This paper presents a pipe-soil interaction model for sand soils capable of predicting the development of pipe penetration into the soil and the associated soil resistance that may be mobilized against horizontal pipe motions. The model is based on dimensional analysis and development of appropriate empirical equations which are fitted to large-scale laboratory data from several sources. The development of penetration is described by considering the work done by the pipe on the soil. For a given penetration, the force-displacement curve is described. The model has been used to predict time histories of penetration and horizontal pipe displacement from large-scale laboratory tests where pipe sections were subjected to forces representative of those from irregular waves and currents. A good reproduction of the time development of both penetration and displacement is given over the whole range of relevant hydrodynamic and soil parameters.