Estimating UCS of cement-grouted sand using characteristics of sand and UCS of pure grout

For quality control and the economical design of grouted sand, the prior establishment of the unconfined compressive strength (UCS) estimating formula is very important. This study aims to develop an empirical UCS estimating formula for grouted sand based on the physical properties of sands and the UCS of cured pure grout. Four sands with varying particle sizes were grouted with both microfine cement and Ordinary Portland cement. Grouted specimens were prepared at three different relative densities and at three different water-to-cement ratios, and unconfined compression tests were performed. The results demonstrate that UCS of grouted sand can be expressed as the power function of the UCS of cured pure grout: UCSgrouted sand / 1 MPa = Asoil x (UCSpure / 1 MPa)N. Because the exponent N strongly depends on the combination of pore area and pore size, N is expressed as the function of porosity (n) and specific surface (Sa). Additionally, because Sa determines the area of the sand particle that cement particles can adsorb and n determines the number of cementation bondings between sand particles, Asoil is also expressed as the function of n and Sa. Finally, the direct relationship between Asoil and N is also investigated.