Applied Mechanics and Materials Vols. 256-259

Abstract: Land subsidence as one of geological disasters, due to the characteristics and specificity hydrogeology, which results in the differences of subsidence in different regions. Changzhou City, in Jiangsu province, in China, underlain by a multi-layered aquifer system in Quaternary sediments in the Great Yangtze River Delta region. Take into account geological characteristics and mechanisms, the Changzhou layers can be divided respectively into four soil stratifications: phreatic aquifer, Part I aquifer ,Part II aquifer ,and substratum. According to the monitoring data of bedrock bench mark at Changzhou Qingliang primary school, get the mechanism of water-soil interaction and the law between land subsidence and water level change, and establishes numerical coupling model and simulates, that can evaluate and predict Changzhou land subsidence.

Abstract: Large diameter and thin thickness are the main characteristics of the steel pipe piles in offshore engineering. Before piling a pile, heavy hammer will be placed on the top of it, which may emerge a serious risk in pile buckling. A three dimensional finite element model of pile and soil was established for a case study. The modified Riks method which can automatically search a suitable increment factor of loads is adopted to assess the stability of the pile, and the geometric nonlinearity and pile-soil interaction were both considered. The practical example shows that the critical load considering pile-soil interaction is much smaller than that in a fixed constraint.

Abstract: Northwest Hubei province is located in Mount Wudang metamorphic zone, where the geological conditions are very complex. The carbonaceous schist is relatively rare in this area, however, compared with other schists, it has some quite special characteristics. This paper focuses on lithologic features, physical and mechanical characteristics of carbonaceous schist, and Huashigou tunnel is researched as the engineering background. Analysis of carbonaceous schist shows that it has typical rheological, anisotropic and water-sensitive properties. Through a large number of monitoring measurement data analysis, deformation law of carbonaceous schist are summarized.

Abstract: Based on observation data about foundation settlement of Ji-He expressway in Shandong province,according to the theory of soil mechanics,deduced the prediction model of foundation settlement in linear loading condition.Verified its reliability combined with engineering example.Analyzed the influence factors of key parameters and the causes of errors in the model.The model can be used to estimate the foundation settlement and the process of settlement in the later period and after construction, control embankment filling and pavement construction progress. Providing the basis for evaluating the quality of highway construction and formulate the maintenance measures after construction.

Abstract: Hydrophilic characteristic of silt soil in Yellow River alluvial plain was studied in order to reveal the water content changes of silt. Then strength tests were used to research how engineering parameters such as elastic modulus, cohesion and friction angle change at different water content. The results show that high permeability coefficient and strong capillary are main factors to increase the water content, and the influence of capillary rising is greater than that of rainfall infiltration. The strength characteristic of silt soil is similar to the character of non-cohesive soil in low water content and that of clay in high water content. If the water content is greater than optimum water content, the elastic modulus and cohesion of silt shall decay obviously. Friction angle decreases dramatically as well, when the soil is saturated.

Abstract: It is important to understand soil hydraulic properties in order to predict the movement of water and solutes such as pollutants. To this end, 55 soil samples were collected from different areas of the Nanxiaohegou basin and used to generate soil-water characteristic curves. These were then fitted using the power-, exponential-, and logarithmic versions of the Gardner model; the logarithmic model yielded the best fit overall. The logarithmic model was further simplified to yield a one-parameter model for estimating the soil-water characteristic curve within the basin, and it was demonstrated that the value of the single parameter is dependent on the topography and usage of the land.

Abstract: This research investigates the relationship between optical density and liquid saturations in unsaturated sand using multispectral image analysis technique. The tested liquids are water, diesel, and parafin liquid. The experiments are performed on two-fluid phase systems (water-air, diesel-air, and parafin liquid-air) and three-fluid phase systems (diesel-water-air and parafin liquid-water-air). Water is dyed with Brilliant Blue FCF, whereas diesel and parafin liquid are dyed with Red Sudan III. Using consumer-grade digital cameras, two images of sand specimens with various liquid saturations are taken with two different band-pass filters. The analysis results show that, for the sand and investigated fluids, the optical density defined for the reflected luminous intensity is a linear function of the degrees of fluid saturation for each spectral band and for any two- and three-fluid phase systems.

Abstract: The rigidity and density changes of foundation soil were studied in this paper ,as well as the change rules of earthquake wave spread effect and site dynamic characters,through comprehensive wave velocity test and the computer simulation,in which the ground water level change was taken into consideration . According to the engineering examples, the effect of the fluctuation of underground water level on the site predominant period is analyzed.

Abstract: In order to research shrinkage of hole-wall and plastic region around hole-wall of bored pile in drilling process, a porous analysis model was built, and drilling process of bored pile, under dry excavation technology and hydraulic excavation technology, were simulated by element birth and death feature in ADINA software. Numerical analysis results show that to seasonal frozen ground in the west of China, dry excavation technology is not appropriate, consolidation settlement caused by drilling is small and can be taken into no consideration in design, major problem in hydraulic excavation technology is shrinkage of hole-wall, which mainly influenced by density of slurry and excavation depth one time.

Abstract: Incremental method, as one of the practical calculation methods in retaining structure design of foundation pit, has been widely used. When incremental method is applied, the earth pressure, acting on the retaining structure on each incremental step, is considered as static earth pressure. Actually, the state of earth pressure changes constantly with the increase of soil displacement in the process of excavation. This paper introduces the relation of displacement and earth pressure based on the soil stress-strain state, and makes corrections for the earth pressure of the incremental method. By comparing with the measured data of the engineering, the calculation results, which consider earth pressure modification, are in good line with the practical engineering condition. The method in this paper can provide certain reference for related engineering design.