Research on 3d elastoplastic numerical analysis of settlement joint of shield tunnel based on the interaction between soil and structure
Considering the effect on uneven settlement of tunnel longitudinal stratum, a 3d elastoplastic numerical model is established for the arrangement of settlement joint and the calculation of force and deformation of tunnel longitudinal structure based on the interaction between soil and structure. In the FEM calculation model, soil material is elastoplastic, the soil constitutive model selected Mohr Coulomb, the element type of soil choose a three-dimensional solid element, the element type of segment structure use space shell element, and settlement joint use three-dimensional linear elastic spring. Calculation shows that, this calculation model is able to fully consider the impact of tunnel the uneven settlement of all factors, and may better simulate the vertical force and deformation behavior of tunnel structure in complex ground formation conditions. Research conclusion gives the vertical force and deformation of the tunnel structure under the condition of different set of settlement joint, and has an important reference value for the future design and construction of the tunnel lining structure.
Numerical Study on the Effect of Grouting on Long-Term Settlement of Tunnels in Clay
The long-term settlements over tunnels can be rather significant, particularly when tunnels are embedded in soft and compressible soils. The influence of grouting on the evolution of long-term surface settlement, as well as ground loss, is simulated by imposing prescribed volumetric strain on the disturbed area around the tunnel due to shield tunneling. The volumetric strain could be detected from the grouting ratio of grouting volume and the volume of the physical gap of shield tunnel. Finally, some conclusions are drawn from the numerical simulations.
Cleat mineralization of Upper Permian Baralaba/Rangal Coal Measures, Bowen Basin, Australia
Abstract Coals from the Permo-Triassic Bowen Basin have been investigated using a variety of complementary analytical techniques. Face cleat minerals in the studied samples are dominated by authigenic clays, notably pure illite or illite-chlorite mixtures. Butt cleats and joints are dominated by carbonates, mostly calcite with less abundant ferroan calcite, ankerite and siderite. K/Ar ages of cleat-fill illites and one fracture illite-smectite fill indicate three phases of illite formation during the Triassic: (1) an early phase with ages clustered around 244 Ma ago; (2) a second phase about 232 Ma ago; and (3) the latest phase about 219 Ma ago. Thermal modelling of selected boreholes from the study area and other geological data indicate that the first phase of illitization occurred when the coal seams were about 1000 m below the surface and at a temperature of between 70 and 80°C, at a time when the basin was rapidly subsiding. These early illites were stable and retained their 1M polytype even after being exposed to temperatures of 150–190°C during maximum burial in the southeastern Bowen Basin. The second phase of illitization (at 232±3) occurred at about the time of maximum burial. The latest phase took place between 223±3 and 212±3 Ma ago and occurred in a wider temperature range (between 170 and 100°C) during a rapid uplift in the Late Triassic. The Bowen Basin area experienced a second cycle of subsidence that commenced in the Early Jurassic with the formation of the Surat Basin, which overlies the Bowen Basin and forms part of the Great Artesian Basin system. Regional uplift and erosion in middle Cretaceous times terminated sediment accumulation in the Surat Basin. During the second cycle of burial widespread carbonate mineralization in butt-cleats and joints took place. Calcite fluid inclusions indicate that calcite was precipitated from meteoric water at about 80°C. The widespread carbonate mineralization in butt cleats and the near-absence of carbonates in the face cleats is here attributed to permeability anisotropy, caused by a change in the direction of lateral compressive stress during Jurassic-Cretaceous times relative to that during the Triassic Hunter-Bowen Orogeny.