Elasto‐plastic model for cement‐treated sand

Abstract

SUMMARYThis paper presents an elasto-plastic model for non-linear analyses of cement-treated sand. Various laboratory tests were systematically carried out to investigate the pre-peak and post-peak behaviours of a cement-treated sand. On the basis of these experimental results, the new model was built within the framework of a relatively simple elasto-plastic theory.Two failure criteria are employed to express tensile and shear failure characteristics observed in the experimental results of the cement-treated sand. The proposed model can describe strain-hardening and strain-softening responses under both failure modes. In the strain-softening rules, the smeared crack concept is used, and a characteristic length is considered to avoid the issue of mesh-size dependency. Since the failure criterion and strain-hardening/softening rules are based on the experimental evidences, the model is relatively easy to understand and the parameters used in the model have clear physical meaning. The proposed model was applied to simulate the behaviour of cement-treated sand in various laboratory tests, allowing for a reasonable comprehensive evaluation. It was demonstrated that the proposed model is suitable for describing both the tensile and shear failure behaviours of cement-treated sand.

Finite Element Analysis of Lattice-Shaped Ground Improvement by Cement-Mixing for Liquefaction Mitigation

“…Two models, an elastic model and an elasto-plastic model, were used for assessing the behavior of the soil improved by cement-mixing. The elasto-plastic model can describe the behavior of cement-treated soil under a general 3D stress state (Namikawa and Mihira, 2007). It models tensile and shear strain-softening responses in localization zones after peak stress states.…”

“…The elastic model was used for the improved soil in analyses 1a, 2a and 3a. These analyses require two parameters, elastic modulus E and Poisson's ratio n. The values of E and n for the cementtreated soil with the unconˆned compression strength qu＝2 MPa (analyses 1a and 2a) were determined from laboratory test results (Mihira et al, 2003;Namikawa and Mihira, 2007). Assuming that E is proportional to qu, the value of E for the cement-treated soil with q u ＝5 MPa (case 3a) was evaluated from that for the cement-treated soil with qu＝2 MPa.…”

“…Parameters for the cementtreated soil with the unconˆned compression strength qu＝2 MPa (analysis 2b) were determined using laboratory test results (Mihira et al, 2003;Namikawa and Koseki, 2006;Namikawa and Mihira, 2007). Assuming that the elastic modulus E, the cohesion c, the tensile strength Tf, and the fracture energy Gf were proportional to qu, these values for the cement-treated soil with qu＝5 MPa were evaluated from those for the cement-treated soil with qu＝2 MPa.…”

“…The applicability of this elasto-plastic model for the cementtreated sand was conˆrmed by simulating the triaxial compression, triaxial tension, plane strain compression and bending tests on cement-treated sands. These simulation results are available elsewhere (Namikawa and Mihira, 2007).…”

Simplifying calibration of bonded elasto-plastic models

“…[2]) have been applied to model cement treated clay ( [3]). Similarly, and because improved soils have analogies with concrete, cemented soils have been represented adapting models originally developed for concrete [4]. Taking a different perspective, a number of researchers have successfully extended elasto-plastic models for soils of the critical state tradition to represent artificially cemented clays [5] and silts [6].…”