Stress-strain State of Foundation Soil during Injection of Cement-sand Mortar in Hydrofracturing

Abstract

   The relevance of the study  is due to the need to improve the efficiency and quality of the injection process of cement-sand mortar during foundation soil strengthening.    The use of a check valve and a clamping device allows achieving more uniform and stable filling of voids and cavities in the ground. Modern conditions of construction and reconstruction of facilities place increased demands on technologies for foundation soil strengthening, especially weak soils, where injection methods show insufficient effectiveness. Geotechnical monitoring based on computational software systems help to assess the stress-strain state of soil during injection. The applied approach allows not only to increase the injection efficiency but also to provide a more precise prediction of the soil behavior after strengthening, which is especially important in building design and operation.    Purpose:  The purpose of this work is to improve and commercially test injection of cement-sand mortar during foundation soil strengthening, including the use of a check valve and a clamping device.    Research findings:  It is shown that the stress-strain state of soil grows after strengthening. Calculated and real deformation of foundations decreases by 12 times, and stresses in the soil increase from 450 to 850 kN/m 2 . The change in the pumping pressure of the mortar over time confirm its dependence on physical and mechanical properties of soil, which made it possible to more accurately regulate the injection process. Soil creep affects the stress-strain state of the foundation soil during injection of the reinforcing mortar and requires special attention when strengthening the foundation soil of buildings. It is important to note that stress relaxation after injection depends only on the pressure and physical and mechanical properties of the soil and is V = const.