Modeling Rate Effects and Cyclic Loads With the Pressuremeter

Abstract

A relatively new tool, the cone pressuremeter (CPMT), was used in order to evaluate its usefulness in predicting the effects on soil due to various rates of loading and to repetitive loading. Field tests were conducted in two phases. The first phase included 24 CPMT tests, at the Texas A&M University research annex, which were designed to show 1) if the CPMT could be used to predict the effects on the soil due to both rate effects and repetitive loads; and 2) if the CPMT should be inserted into a prebored hole to the desired test depth or if the CPMT should be driven to the desired test depth. The soils at the research annex were a clay and a sand. The second phase included 32 CPMT tests at three sites throughout the state of Texas. Two of the sites were clay and the third site was sand. The CPMT test used at these sites was devised so that both rate effect and cyclic effect could be determined from a single test. Rate effects on the soil modulus were modeled using a viscoelastic model of the form EstEso = ttto−ncrp (1) while repetitive load effects on the soil modulus were modeled using a power law of the form EsNEs1 = N−n (2) It was concluded that a single CPMT test could be used to model both rate effects and cyclic effects on the soil modulus and that the most consistent method of inserting the probe was to place it in a prebored hole. It was also concluded that a linear relationship exists between the exponents n in both modeling equations and the normalized CPMT stress level.