EVALUATION OF DEFORMATION PARAMETERS OF SILO FOUNDATIONS REINFORCED WITH SOIL-CEMENT ELEMENTS

Abstract

The mandatory controlled criterion for steel silos is the limitation of foundation settlement and tilting, which is regulated by DBN V.2.6-221:2021. The threshold value of silo settlement is Smax,u = 150 mm. The most economical foundation solution is a large-sized slab on a natural base or a soil cushion. It is possible to stabilise the weak base by reinforcing it with vertical soil-cement elements (SCE). In Ukraine, most foundations have an underground gallery or silo floor. When the silos are first loaded, there is geodetic monitoring of the vertical settlement of the silo base and comparison of its data with the threshold values of settlement and tilting. The objective is to investigate the effect of limited-depth soil reinforcement on the stabilisation of the soil base and the average total foundation settlement. The task of the study is to create a methodology for predicting the impact of reinforcement with soil-cement elements on the parameters of the soil base general stiffness for a silo foundation. The research methods are geodetic monitoring of settlements around the perimeter of silo foundations during initial loading at four different elevators with different geological conditions. Thus, the predicting method of the impact while reinforcing with soil-cement elements on the general stiffness parameters of the soil base for the silo foundation was tested on the bases of silos for four elevators. These elevators represent different engineering and geological conditions. The proof of the methodology’s validity is the coincidence with the results of geodetic subsidence monitoring along the perimeter of silo foundations. According to the research results, it is possible to state that the reinforcement of the foundation base with vertical soil-cement elements allows for the effective stabilisation of soil parameters. We propose an evaluation method of the reinforcement effect with soil-cement elements in the form of the stabilisation coefficient for the soil base, kEi. We further prove the primary role of the soil-cement reinforcing elements operation and their length while stabilising the base. The base stiffness is stabilised at the compressible stratum depth and beyond the foundation boundaries. It is possible to use the method of reinforcement influence evaluation to determine the actual parameters of the stabilised soil base, n, according to geodetic monitoring data. The authors have studied the effect of limited depth reinforcement for stabilising the foundation. The research obtained the empirical dependence of the reinforcement required depth at given depth values for the base compressible layer. The authors proposed using the linearly deformed layer method, considering the operation of soil-cement elements as discrete soil reinforcement. The numerous experiments with the Finite Element Method confirm the high convergence of the calculated results with those obtained analytically. Keywords: foundation settlement, soil-cement element, geodetic monitoring, steel silo, foundation stiffness.