Applied Mechanics and Materials Vols. 295-298

Abstract: One of the main content of the environmental geotechnical engineering is engineering disaster problem brought by environmental change, the most basic problem is the influence of occurrence environment on the mechanical properties of rock. The water-saturated and freeze-thaw cycling experiment were conducted for dried shale under the open system, then carried out the mechanical properties experiment on dry and water-saturated state and on certain times of freeze-thaw cycles, the characteristics of the water softening, freeze-thaw damage deterioration, deformation and failure for shale were studied systematically. It is shown that the moisture has an important impact on mechanical effect of shale. With the increasing of the freeze-thaw cycles, the elastic modulus and strength of the shale reduce significantly, then approach stably after experiencing a certain number of freeze-thaw cycles, while the ultimate strain is increasing continuously. The engineering problems brought by environmental change must be solved from moisture and temperature in geotechnical engineering in cold regions.

Abstract: Using Magellan Seamount samples in the Pacific area to carry out the REE chemical analysis and microscopic descript,this paper analyze the content of REE between the basement rock and co-rich crust, distribution characteristics, distribution pattern.The results show that: the three layers samples contain high value, total quantity is about 1000×10-6, compared with normal deep sea sediments, foraminiferal nuclear shell and sea water content of rare earth elements10 ~ 100 times; Basement and co-rich crust have shown consistent in distrubution mode, REE content is perfectly high, co-rich crust of REE is mainly controlled by overlying seawater on the rock points erosion. volcanic eruption, ocean floor basalt weathering and biological chemical deposition on the formation of the crust also has certain influence. REE as a huge resource is superior to exploit, The comprehensive development and utilization of mineral resources provided good premise, it is possible to createREE resource utilization of the new way.

Abstract: Water fracturing is vast applied in low permeability oil-gas filed, and gains extremely economic benefit. But not all low permeability reservoirs are suitable for water fracturing. This paper analyzed the fracture deformation characteristics and closed form in complex stress state, the fracture surface roughness and shear-slip caused the fracture surface couldn’t be completely meshed, there was residual space. Based on the characteristics, the self-support fracture combination and conductivity test method were established. The non-dimensional conductivity as the evaluation index, the water fracturing reservoir screening method was established.

Abstract: The seepage field of tailings pond is analyzed. Based on the result distribution of hydraulic head and velocity in the dam body, seismic analysis is carried out for the tailings pond in steady flow state. Three seismic waves are input and the safety factors of dam under seismic action are also achieved. The results show that the safety factor will decrease 0.3~0.4 with the seismic intensity increase one degree. The results provide some information on seepage and dynamic stability evaluation of tailings dam.

Abstract: The long-term ground severe deformation and destruction induced by open pit and underground mining can badly affect the safety of surrounding environment. This problem is different from ground deformation and destruction induced by single mining. Based on chronological relationship between two kinds of mining and its corresponding deformation law under a practical engineering, the main reasons for long-term deformation and the deformation mechanism were revealed in this paper. Starting with the displacement mechanism, a method of horizontal movement coefficient was put forward to distinguish the movement property. Therefore, the impacts on two components of displacement vector can be distinguished, and then the basis for the proper analysis of ground deformation would be reached. At the same time, the ground deformation zone and the failure zone caused by subsequent open pit mining would be predicted, and the range of the failure zone would be gotten, providing a basis for safety decision.

Abstract: Compared to the other methods of stress measurement, classical hydraulic fracturing (HF) technique is a relatively convenient and economic method to determine stress and interpret the test results. However the HF method can only obtain the local dimensional (2D) stress of the plane perpendicular to the axis of test holes. In this paper, two HF measurement campaigns applied in two hydroelectric projects in China have been presented to describe how to obtain the three dimensional (3D) stress from three different direction shallow boreholes in the same section by HF, and how to carry out the back analysis of a large scale area stress field based on the test results.

Abstract: According to comprehensive researches on indicators of lithology，indicators of primary sedimentary structures，bioclasts and matrix, summarize sedimentary characteristics and origin for sandbody in the Zhujiang formation of the Well LW3-1-1. The main rock types are mid-coarse grained sandstone with heavy coloured mudstone at its top and bottom，followed by very coarse grained sandstone with fine gravel occurs locally. It is showed that the sandstones are well sorted with very low content of mud, and possess high compositional maturity and textural maturity. Massive bedding, typical inverse graded bedding and inverse-normal graded bedding occur in the sandstones. So in general, it is a set of sedimentation of grain flow and density-modified grain flow.

Abstract: Gravels and natural fractures in glutenite formation have significant impacts on fluid loss when hydraulic fracturing is conducted. Matrix permeability and porosity were computed through Kozeny-Carman equation when gravels contents and size are known. Then a pebbly dual permeability dual porosity model was used to quantitatively evaluate the fracturing fluids loss in glutenite formation. Filtration rate curves could be plotted from the pressure distribution function which was obtained through orthogonal transformation method. Different gravels contents and multi-size-gravels were taken into accounts in this paper. The results show that both filtration rates in matrix and natural fractures decrease with increasing gravels content in matrix; and the filtration rate in matrix decrease much more. Impacts of gravel content are more significant than impacts of gravel size. Natural fractures have much more significant impacts than gravels.

Abstract: Dynamic shear modulus ratios and damping ratios of soil are the parameter of indicating dynamic nonlinearity of soil, and the necessary parameter of seismic site analysis. The 372 pairs of soil samples’ dynamic nonlinear parameters, which were tested by dynamic tri-axial tests in about 40 the seismic safety evaluation reports of ocean oil platforms in the Bohai Sea, were collected and corrected. The dynamic shear modulus ratios and the damping ratios of various soil types with different depth in the Bohai seafloor were calculated and their statistical mean values were obtained. The statistical mean values are reasonable and are the important supplements in case that the tested soil samples are not enough in the Bohai Sea sites.

Abstract: An outburst of coal and gas is a major hazard in underground coal mining. It occurs when certain conditions of coal stress, strength and gassiness are met. Based mainly on field observations related to the conditions, a number of indices are used in prediction of the outburst. Some of the indices are considered to be inadequate, inappropriate or impractical in some coal seam conditions. Significant progresses have been made in development of the technologies over the last few years. One of the major achievements is an analytical method in determination of an outburst threshold value of the gas content in a coal seam. The method combines field measurements and numerical modelling. The method is illustrated in this paper in a case study for determination of the outburst threshold value of gas content for a coal seam.