Dynamic Behavior of Cemented Sand (Shear Modulus, Internal Damping, Grouting, Liquefaction).

Abstract

The investigation was conducted to provide fundamental knowledge of the dynamic behavior of cemented sand as a function of soil properties, cement properties and field conditions. The resonant column technique was used to determine the dynamic properties, shear modulus and internal damping, of cemented sand s with several types of cement: Portland cement type I, fly ash, lime and sodium silicate. The soils used in this research cover a range of effective grain sizes, 0.1 mm < D(,10) < 1.0 mm, and coefficients of uniformity, 1.0 < C(,u) < 4.5. Hypotheses based on the Wood equation and a visco-elastic model have been tested in this research. The time-dependent hardening process of cemented s and was also observed. All the test results lead to conclusion that the modulus ratio, defined as the shear modulus of s and before and after cementation, can be expressed in terms of coupling terms linking the properties of soil, D(,10) and C(,u), and the types of cement used. Two equations for estimating modulus ratio were developed based on the above mentioned hypotheses and experimental results. Well graded soil with small effective grain size can be significantly improved in shear modulus by cementing because of its greater number of contact points between soil particles. The shear modulus of sand can be increased by increasing the degree of cementation C%, expressed as a percentage of void space between soil particles being occupied by cement, and /or increasing the confining pressure. The effects of increasing the degree of cementation on shear modulus decrease as confining pressure increases. The limiting effect of confining pressure on cemented sand was postulated to provide the complete relationship between shear modulus, initial void ratio, confining pressure and degree of cementation of cemented s and . This concept is of great value in both theoretical research and practical applications of cemented sand from the viewpoint of increasing shear modulus. A hypothetical model consisting of visco-elastic elements, known as 3-parameter solid, was used successfully to predict observed test results for internal damping of cemented sand . This equation is also useful in studying the internal damping of cementitious composite materials which can be reasonably modeled by a 3-parameter solid. Test results also showed that both cemented sand s and hardened Portland cement concrete are cementitious composite materials and have similar fundamental mechanical properties.