Applied Mechanics and Materials Vols. 204-208

Abstract: The mechanical behavior of rock interior creep fracture evolution and the state are difficult to observe. Combined with the laboratory rock compressive-creep test, the uniaxial creep numerical test based on FLAC3D was carried out. The different positions of the model displacement, stress, strain and damage zone were analyzed under different loading. The mechanical behavior of evolution process and characteristics of rock creep fracture were revealed under the different loading. The results show that: the data of numerical simulation and laboratory test are identical by comparing with laboratory test, and numerical test on simulated rock creep mechanical behavior evolution and methods is feasible and effective. It is a new method that can improve laboratory test of the microscopic creep, provide basis for evaluation of engineering rock mass stability too.

Abstract: This study is analyzed by numerical analysis using finite element method program of Plaxis-3D Tunnel at Kaohsiung Science Park in Taiwan. It probes the risk of tunneling procedure adopting pipe jacking construction (PJC) with man–made excavation. The main parameters of numerical calculation in this research include advancement size, soil improvement ratio and void contraction ratio, etc. Those parameters are calculated to displacement and stress distribution and we get ground movement, settlement at crown and heave at invert of tunnel excavation to assess the security. This study finds that it is safe by excavation using PJC with man-made while the gap has to be less than 38mm. Actually, the gap is 100 ~ 150mm under PJC with man-made, and it will result in high risk. Therefore, the PJC with shield has more security than other methods through monitoring ground settlement.

Abstract: In this paper, marine sediments soft soil of Beigangchi wharf in Tianjin port was scanned by Computer Tomography(CT) in different load during uniaxial consolidation experiment. The CT images were analyzed to research on the relationship between the microcosmic characteristics of Marine deposits soil and it’s compression in Tianjin areas. The results show that: with the increase of the pressure loading, the average grey value of the CT images increases gradually, which illustrates that soil samples are compacted and the density increases. The variance decreasing of CT image grey value indicates that the soil sample get more evenly. Soft soil of Beigangchi wharf in Tianjin port has high compressibility through the changes of grey compression coefficient. This paper can be referenced for the research of the structure changes of the soil sample consolidation process.

Abstract: According to the experiments study of sulfuric acid saline soil, the formula of compression coefficient with the changes of moisture content, salt content, initial dry density and temperature is presented, and the interaction law between the various influencing factors on sulfuric acid saline soil compression are analyzed in the paper.

Abstract: Test equipments were designed and manufactured for producing moisture migration in unsaturated loess under freezing effect. The results showed that both the amount of freezing-thawing cycles and initial water content of soil samples affect the process of moisture migration. As the freezing front advanced in the sample, the water content in the unfrozen part significantly reduced and the water content in the freezing part significantly increased, with the maximum water content at the freezing front. Comparing to the moisture migration in the unfrozen part, the moisture migration to the freezing front in the freezing part was relatively slow. For soil samples with higher initial water content, the increment of water content at the freezing front was higher and sometimes ice could be formed. During a certain amount of freezing-thawing cycles, the water content at the freezing front kept increasing. However, as the amount of freezing-thawing cycles continued increasing, the freezing front started to move to the part with negative temperature and the maximum water content appears at the end with the lowest temperature.

Abstract: Strong earthquake ground motion leads to residual displacements of gravity retaining walls. Since large deformation occurs in foundation soil, nonlinear mechanical behavior should not be neglected in numerical modeling. The inversion methodology in geophysics is borrowed here to study the nonlinearity, i.e. the variation of shear modulus and damping ratio with the increase of shear strain of soil. A simplified model for the seismic displacement of retaining walls is combined with a genetic algorithm for the inversion. The dynamic shear modulus and damping ratio curves, representing the nonlinear property of foundation soil in a centrifuge test for gravity retaining walls, is obtained by the use of an inversion scheme. The result indicates that, for low level of shear strain, the shear modulus is larger than that used in the literature, implying that the model ground may be stiffer than expectation. For high level of shear strain, the inverted damping ratio is larger than the conventional one, which has efficiently suppressed an overestimation of seismic displacements. It is also displayed that the inversion method is an effective way to obtain quantitatively the dynamic nonlinearity of foundation soil of gravity retaining walls.

Abstract: The laboratory landslide test device of three part constituting by the model slotk and the catchment sink and rainfall system is developed according to test requirements, and it carried out to research calibration test of rainfall and correction of rainfall for rainfall systems under laboratory conditions. The calibration results of rainfall shown that the indoor rainfall increases linearly with time if the opening of the water-tap is reasonably controlled and that can ensure stability of the supplying water of the laboratory landslide test. The correction results of rainfall shown that, according to the energy balance method and volume method, the indoor rainfall can be converted the actual rainfall by the energy reduced coefficient in the indoor rainfall conditions and the actual rainfall conditions of the slope, and that ensure requirements of rainfall of laboratory landslide tests corresponding to the actual rainfall.The energy reduced coefficient is determined by landing speed of indoor raindrop and end speed of actual raindrop.

Abstract: Based on the characteristics of frequent ground subsidence events caused by groundwater level fluctuation in coastal cities in China, the effects of groundwater level fluctuation and building load change on the strength and deformation of silt is simulated by laboratory experiments in studying on the quaternary sedimentary silt in Shanghai. It has summarized the law of the strength and deformation of silt foundation and its inherent varying mechanism through these data. The methodology and result of this research, which can be used as a reference for similar engineering and urban ground subsidence prevetion.

Abstract: High fill culverts have been widely used in expressway in mountain area and problems of culverts frequently take place because of improper design including some earth-pressure calculated values conservatively or culvert type selection irrationally. FEM numerical simulation was carried out to investigate the stress state of the culvert fill. The effect of four influences on the stress state of high-filled culvert is discussed. The research results show that culvert structure type influences earth pressure distribution that arch culvert is different to slab and box culvert. Earth pressure values when boundary slope is 1:0.35 are all larger than slope 1:0. Due to arch effect and stress distributed secondly, nonlinear increased amplitude of earth pressure is reduced with fill heightening. Earth pressure of culvert top and side decreased along with culvert side wall thickness increment. The research can give some references on the design correctly.

Abstract: Daomakan slope, a typical ancient slope by Jingsha River, locates in Xiangjiaba Reservoir. With the rising of water level of Xiangjiaba Reservoir, Daomakan slope might pose threaten to the reservoir. Based on the detailed field investigation, the author firstly proves that Daomakan slope is an ancient landslide by the following evidences: a 1.5 meters cracked layer was found at the front of the landslide and a very deep shearing scratch appeared on the bedrock surface. Meanwhile ,the evidences above can be used to speculate that the strong earthquake is the main cause in triggering the landslide. According to the triggering and sliding process, stability analysis is conducted from an engineering geological perspective. The method adopted in this paper is suitable for field investigation, and provides a certain reference value on the ancient seismic landslides stability analysis in Xiangjiaba Reservoir area.