Injection Technologies for Elimination of Karst-Suffosion Hazard and Soil Subsidence in the Foundation of Buildings and Structures

It is shown that the installation of cutoff walls (CW) using various drilling and injection technologies should be considered as the most effective method to protect against the development of karst-suffosion hazard during construction and operation of transportation and other structures. Depending on geotechnical and hydrogeological conditions at the future construction site, it is possible to use various mixtures based on polymers, liquid glass, etc., for CW construction and elimination of karst unconsolidation. It is shown that polymeric impregnation compositions are effective for the accelerated option of increasing the bearing capacity of soils, and the use of compositions based on liquid glass allows to increase biologic resistance. The use of jet grouting technology, collar technology or their combination is also effective. It is reasonable to use mineral-based special injection mixtures for compaction and hardening of karst rocks. These mineral-based special injection mixtures are more technologically advanced, and the soil cement of CW and compacted karst rocks is more durable compared to soil compacted with polymer-based or liquid glass injection mixtures. An effective injection mixture for CW installation for protection against karst-suffosion hazard is the “PFS+” injection mixture, which should be considered as an alternative to injection mixtures based on bentonite, polymers or liquid glass. Taking into account the high probability of sulfate corrosion development during injection of fractured gypsum rocks, the efficiency of application of mineral fine-dispersed binder - “Introcem” slag based microcement in collar technology - is shown. In order to eliminate karst unconsolidation, the most preferable approach is the use of the “ZIS” special injection mixture, which is made on the basis of mineral composite binder. The experience of using the “Super-Jet” technology under different geotechnical conditions and design solutions has shown that the strength of the soil cement body formed by this technology can reach 15 MPa, and the cutoff walls are fully waterproof. It is shown that higher strength of soil bases is achieved when they are injected with powder-activated compositions.