Stability Problems of Collapsing Soil

Where collapsing soils exist in extensive areas of canal construction, stabilizing the foundation subsoils by ponding method is necessary before embankments and linings are built. As these soils a may still be somewhat critical after collapse, slope stability analyses must include this hazard In interpretation of soil strengths and safety factors. A procedure is presented for delineating collapsible soils and includes settlement records from 16 miles of preconstruction ponding treatment on the San Luis Canal, California, substantiating the criteria. Soil strength values from laboratory tests, which considered the critical nature of such soils, were used in a stability study. Safety factors were adjusted to account for earthquake stresses, and consideration was given to reduced ultimate strength and limits of strain to resist bulging and cracking of the lining. Improved stability was attained by zoning the canal embankments and compacting foundation surfaces with extra heavy pneumatic rollers.