Evaluation of the Collapse Potential Magnitude of Untreated and Treated Collapsible Gypseous Soil — A New Procedure

Many researches have been conducted to study the collapse potential of collapsible soils using collapse tests; single-oedometer tests, and double-oedometer tests. The radical rearranging of particles in response to a significant volume loss from wetting under loading is the definition of collapse. The main goal of this study is to create a method for recognition of gypseous soil that is susceptible to collapse. The suggested procedure depends on using a sample larger than that used in conventional collapse tests and the saturation of sample is done by flowing water from the bottom to the top of the sample. The new idea for the modified collapse test was made because of the limitations of conventional tests including the small size of sample that may not give a suitable collapse. In addition, the saturation process of the sample may not saturate all the particles. Also, the behavior of collapsible gypseous soil was investigated on soil improved with different Magnesium Oxide percentages (0, 5, 10, and 15%) and carbonated Magnesium Oxide with variable carbonation times (0, 1, 3, and 24 hours). The soil was prepared at two relative densities of 35 and 75 percent relative density. The collapse potential was investigated using a modified Rowe cell with soil moisture content sensors. The results illustrated that the size of the sample affects the collapsibility, the collapse potential increased from 15.8% to 22.3% and the collapse severity is changed from (severe trouble) to (very severe trouble) for the natural untreated gypseous soil using the conversional tests and modified test, respectively. The collapse potential increased by about 40% for the soil treated with different percentages of “Magnesium Oxide”. For the modified test, the collapse potential decreased by about 93% when using 10 percent of Magnesium Oxide then the sample was carbonated for 3 hours as compared with untreated soil.