Laboratory study effect of the width of the foundation, the relative density of sand and pressure on the settlement of strip footings

Determining the bearing capacity of the soil and its subsidence is one of the most important parameters that must be carefully evaluated when designing a safe foundation. In the present study, using a physical model, the behavior of the foundation located on sandy soil under static loading and the effect of various factors on soil behavior have been investigated. In this laboratory study, the effect of foundation width, sandy soil density and amount of overhead on strip foundation subsidence has been investigated. The soil material used in this study is poorly grained medium sand (SP). The foundation model has a width of 5, 7.5 and 10 cm and its length is 34 cm. The sand raining technique has been selected to obtain a homogeneous sample with a definite relative density and repeatability of laboratory conditions. The loading system is compressed air that has the ability to apply a uniform and static load. The relationship between the final relative settlement and the width of the foundations located on medium-density sandy soils is linear, and as the foundation width increases, the final relative settlement reaches less than its final ultimate bearing capacity. At the same pressure, the settlement of the foundation located on medium-density sandy soils is about 10 % higher than the foundation located on dense sandy soils. Soil behavior up to a pressure of about 50% of the final bearing capacity is linearly elastic. The pressure- settlement relationship of the strip foundation is linear up to about 5% of the foundation width. General shear failure occurs at a relative settlement of about 12 to 14%. For this reason, it is suggested to determine the ultimate bearing capacity of the strip foundation located on sandy soil, the amount of pressure such as 12% .