Silicate gels in civil engineering: The effect of organic matter content of soils on the hydraulic conductivity and strength of silicate gels

Abstract

Due to an increasing demand in space in urban areas, underground construction is becoming increasingly popular. To enable these constructions, silicate grout is injected to reduce the inflow of groundwater or to strengthen the soil. Unsuccessful grouting operations in the past have shown the need to investigate how environmental conditions affect grouting. This thesis focusses on how organic matter affects silicate grouting. Exploratory experiments were done focusing on three different aspects of the silicate grout, namely i) syneresis, ii) permeability and iii) Uniaxial compressive strength. Gel samples and grouted soil samples with increasing organic mass fractions were prepared and tested on these aspects. The syneresis experiments show that the shrinkage of silicate gels decreases with organic mass fraction. The syneresis experiments show that, in contrast to common belief, the permeability of grouted soils is not inherent to the grout, but rather to the imperfections in grouting procedures. The strength experiments show that an organic mass fraction of 8% may decrease the uniaxial compressive strength of grouted soil samples by up to 50%. In addition, the dehydration of grouted soil samples may also decrease the strength by 50%.