| Recently large settlements of sewer pipes occurred at a job site in Flagstaff, Arizona, due to the intrusion of bedding materials into low strength subgrade. Field and laboratory tests showed that intrusion can be controlled simply by selecting the correct type of bedding material. Correlations were made between strength tests and intrusion. These correlations can be used to predict the stress on a subgrade at 1/4 and 1/2 inch of intrusion based on values of cone index or unconfined compressive strength. A computer model was utilized to predict cone index of a remolded subgrade silt under three different moisture density conditions, in a bin, with good success. The computer model was also utilized to estimate cone index of the subgrade under field conditions. |
