Applied Mechanics and Materials Vols. 353-356

Abstract: Referring to the previous shearing model tests on intermittence jointed rock mass, DDARF method was adopted to conduct the corresponding numerical simulation. It could be concluded from the cracking failure phenomena that the results of the numerical simulation and the tests were in good agreement. Then the intermittence joints were arranged as en echelon and different cracking failure phenomena, peak shear strengths and strain-stress relationships were also obtained.

Abstract: In long term practice of rock engineering, the strength and failure rules based on classical elasticity and plasticity theory is always dominated in judging the safety and stability of practical engineering. However, stress-strain relationship is only a certain state of rock mass in loading process, and it is hard to give an accurate evaluation for the engineers especially due to the diversity and divergence of mechanical parameters. For actual loading process of rock mass is always companied with energy dissipation and releasing, in this paper, we put emphasis on the ratio of dissipated energy to overall absorbed energy in the cyclic loading process. From this point of view, three important sections are gained as follows: a) condensing section: the ratio is higher due to the closing effect of original cracks; b): elastic section: the value of ratio sharply goes down and is nearly a constant in the elastic section; c) approaching to failure section: this is a section closely to the failure because the newly cracks occurs ceaselessly and the ratio value becomes higher.

Abstract: The Qinghai-Tibet direct-current transmission project crosses the high-altitude permafrost region of the Qinghai-Tibet plateau. The permafrost foundation is characterized by being poor in thermal stability, rich in underground ice, very sensitive to climate warming, and strong in water-thermal activity. The foundation of the transmit electricity engineering therefore faces great challenges including tower foundation type selection and design, permafrost protection in the process of foundation construction and long-term stability. Based on an analysis of the geological engineering conditions and principal geological engineering problems of the project, a study is carried out on the design and construction problems of the transmission tower foundations in the permafrost region, the systematic analysis is also made regarding the main solutions to these problems with consideration of tower foundations long-term stability. This study will provide a theoretical basis and technical guide for design and construction of transmission lines in the permafrost region, and a reference for construction of transmission line projects in similar regions in China or even in the world.

Abstract: Equation of three dimensional stress, seepage pressure and permeability coefficient was obtained by theoretical analysis. Applying the true triaxial rock testing system of coupled stress-seepage, seepage test of granite sample with prefabricated single fracture was made under three dimensional coupled stress-seepage. The results show that three dimensional stress have the inhibition effect on single fracture seepage, and the normal main stress, having the leading role, obviously influences the permeability coefficient; seepage pressure has the promote effect on single fracture seepage, resisting the normal main stress. Fitting formula of granite permeability coefficient was gained under coupled stress-seepage which indicated the exponential relationship between permeability coefficient and three dimensional stress and seepage pressure.

Abstract: The effects on rigid pile composite foundation caused by lateral unloading in horizontal direction are studied in this paper. Considering the excavation of neighborhood deep foundation ditch, a calculation model for the composite foundation is proposed and the theoretical formula of pile deformation is given. Furthermore, the formula of bending moment of the pile in the composite foundation is deduced in this paper.

Abstract: Through field static load test and pile shaft axial force test, field testing study is conducted on bearing behavior of NAKS-construction-method belled large-diameter PHC pipe pile; besides, the test result is compared with that of hammering-method PHC pipe pile and bored pile with same pile length and diameter under the same site condition. The result shows that the ultimate bearing capacity of NAKS-construction-method belled large-diameter PHC pipe pile is slightly inferior to hammering-method PHC pipe pile but obviously superior to that of bored pile. Compared with traditional hammering-method pipe pile, the pile side resistance of NAKS-construction-method belled pipe pile is smaller; however, the higher toe resistance will give better play to bearing capacity of bearing stratum of pile toe; moreover, it is found that under the action of ultimate load and failure load, the maximum settlement and final settlement of NAKS-construction-method belled pipe pile tip are obviously lower than that of other test piles, which is conductive to lessening foundation settlement of upper structure.

Abstract: Based on the limit equilibrium theory and the failure model of the soil nailing structure, used the circular slice method and the geometric relationship of circular sliding surface with the center of the circle to derive the stability coefficient formula. The most dangerous slip surface was searched by genetic algorithm. To establish the reliability analysis function through the stability coefficient formula. Finally, the reliability calculation of engineering examples, compared the results with the Monte Carlo method, the reliability analysis method was reasonable and valid.

Abstract: The Modified strain triaxial apparatus is used to reveal the deformation mechanism of humid laterite. Taking into account the impact of different factors on the laterite wet deformation, the test designs different confining pressures, different degrees of compaction, different wet partial stress levels, to analyze the multi-angle of wet deformation of laterite. Humid laterites parameters are studied in different test conditions. The relationships of principal stress differences, axial strain, bulk strain, radial strain are analyzed.

Abstract: Main research object of this article is marine dredging silt in Tianjin Binhai region. It discusses natural settlement rule of dredged silt with different moisture content in Tianjin Binhai region through conducting indoor natural settlement model experiment to dredged silt of different moisture content. The results indicated that natural settlement of dredged silt in Tianjin Binhai region can be divided into three stages: the first stage is quick subsidence stage within 4-5 hours at the start of the experiment, during which settlement rate of dredged silt is fast and settlement volume is large; the second stage is natural deposition transition section stage within 2 days after the experiment, when settlement rate of dredged silt starts slow down but settlement volume is obvious; the third stage is dead-weight consolidation settlement stage of slow settlement after 2 days since the start of the experiment, in which settlement rate of dredged silt is slow and settlement volume is less. Settlement of Dredged silt in Tianjin Binhai region is greatly influenced by its initial moisture content. The higher the initial moisture content is the faster initial settlement rate of dredged silt will be and so is the final settlement volume of dredged silt.

Abstract: The soil-water characteristic curve (SWCC) reflects water storage capacity, Measuring it accurately is important in engineering. This paper concluded main factors of SWCC, measured soil-water characteristic of loess under conditions of different dry densities, the curve of volume water content, saturation and matric suction were presented, the curves showed similar change trend, saturation mainly determined the matric suction when matric suction was small.