Abstract: Fifty four pull-out tests between geogrid and expansive soil, sand designed by orthogonal table L9(34) were performed, the variable rules of friction parameter between reinforcements and soils (FPBRS) defined by different criterion have been given, as well as the affecting degree of factors influencing on FPBRS. And in accordance with concept of ‘equivalent pull-out displacement’ presented and the performance of FPBRS, the whole process of pull-out tests were divided into two parts and three stages, with which the FPBRS could be reasonably gained in various displacements states, thus it’s possible to gain the FPBRS both in limit state and working stress conditions.

Key words: parameters between reinforcements and soils, affecting factors, affecting degree, pull-out tests, process separation and analysis.