Method for measuring pile displacement and internal force caused by soil expansion of expansive soil foundation

The present invention aims to provide a method for measuring the pile displacement and internal force caused by soil expansion of an expansive soil foundation so as to rapidly and accurately determine the internal force and displacement of a pile foundation caused by by expansion of expansive soil. According to the method, the sizes of the pile foundation and the expansive soil and material parameters are measured; according to the measured parameters, the equivalent spring stiffness of non-expansive soil on the lower layer and pile end soil is calculated, and a spring acts on the cross section of the pile at the bottom of the expansive soil; a differential control equation of the pile displacement within the scope of the expansive soil is acquired; and a displacement function is subjected to Taylor expansion, and according to a pile top boundary condition and a spring boundary condition on the cross section of the pile at the bottom of the expansive soil, a computational formula for solving the pile displacement and internal force caused by soil expansion of the expansive soil foundation is acquired. With the adoption of the method, the up-dragging force and up-dragging displacement of the pile caused by the expansive soil under the expansion condition are accurately calculated through less calculation.