The use of chemical stabilization in Water Resource projects has increased considerably over the last 30 years. Chemical Stabilization in the form of Soil-Cement or Soil-Lime has been a main focus of the U.S. Bureau of Reclamation (USBR) in the construction of dams and other water resource applications.
The first use of Soil-Cement stabilization for slope protection was a test section constructed by USBR at Bonny reservoir in eastern Colorado in 1951. Observation of the performance of this test section for the first 10-year period of service indicated excellent performance of the stabilized section which was subject to harsh wave action and repeated cycles of freezing and thawing. This successful application lead to the conclusion that the use of chemical stabilization for slope protection, levee and dam cores, impervious liners, and maintenance accessibility was feasible based on both economical and service life considerations.
The key factor that accounts for a successful chemical stabilization project is careful predetermination of engineering control factors in the laboratory and implementation and verification of those results during construction.
The composition of soils varies considerably and these variations affect the manner in which the soils react when combined with a chemical stabilizer and water. The way a given soil reacts with stabilizer is determined by simple laboratory tests conducted on mixtures of stabilizer, soil, and water. These tests determine three fundamental performance requirements critical to water resource applications: strength, durability, and permeability. Strength as determined by unconfined compressive strength also determines the proper moisture content for compaction and hydration; and the density to which the stabilized soil must be compacted.
The decision to use soil stabilization instead of riprap for slope protection is primarily an economic one. The designer must compare the availability of suitable soil for soil stabilization versus the availability of suitable rock for riprap. The designer must prepare a cost analysis in arriving at a decision.
Factors that must be considered for chemical soil stabilization include cost of stabilizer, degree of suitable soil, special processing requirements, haul distance, dimensions and configuration of the slope protection and mixing and placement methods. For riprap, considerations include cost and availability of rock, size, haul distance, special processing requirements, configuration of placement and placement effort.