that of the square foundation pit. The proposed method can provide theoretical guidance to the upheaval deformation prediction of the foundation pit in the silty clay area.