Applied Mechanics and Materials Vols. 580-583

Abstract: Based on theoretical analysis and experimental result, the principle as well as the interaction between pile and soil, the design parameters of composite foundation with cement-fly ash-gravel piles (CFG piles for short) are optimized, which are pile length, pile diameter, pile spacing, pile strength and thickness of cushion layer, in order to put forward the reasonable design parameters for reaching economic and reasonable target. Through the optimized analysis, it is put forward that bearing stratum of pile tip should select a relatively better soil layer, the diameter of CFG pile is usually appropriately to select between 350mm and 500mm, it is usually appropriately to select larger pile spacing under the permissible range between 3d and 5d being ruled by standard, it is appropriately to enlarge the pile diameter to reduce the requirement of pile strength in high rise and super high rise building which requiring bearing capacity of single pile is high, and the thickness of cushion layer is appropriately to select between 0.4 and 0.6 times of the pile diameter.

Abstract: Composite foundation can be designed as long and short piles that lie on different bearing strata with high bearing capacities. Researches have shown that for foundation with sufficient stiffness, the ratio of the thickness of cushion to pile diameter (thickness-diameter ratio) plays an important role on the exertion of bearing capacities of pile and soil between piles. Traditional method just applies equal thickness-diameter ratio to design composite foundation with long and short piles, which hinders the exertion of bearing capacity of composite foundation. To overcome this defect, this paper studies the relations between thickness-diameter ratio and the exertions of bearing capacities of pile and soil between piles. The design method of thickness-diameter ratio for composite foundation with long and short piles is also proposed in this study.

Abstract: The work condition of the highway, which is usually built in mountainous regions, is complex relative to the ordinary road. Slope instability accident caused by the seepage of rainwater usually occurred in the rainy season. The mechanism for seepage failure of slope was investigated by used the Mohr-Coulomb criterion and the principle of effective stress. The effect of rain intensity on slope stability was equivalently instead by the effect of moisture content on slope stability. The influence of moisture content on the safety factor of slope stability was further calculated according to the Bishop’s method. The degeneration of safety factor follow to the moisture content was presented in the percentage.

Abstract: The pile will have a large lateral displacement in soft soil under the role of heaped load. Based on Biot consolidation theory, combined with a certain highway project, a three-dimensional FEM model is established, the process that the soil lateral deformation under heaped load lead to the pile side displacement was simulated. On the ground of the former result, the influence factors for the displacement of pile top and the pile displacement field distribution are analysed. The results show that, the building load area, load grade and the distance from loading area to pile have a major influence on the pile side displacement. On the other hand, the load on pile top have a very small contribution for stability of anti side displacement. The buildings nearby the area of pile foundation should be given attention in practical engineering.

Abstract: Determining the freezing pipe spacing, the freezing reinforcement required range and method, acquiring the development and distribution patterns of frozen soil wall temperature field are the key issues needed to be addressed when using vertical freezing method for the soil reinforcement at shield shaft. Based on the shield launching project of the cross-river shield tunnel of Nanjing subway line 10 and the finite element numerical analysis software, the development and distribution patterns of different distance between freezing pipes of the vertical frozen wall are studied. The numerical simulation shows that, it is feasible to use the numerical model to simulate the temperature field of vertical frozen wall. Decreasing the distance between freezing pipes causes a greater impact on the temperature field. When freezing pipe spacing increases to 0.1m, frozen wall cross-lap time increases of about 1 day. With the freezing pipe spacing increasing, the cross-lap time increases linearly. The temperature of frozen wall decreases with the distance between freezing pipes decreasing, and the strength of frozen wall is more uniform. Results and conclusions form this research may play a useful role to aid designs of similar projects in future.

Abstract: On the basis of engineering project using underwater vacuum preloading method to strengthening the soft foundation, under the specific geological conditionsthis article analyzes the construction technology and reinforcement mechanism of underwater vacuum preloading of the soft soil foundation. By indoor soil test of Reinforcement of soil before and after processing, compared the change and improve of soil shear strength indexes before and after the reinforcement, it is verified that the underwater vacuum preloading method is a effective mean in handing soft ground, and can be further promoted as a means of handling soft ground along the coastal area of China.

Abstract: The reinforced soil foundations have been widely used in various geotechnical engineering applications, such as bridge approach slab, bridge abutment and so on. However, many problems of reinforced foundation still need to be solved and the behavior of the reinforced foundation requires further study. Therefore, finite element analyses were conducted on unreinforced and reinforced clay subgrade soil to evaluate the influence of various factors affecting the performance of strip footing on studied soils. Conclusions are drawn: the effective reinforcement depth is about 1.5B for the reinforced soil and it is independent of the geogrid type; At a given settlement, the bearing capacity of the footing decreases with the increase in reinforcement spacing, with larger decrease rates at small spacings; A geogrid with a tensile modulus ranging from 5MPa to 25MPa will maximize the benefits of the reinforced soil footing, etc.

Abstract: Combined with the engineering geological conditions and geological characteristics of soil-like slope in a certain open-pit copper mine, based on the experiments and theoretical analysis, the instability mechanism of soil-like slope under the action of acid mine wastewater is researched. Because the acid wastewater goes into the weak structural plane, reacting with the constitutional materials and fillings in slopes, the react change the microstructure of the rock and soil, and replace, dissolve the components, causing the cohesion and internal friction angle of slope reducing eventually and slope failure.

Abstract: The optimum design of final highwall is a multivariable and complex technical problem that every change in any factor will influence the stable state. Based on the history-case, this paper applied the critical sliding field to search the critical slip and evaluate the stability of slope with different geometric forms. Comprehensively compared the global and local slope stability and its economic benefits, finally achieved the optimum design of final highwall.

Abstract: This paper studied on the underwater vibrating compaction technology of scattering-filling rubble stone layer. At HongKong-Zhuhai-Macao bridge project, in order to satisfy the project time limit, underwater vibrating compaction technology with hydraulic hammer instead of conventional dynamic compaction technology was used to tamp scattering-filling rubble stone layer with no dead angle in a short time. Owing to the shortage of engineering example, the theoretical analysis was needed before field application. In this paper, the rubble stone layer and the vibration system were simplified to a mechanical model. Vibration system’s work on rubble stone was obtained by mathematical derivation, and effects of parameters were analyzed. The result shows that work on scattering-filling rubble stone layer increases with the increase of system quality, equivalent damping, exciting force and angular velocity and decreases with the increase of equivalent stiffness, water stiffness and buoyancy.