Applied Mechanics and Materials Vols. 405-408

Abstract: Use FLAC3D, the interface command to define joint surface, set up rock mass models with 15 °, 30 °, 60 °, etc. different dip joint, and in accordance with the laboratory test data of rock and joint surface for a variety of strength and deformation parameters setting, carries on the numerical simulation of uniaxial compression. Got failure mode, plastic zone evolution and the stress strain curve of rock mass with different dip joint, and the result compared with the actual test has a higher similarity, to prove the feasibility of the numerical simulation method.

Abstract: Aiming at a deep foundation pit in soil-rock composition with weak intercalated layers, in this paper, using the limit-balance method and finite element method to analyze the stability and deformation. The safety factor of foundation pit under the absence of retaining is much less than 1 through the limit-balance method, but through some retaining measures can guarantee its safety. According to the excavation of the foundation pit in special geological conditions, it takes pile-anchor retaining structure in upper and soil nailing in the lower part. Using the finite element to carry out dynamic simulation for the whole project, the results show that: this form of retaining can be very good to ensure the excavation of the foundation pit in the geological conditions, and it may be helpful for similar projects

Abstract: Foundations are often subjected to complex dynamic stresses which result from ocean wave, vehicle or seismic loads. In this paper, four series of tests under different dynamic stress paths were carried out on Fujian standard sand with hollow cylinder apparatus, to investigate its liquefaction resistance. Test results showed different strength of specimens under different dynamic stress paths, when using the traditional evaluation index: maximum cyclic shear stress. A concept named as load efficiency (E) was proposed in this paper, which is defined as definite integral of dynamic shear stress on time in a single cycle. E is a new parameter to characterize liquefaction resistance of non-cohesive soil, attempting to normalize the effect of different shear modes, in which the shear stresses are constant or change periodically under different dynamic stress paths. Test results showed that in the isotropic consolidation condition, the relationship between E and failure cycle N_f is nearly linear in the dual-log coordinate.

Abstract: Iron tower foundations of transmission line located above goaf of coal mine generally use integral flexible concrete foundation or raft foundation to reduce uneven foundation settlement.When the tower is located at steep slope or restricted area, the above two basic foundation types require wide range of lower base surface, which causes widespread environmental damage.Consideratiing engineering practice, a new foundation type is proposed supplemented by theoretical analysis and economic analysis in this paper, which provides a new choice for foundation design in mountains areas above goaf of coal mine.

Abstract: The pile-soil interactions are constrained by the pile cap in pile groups with cap, while mutually independent in pile groups without cap. The mechanism of changing of NSF in pile groups with cap are analyzed briefly. The NSF behaviors of pile groups with cap under the condition of groundwater level lowering are analyzed by three-dimensional finite element method. The analysis shows that the NSF of pile groups with cap is generally similar to that of a single pile: as the working loads on cap increasing, the neutral point moves up, additional settlement increases and the downdrag decreases, though there are differences between piles in different positions. The constraints of settlement of piles in various positions by the cap are significant when the working load is not large, so that the neutral point of piles are almost coincident. As the working load increasing, the deformation of the cap increases and the neutral point of piles become more various, lowest for the corner pile, second for the perimeter pile and highest for the interior pile. The NSF of each pile in pile groups with cap mobilizes differently along the depth. It is mobilized most fully for the corner pile, second for the perimeter pile and least for the interior pile.

Abstract: The results of experimental research are presented and discussed with focus on the ground improvement effect of slurry with different kinds of vertical drains under new vacuum conditions. In these conditions, horizontal sand cushion, which is requested in regular vacuum preloading method, is cancelled. Vertical drains are connected with sealed pipes, so the vacuum head can be transmitted into vertical drains without decreasing. For the experimental research, slurry taken from reclaimed soil zone is placed into six model casing boxes. Different kinds of vertical drains (prefabricated vertical drains (PVDs) and sand drains) are installed into the soil with different spacing (0.4 m and 0.8 m). A vacuum pressure of 80 kPa was applied continuously for 90 days. The effect of filter type of PVD, type of vertical drain and drain spacing under new vacuum preloading condition to slurry soil improvement is examined. Test results show that this new vacuum preloading condition can transmit vacuum head into vertical drains efficiently and the effect of drain filter to slurry improvement is affected by the drain spacing.

Abstract: Based on the fluid-solid coupling theory, we study the stability of surrounding rock mass around underground oil storage in Huangdao, Shandong province, analyze the stress of the surrounding rock mass around three chambers and the displacement change of several key monitoring points after excavation and evaluate the stability of surrounding rock mass using COMSOL Multiphysics software. Research results show that the stress at both sides of the straight wall of cavern increases, especially obvious stress concentration forms at the corners of the cavern, and the surrounding rock mass moves towards the cavern after excavation. The stress and displacement of the surrounding rock mass will increase accordingly after setting the water curtains, but the change does not have a substantive impact on the stability of surrounding rock mass.

Abstract: In this paper, the Goodman element contact model is programmed on the second-development calculation platform offered by finite element software. Computation and analysis have been done so as to obtain the effect of contact parameters to the shear stress. The results show that, the subroutine can reflect the model’s nonlinear characteristic well. The order of the effects of parameters to shear stress is: φ>Rf >K>n; and when Rf increases, the shear stress decreases. These results can offer reference to direct shear tests to obtain the contact parameters.

Abstract: The transfer mechanism of super-large deep-water pile group foundation is quite complex, the traditional design and construction technology has been unable to meet building requirements while the applications of new technologies and new processes are lacking technical support. At present, the informatization in whole construction process basing on safety monitoring is an effective way to solve the problem. To ensure the safety monitoring system to work properly, the sensors are often redundant layout. however, the redundant data would cause data inconsistency and even contradiction. In order to eliminate this contradiction and to have the real force characteristics of pile group foundation, the valuation fusion algorithm was used in mult-sensors data fusion analysis. The result shows that the axial force and deformation of pile group foundation meet true response better after fusion.

Abstract: For difference of elevation of mountain slope, four legs of iron tower are not in the same plane.In order to reduce the excavation of the base surface and damage to the environment, several foundation types are widely used to adapt with the terrain changes,such as comprehensive unequal legs,unequal Foundation, outfitting extra legs and so on.When the tower is located in steep slope of rocky area,common foundation types in use will bring a large area of ​​earth and rock excavation, construction difficulties, high-risk, poor basic indicators, greater damage to the environment.Consideratiing engineering practice, a new foundation type is proposed in this paper supplemented by theoretical analysis and economic analysis, which takes full advantage of the terrain and rock properties and provides a new choice for foundation design on steep slope in mountains areas.