Advanced Materials Research Vols. 250-253

Abstract: In order to assess theoretically the expansive strain of concrete caused by the ettringite formation and growth under the sulfate attack, some models are proposed to investigate the strain responses of concrete exposed to the sulfate solutions. Firstly, an 1-D nonlinear and nonsteady diffusion-reaction equation of sulfate ion in concrete is proposed; Secondly, based on chemical reactions between sulfate and aluminates in concrete, the expansive strain is obtained due to the ettringite growth resulting in concrete expansion. Thirdly, numerical simulations are carried out to analyze the formation process of the concrete expansive strain under the sulfate solution, and results show that the models can be used to predict the concrete responses with the diffusion time, such as the distribution concentration of sulfate ion, dissipated concentration of the calcium aluminates, expansion strain of concrete due to the formation and growth of ettringite.

Abstract: Ground subsidence is one of the main geological hazards in Shanghai. The ground subsidence is caused by pumping groundwater greatly. In the past, studies of ground subsidence in Shanghai were mostly taken for the ground subsidence caused by pumping confined water in Puxi. And ground subsidence caused by pumping phreatic water was rarely studied. Dewatering preloading is a new technology for soft soil treatment. The monitoring of ground water level, ground subsidence, pore water pressure in the process of dewatering preloading test for a soft soil treatment project in Pudong showed that pumping phreatic water can also cause ground subsidence. The ground subsidence caused by pumping phreatic water was analyzed in this paper. The relationship between phreatic water level and ground subsidence was obtained.

Abstract: The consolidation coefficient, permeability coefficient and other parameters were calculated out based on field measurement data of pore water pressure in this paper. The post-construction settlement behaviour of dynamically consolidated foundation was also simulated. The simulation results were consistent with the actual observation results. The method of this paper provides an effective way for the prediction of post-construction settlement of dynamically consolidated foundation.

Abstract: The paper examines the effect of the corrosion types of reinforcing steel on the deterioration of shear strength of corroded reinforce concrete (RC) beams. Three possible types of corrosion, i.e., uniform (or general), pitting (or localized) and hybrid corrosion, for RC beams exposed to de-icing salts or sea environments are considered. From the investigation of the present paper, it can be concluded that the corrosion types have great effect on the time-dependent shear strength of a corroded RC beam. Generally, the shear strength degraded fastest for hybrid corrosion among the three corrosion types. When the corrosion rate is relative small, the deterioration of the shear strength for the uniform corrosion is greater than that for pitting corrosion. However, when the corrosion rate becomes larger, the deterioration of the shear strength for the pitting corrosion is greater than that for uniform corrosion as corrosion propagates.

Abstract: In this paper, the proposed idea of producing fully-enclosed composite cable with CFRP coupling of high-tensile steel wires and the forming technology of the fully-enclosed composite cable body were introduced. The coordination mechanism of the fully-enclosed composite cable, the requirement of equal elastic modulus between high strength steel wire bundle and CFRP were investigated theoretically. We have come to the follwing conclusions: (1) Carbon fiber has the same strain with the high-tensile steel wire under the tension of whole anchorage. (2) The distribution of the force of the composite cable is in accordance with the axial stiffness between the carbon fiber with high-tensile steel wire. (3) To achieve a good synergy between the carbon fiber with high-tensile steel wire, similar or equivalent elastic modulus is required. (4) The stress ratio between carbon fiber and high-tensile steel wire in the fully-enclosed composite cable in engineering application should be controlled around 0.5.

Abstract: This paper aims to study the strain softening behavior of soft rock. A modified equation of unified strength theory is proposed that is convenient to be applied in geotechnical engineering where compression is customarily taken as positive. And also the limit line on deviatoric plane of this modified equation is derived and introduced into the three dimensional (3D) elastic viscoplastic constitutive model of Yin and Graham. Parameters of the model are determined from experiments of the diatom soft rock specimens. Numerical simulations are performed to compare the strain softening behavior predicted in this paper and triaxial experimental results. Simulation results show that the proposed model can accurately describe the strain softening of soft rock.

Abstract: The Shuibuya Dam is the highest concrete faced rockfill dam (the height is 233m) in the world. The dam site is located in Enshi Autonomous Prefecture, Hubei province, china. The reservoir level is a maximum of 400m. When the dam was partially completed, water impoundment was started. On May 10, 2007, when the reservoir level achieved at 289m, a landslide located on the bank of Modao-he River moved rapidly, a tributary of the Qingjiang River. 14 houses collapsed and moved into the river, but nobody was killed due to timely geological prediction. For the purposes of landslide disaster mitigation in the reservoir areas and identification of landslide movement and deformation caused by the change of reservoir level, some researches were conducted, such as geological exploration, some soil tests and numerical simulation and monitoring system. In this paper, the causes of landslides and slope failure mechanism and the stability of slope were simulated by using DDA method and FLAC^3D for the different reservoir’s level.

Abstract: Indexes of coarse aggregate, such as powder content, sediment percentage, maximum particle size, gradation and coarse aggregate volume ratio, are experimented and analyzed for impermeability, cracking resistance and freezing and thawing. Recommendation value based concrete durability is provided. (1) Coarse aggregate should be washed to keep surface clean during producing. (2) Clay content should not exceed 1%. (3) Coarse aggregate maximum size should not be greater than 26.5mm. 19mm and 26.5mm is the beat generally. (4) Smaller equivalent size should be used within the same gradation. (5) Coarse aggregate volume ratio is not more than 0.75 in improving anti-cracking performance for earlier concrete and in 0.70 to 0.75 in increasing impermeability of concrete.

Abstract: A probabilistic analysis procedure and related algorithms were based on the Monte Carlo simulation method that considers the variability of soil properties in this paper. A homogenous slope example provide insight into the effects of uncertainty due to the variability of soil properties on slope stability .Taking soil parameters cohesion c, friction angle, gravity γ as the basic random variables, the reliability index are calculated using Monte Carlo simulation method taking into account the uncertainties of these basic random variables. The calculated results are compared for four recognized methods of slope stability, which are Ordinary method, simplified Bishop method, simplified Janbu method and Morgenstern Price method. And the influence of soil parameters’ probability distribution model (i.e. the normal distribution and the log–normal distribution), variation coefficient, mean value, correlation between parameters on the reliability index of slope is discussed. The study shows that different soil properties have different influence degree on the reliability index with regard to the slope reliability analysis.

Abstract: On the base of the equilibrium of the whole force equilibrium, the whole moment equilibrium of the slope, and the force equilibrium of the differential column, this paper provides a general form of the 3D limit equilibrium which includes three equations. Through these equations and each assumption of the classical methods, their analytic forms can be gotten. Thus, not only the computation quantities of the classical method can be decreased greatly, but also the programming of them become very easy, and the computation efficiency also can be developed. At last, through the example in Zhang Xing’s paper and the analytic forms of the classical methods, this paper analyzes the effect of the sliding body width, the shearing strength parameters and the shearing force direction on the safety factor.