Settlement control and short supply of embankment filling are two technical problems influencing the construction and development of highspeed railway and highway, and the chances to solve these two problems may arise by applying geosynthetic to embankment engineering. It may be practical to treat the expansive soil (as filling of embankment) with geogrid, and it is hoped to control the (residual) settlement of embankment by using reinforcedmat with other methods in groundimprovement. Given that the aim of those two technical problems is the same, i.e. deformation controls, the key problem is how to gain the reasonable interaction parameters between geogrid and soil (IPBGS) through further investigation in the interaction mechanism between reinforcement and soil. Thus, in order to meet the deformation requirement in the application of reinforced techniques, this paper, based on extensive research of these subjects at home and abroad, systematically tests research (selection principle of testing methods, the steps of pullout tests and some relative criteria, and analysis method etc.) on IPBGS, corresponding tests (extension tests for geogrid and geotechnical properties tests of soil), and model tests of the performance of ground improvement with reinforced mat were carried out. Therefore, the main conclusions are as follows:1. Selection Principle of Testing Method for the IPBGS. Based on the state of the art research of IPBGS at home and abroad, the principal selection for testing the IPBGS is set up. The steps of pullout tests whose mode is strain control and some relative criteria are concluded.2. Analysis of IPBGS and its relative results by research. Based on the pullout tests data between geogrids and expansive soil/sands arranged by the orthogonal table L9 (34) , the following conclusions are reached:(1) The displacementproperties of pullout tests depend on the pullout speed. (2) Applying the method of ″process analysis″ to analyze pullout data, and with the concept of ″equiv
