Study of Grouting in the Hydraulically Activated Subfoundation Soils Using the Comprehensive Approach

Introduction. The large-scale “wet” closure of collieries had led to irreversible changes in the underworked rock mass. First of all, there took place the mine-water level rise and hydraulic activation of buildings’ subfoundation soils, which induced the new geodynamic effects and hazardous deformations of buildings. Therefore, it is necessary to carry out the reconstruction of buildings’ subfoundations on the underworked territories. Under these circumstances, the high-pressure jet grouting with viscoplastic grouts using the hydraulic fracturing is considered a highly-promising trend of soil grouting. The work aims at studying the parameters of grouting and the degree of consolidation of hydraulically activated soils on the underworked territories.

Materials and Methods. The research was carried out with the rock full scale specimens, taking into account their physical-mechanical and strain-strength properties. The comprehensive approach to research implied studying the geotechnical conditions and the technological parameters of rock grouting along with the quality of stabilisation and waterproofing of hydraulically activated soils.

Results. In accordance with the comprehensive research methodology, at the first stage, the geotechnical and miningengineering analysis of the underworked territories were carried out and the geostructural typification of the ShakhtinskNesvetaevsky district territories was substantiated depending on the thickness of the covering deposits. At the second stage, the grout pad formation parameters at contact with the parent rocks were analytically determined. Moreover, for dispersive decompacted rocks the consistent patterns and the degree of filtration consolidation were established in the empirically-analytical way by viscoplastic grout injection. Using the computer and physical modeling method, the consistent patterns of subfoundation soils deformation before and after grouting were obtained for three geostructural types. At the third stage, the field studies of the grouting parameters and quality were carried out during the subfoundations reconstruction of two buildings in the city of Shakhty. It was proved that grouting in the hydraulically activated soils increases their strength up to 0.4 MPa and reduces subfoundations deformation by 2–2.5 times.

Discussion and Conclusions. Application of the comprehensive methodology to the study of grouting in the hydraulically activated soils of the underworked territories made it possible to substantiate the process flow schemes and parameters of consolidation and waterproofing of dispersive and fractured hard rocks. Based on the analytical, computer, laboratory and field study results, the consistent patterns and the degree of variation in the deformation-strength properties of the hydraulically activated subfoundation soils after viscoplastic grouting were established.

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