The selection of sealing technologies of the subsoil and hydrotechnical structures and quality assurance

Various types of trenchless methods are extensively used to create engineering barriers for the purpose of achieving relatively low hydraulic conductivity of the subsoil and hydrotechnical structures. The most commonly used technologies of the grouting curtain creating are the DSM (Deep Soil Mixing), WIPS (Vibro Injcted Thin Wall), low-pressure injection and jet-grouting. Vertical barriers are widely used in environmental control systems to restrict the lateral spreading of liquid or gaseous contaminants and for seepage control through and beneath a levees. The barrier walls are constructed in a single or two phases using a slurry composed mainly of bentonite, cementitious materials and water. Often to solve complex geotechnical problems the technologies are combined (e.g. combining DSM and jet grouting). In the paper some examples of practical application of chosen types of technology dedicated different problems solving are presented. The results of geotechnical investigations of hydraulic permeability, shear strength and depth control of cut-off wall are given. The tests were carried out using BAT system, Cone Penetration Tests (CPT) and drillings. The presented test results should help define the technical and financial criteria that should be used to compare grouting based methods and other techniques applicable to the same geotechnical special works. These recommendations should permit an adequate application of grouting techniques and contribute to finding solutions for the delicate problem of ground sealing, notably when proceeding with hydrotechnical or environmental structures placed below water table