Numerical Verification of the Concentric Arches Model for Geosynthetic-Reinforced Pile-Supported Embankments: Applicability and Limitations

In this study, a series of 3D FE simulations of a geosynthetic-reinforced pile-supported embankment (GRPE) design were conducted. The effect of the subsoil stiffness, friction and dilation angles of the fill, the fill height, the pile spacing, the surcharge load on the embankment, and the anisotropic tensile stiffness of the GR, the ground reaction curve (GRC), and the interfacial responses between the fill material and geosynthetic reinforcement (GR) were scrutinized. The numerical results showed how transfer of the vertical load towards the piles (load part A) and the related soil arches change with the subsoil stiffness, geometric parameters, and the vertical pressure on the embankment. Furthermore, the vertical load transferred through the GR (load part B) is reduced significantly with increasing subsoil stiffness, while the load part carried by the subsoil increases (load part C). The numerical results showed that the vertical stress distribution on the GR changes from an inverse-triangular shape for low subsoil stiffness to a uniform shape for high subsoil stiffness. This matches perfectly with the Concentric Arches model. For low subsoil stiffness, the tensile strains of the GR are concentrated at the corner of a square pile cap.

Research on Influence of Road Tunnels with Different Lanes on Surrounding Rock Characteristic Curve

Convergence confinement method is an important guidance method for tunnel construction and support design. Numerical simulation method was used to comparatively analyze the ground reaction curve and the plastic zone under different rock grade and roadway tunnel size. The results show that the change of tunnel size has different effects on the maximum deformation of the tunnel arch crown, the ground reaction curve and the plastic zone range. Finally, some suggestions were put forward for the construction and optimization of the large span arch tunnel support structure. The research results may provide some guidance for related engineering

Load-transfer platform behaviour in embankments supported on semi-rigid columns: implications of the ground reaction curve

Post-construction data from an instrumented geosynthetic reinforced column supported embankment (GRCSE) on drilled displacement columns in Melbourne, Australia, show the time-dependent development of arching over the 2 year monitoring period and a strong relationship between the development of arching stresses and subsoil settlement. A ground reaction curve is adopted to describe the development of arching stresses and good agreement is found for the period observed thus far. Predictions of arching stresses and load-transfer platform behaviour are presented for the remaining design life. Four phases of arching stress development (initial, maximum, load-recovery, and creep strain phases) are shown to describe the time-dependent, and subsoil-dependent, development of arching stresses that can be expected to occur in many field embankments. Of the four phases, the load-recovery phase is the most important with respect to load-transfer platform design, as it predicts the breakdown of arching stresses in the long term due to increasing subsoil settlement. This has important implications in assessing the appropriate design stress for the geosynthetic reinforcement layers, but also the deformation of the load-transfer platform in the long term.

A novel solution for ground reaction curve of tunnels in elastoplastic strain softening rock masses

Ground Reaction Curve (GRC) is one of the most important elements of convergence-confinement method generally used to design tunnels. Realistic presentation of GRC is usually assessed based on the advanced rock strength criteria, also, rock mass behavior (including plasticity and softening treatments). Since taking these parameters into ac­count is not simply possible for practitioners and needs complicated coupled theoretical-numerical solutions, this paper presents a simple novel approach based on Evolutionary Polynomial Regression to determine GRC of rock masses obeying both Mohr-Coulomb and Hoek-Brown criteria and strain softening behaviors. The proposed models accurately present support pressures based on radial displacement, rock mass strength and softening parameter (determination coefficient of 97.98% and 94.2% respectively for Mohr-Coulomb and Hoek-Brown strain softening materials). The ac­curacy of the proposed equations are approved through comparing the EPR developed GRCs with the ground reaction curves available in the literature. Besides, the sensitivity analysis is carried out and in-situ stress, residual Hoek-Brown’s m constant and residual dilation angle are introduced as parameters with the most influence on the support pressure in Hoek-Brown and peak and residual geological strength index are the most affective parameters on the support pressure of tunnels in the strain softening Mohr-Coulomb rock mass.