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Polymer geosynthetics exhibit obvious viscous behaviors related to the loading strain rate. A nonlinear three-component elasto-viscoplastic constitutive model is found relevant to simulate these rate-dependent load-strain behaviors of polymer geosynthetics under complex loading conditions, including variable loading rate, creep and stress relaxation. For the purpose of the wide use of this model, it is implemented into the finite element analysis software ABAQUS through its user material subroutine (UMAT) connector. The algorithm used for the numerical integration of the constitutive model is return mapping method and is presented in detail in this paper. Then FEM simulations are performed to validate that this model is very capable of simulating the viscous behaviors of geosynthetics under arbitrary loading conditions.

The consolidation and pressure dissipation of the generally adopted cement based grout injected into the tail void during simultaneous backfill grouting in shield tunneling are influenced by many factors, such as grout characteristics, ground permeability, pore water pressure (PWP), dimension of the initial grout pressure, and various loads acted on the lining. Based on the typical simultaneous backfill grouting parameters in soft soils in Shanghai, and excluding the influence of grout hardening, using the theory of fluid mechanics and elastic mechanics, the principle of grout consolidation in tail void is firstly analyzed in this paper, and the changes of grout cake's thickness (GCT) and grout pressure (GP) with time are clarified. Then, as for grout pressure dissipation (GPD), the influences from ground osmotic resistance, PWP and dimension of the initial GP are discussed. The following conclusions are drawn: the ground osmotic resistance can obviously delay grout consolidation, but not the final consolidation state; the increment of soil shear modulus can accelerate the grout pressure dissipation speed (GPDS); consolidation process can be obviously restrained by the increment of PWP; and there is a positive relationship between the initial GPDS and the dimension of GP.

This paper investigated the effectiveness of open-trench wave barriers in reducing the movements of sheet pile walls during deep dynamic compaction (DDC), by isolating (screening) the energy waves generated in DDC impact. This investigation was achieved by a series of finite element analyses. The open trenches with different cross-section shapes were investigated. The dimensional effects of trenches were analyzed and discussed, and then the isolation efficiencies of the different trenches were compared. The numerical results indicated that excavating an open trench in front of the retaining walls is an effective measure to reduce wall movements during DDC. For the investigated open trenches, increasing trench depth or trench width can efficiently improve their isolation efficiencies, while the cross-section shapes of the trenches have no apparent influences.

The shield tail void formed in unit time in tunneling is simplified as a three-dimensional annular space with shied advancing at certain speed. As the filling process cannot be observed in-situ, it is very difficult to simulate it in detail. Taking the cementitious grouts used in grouting injection as Newton fluid and Bingham fluid respectively, based on the typical four grouting holes design, the distribution of grouts pressure in cross section is obtained with the diffusion model of grouts pressure and the principle of superposition. With further consideration of grouts infiltration into the surrounding strata and its hardening process, the distribution of grouts pressure in longitudinal section is obtained. Therefore, the diffusion model of grouts pressure for simultaneous backfilling grouting in shield tunneling is founded. Finally, the comparison between theoretical result and the site observation is made.

It is well known that the deformation and strength characteristics of sand are very complicated, and time effects and strain localization are two of the most important aspects. A non-linear three-component rheology model consisting of a hypo-elastic component connected in series to a combination of non-linear inviscid and viscous components connected in parallel is proposed, which can take into account multi-factor influence on the deformation and strength characteristics of sandy soils. The inviscid component is described by an isotropic, energy-based hardening and softening, and non-associated energy model, while the viscous component is formulated based on the strain rate-dependent behavior of sandy soils. A finite element method (FEM) code incorporating the aforementioned model is validated by simulating the physical plane strain compression (PSC) tests on sand. It is shown that the proposed model can much better simulate the deformation and strength characteristics of sand, especially for the rate-dependent behaviors and strain localization into a shear band.

Based on the results from the isotropic loading-unloading tests and a series of plane strain compression tests along different stress path on Toyoura sand, a couple of hardening functions respectively for shear and volumetric plastic strain for sand is introduced in the framework of double hardening elasto-plastic constitutive model. A modified form of plastic compressive strain energy, which is stress path-independent, and a volumetric yielding locus compose the compression hardening model. Another modified plastic shear strain energy, which is also stress path-independent, and a shear yielding locus compose the shear hardening model. Then, the plastic strains can be described as the sum of two independent parts. Based on the above, a double modified plastic work-hardening constitutive model for sandy soils is proposed. It is shown that, based on the direct comparisons between the results from the numerical calculation and corresponding drained plane strain compression tests on Toyoura sand, the above-proposed constitutive model could reasonably simulate the deformation and strength behavior of sand with different stress-path.

This paper investigated the densification effects of deep dynamic compaction (DDC) and vibratory compaction on loose saturated sands, which were based on two well-documented case histories. This investigation was carried out by examining pre- and post-compaction cone penetration testing (CPT) results. The CPT results indicated that under the same design earthquake excitation, the sands treated by DDC were densified to the level of resisting potential liquefaction, while, the sands were still liquefiable after vibratory compaction.