Soil Spring Constants of Buried Pipelines for Seismic Design

This paper presents within the scope of the theory of static elasticity a derivation of soil spring constant in longitudinal direction of a buried pipeline in the seismic design. It is found that the spring constant depends on the shear modulus G of the soil deposits and the ratio of the radius of zero displacement over the radius of a buried pipeline structure. When increases, the soil spring constant decreases and the decreasing rate reduces remarkably when is greater than about 10. The ratio of soil spring constant over G is 2.7 when = 10. Furthermore, the dynamic effect of soil spring constants on buried pipeline structures is estimated analytically by the dynamic theory of elasticity. The soil spring constant that is derived, taking into account the boundary condition of ground surface, depends on the shear modulus G of the ground, nondimensional frequency b/Vs ( = circular frequency; b = radius of buried pipeline; Vs = ground shear-wave velocity) and nondimensional depth d/b (d = depth of pipeline).