Applied Mechanics and Materials Vols. 580-583

Abstract: The basalt residual soil of high slope of BiWei highway in Guizhou province belongs to regional special soil. Comprehensive and systematic evaluation for engineering geologic characteristics of residual soil on basalt is necessary to the construction in this area and geological engineering investigation. Kaolinite is dominant in clay mineral of this soil, which has a higher clay particle content. The special material composition and structural morphology make it have the physical properties of high porosity, low density and high water content. But it has mechanical properties of higher strength. The soil has a low expansibility and weak water-resistance. Moreover, the soil is sensitive to environmental factors such as temperature and humidity. The mechanical properties become weak after soaking, leading to a larger collapse deformation and a heavy disintegration. Therefore, it is important to focus on the engineering disasters caused by rain water for example.

Abstract: Precast thin-wall steel and spun concrete composite pile (TSC pile) is a kind of new type of steel-concrete composite pile whose bearing performance is between steel pile and concrete pile. This article adopted FEM software to set up 3D TSC pile model to analyze its performance. Through the comparison with actual pure bending bearing experiment results, the model’s reliability was verified and the results showed that the model was reliable. Then lots of bending bearing capacity contrast calculations were conducted by using different cross section parameters (outside diameter, concrete pipe’s wall thickness and steel pipe’s wall thickness), and the influences of these parameters on bending resistance of TSC pile were discussed. The results showed that: with the increase of outside diameter, concrete pipe’s wall thickness and steel pipe’s wall thickness, TSC pile’s ultimate flexural bearing capacity increased. The influences of different parameters were not the same, outside diameter was the most important parameter, then concrete pipe’s wall thickness, and the last one was steel pipe’s wall thickness.

Abstract: This paper elaborate the bad geological characteristic and the huge disaster caused by expansive soil. When constructing the road or railway in expansive soil area, the roadbed disease such as slope stability failure,roadbed settlement,mud pumping,ballast bag and so on is elaborated. The expansion and shrinkage mechanism of expansive soil has been studied from such aspects as physical-chemistry-mechanics effect, material composition, external influencing factors and so on. In expansive soil area, such expansive soil treatment and reinforcement methods as physical improvement, chemistry improvement, biological improvement are summarized and proposed.

Abstract: In the excavation process of Foundation Pit in Soft Soil area, it will cause the large uplift of stand column, and may cause the instability and failure of foundation pit in case of being serious; but the additional internal force of support system caused by the uplift and sinking of stand column currently has no practical calculation model in the foundation pit design. This article discusses the reason and mechanism for uplift of stand column in the foundation pit, proposes the simplified calculation method of estimating the additional bending moment of inner support through uplift of stand column in allusion to two main influence factors of bottom heave and vertical load caused by the excavation of foundation pit, inversely calculates the permissible additional bending moment of inner support based on this, verifies by combining the monitoring data for uplift of stand column in the actual project, and finally, further proposes the project measures corresponding to the uplift of stand column, hoping to provide beneficial reference for the similar project.

Abstract: Early warning thresholds for slope instability were discussed in this study by means of rheological tests and field measurements due to availability and effectiveness of the data. Five warning levels were specified to take proper measures in different emergent cases. The left bank slope of Jinping I hydropower station was studied as an instance to implement the strategies introduced in the study. The surface displacement thresholds were obtained by analyzing long-term observed displacements (the former three warning levels) and the rheological tests on the rock mass (the last two levels). The results gave out that the thresholds of surface displacement rate for different warning levels were 0.30mm/d, 1.15mm/d, 3.00mm/d and 5.00mm/d. These results could be potential references for other projects.

Abstract: Evaluation of slope stability is a complex system problem with uncertainties. Based on the Projection Pursuit (PP), the Particle Swarm Optimization (PSO) and the Logistic Curve Function (LCF), a new model for evaluation of slope stability is developed, which is referred as Projection Pursuit based on Particle Swarm Optimization (PSO-PP). The model, on the one hand, uses PSO to optimize the projection index function and the parameters of LCF. Thus it would ensure the accuracy of the parameters used in the model. On the other hand, the nonlinear relationship between projection values and empirical grades is established according to LCF. The test results of the model show that the model has a very good precision. In this study, the evaluation results obtained by applying the model developed here into Jinping I site hydropower plant are well consistent with the practice situation. It indicates that the model here is feasible and effective in the evaluation of slope stability.

Abstract: On basis of geological hazard survey for dangerous tower foundations of transmission line in the sphere of influence of some goaf, stability analysis is conducted for dangerous towers by use of statistical approach in accordance with relevant regulations, to propose recommended treatment measures. The method suggested in this paper can provide references for stability analysis on dangerous towers of transmission lines. The recommended measures can be served as a reference for actual projects.

Abstract: Due to the existence of underground building, the distribution of displacement field of adjacent foundation pit is obviously different from that of general foundation pit, and it is of great significance to correctly understand the sheltering effect of underground building to displacement field for determining the protection class of foundation pit while supporting design of foundation pit, and protecting the safety of metro station built near and surrounding buildings during the construction. Relying on the foundation pit project of metro station and combining the sensitivity theory through mechanism analysis, this article discovers that the sheltering effect is most obvious when the spacing between the underground building and retaining wall of foundation pit is 0.5H, and the sheltering effect can be ignored when the distance is more than 2H.

Abstract: EPS is silt mixing light-weight soil by expanded polystyrene, curing agent, mixture mixing and has a certain strength, lightweight synthetic packing. This article is based on laboratory test, using the uniaxial and triaxial compression test on the relationship between stress and strain, research has shown that the strain values are greatly influenced by the EPS content ratio, strength is mainly composed of cement mixing ratio control. Triaxial test results show that only when the cement mixing is larger, mixed soil shear strength characteristics with general soil has a great deal of similarity.

Abstract: Composite soil nailing technology is a new technology which developed on the basis of the soil nailing supporting technology. This new technology has a very important practical significance to the construction, for which the scale is larger and larger, the condition is more and more complex and the excavation of foundation is more and more deep. Composite soil nailing technique is mainly introduced in this paper by its main form of structure and the main principle, which draw a conclusion that different forms of the combination of support types have different effects on the stability of structure, by analyzing the support stability. This thesis shows that we should adjust measures to local conditions, choose the right organic combination. At the same time it also provides the basis for the practical application of engineering support.