Based on the upper bound limit analysis theorem and the shear strength reduction technique, the equation for expressing critical limit-equilibrium state was employed to define the safety factor of a given slope and it...Based on the upper bound limit analysis theorem and the shear strength reduction technique, the equation for expressing critical limit-equilibrium state was employed to define the safety factor of a given slope and its corresponding critical failure mechanism by means of the kinematical approach of limit analysis theory. The nonlinear shear strength parameters were treated as variable parameters and a kinematically admissible failure mechanism was considered for calculation schemes. The iterative optimization method was adopted to obtain the safety factors. Case study and comparative analysis show that solutions presented here agree with available predictions when nonlinear criterion reduces to linear criterion, and the validity of present method could be illuminated. From the numerical results, it can also be seen that nonlinear parameter rn, slope foot gradient ,β, height of slope H, slope top gradient a and soil bulk density γ have significant effects on the safety factor of the slope.展开更多
In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovi...In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.展开更多
The growth of Maesopsis under the influence of various geomorphic surfaces was followed within a period of 70 months. Young plants of two months old were transplanted into 70 × 70 × 70 cm holes under natural...The growth of Maesopsis under the influence of various geomorphic surfaces was followed within a period of 70 months. Young plants of two months old were transplanted into 70 × 70 × 70 cm holes under natural conditions (no inputs such as manure and other amendments). A randomized complete block design was set up for the experiment, alongside a control, and growth parameters followed (height and collar circumference). Three blocks with different geomorphic surfaces were put in place for the experiment (upper slope or block 1, middle slope or block 2 and foot slope or block 3). Results of the experiment indicated that geomorphic surface had a significant effect on height but not on collar circumference. Plant height increased progressively from upper slope to foot slope;less tall trees were found at the upper slope, while the tallest trees were found at the foot slope. After 70 months, maximum average height attained by plants for the experiment was 1228.3 cm, observed in block 3 (foot slope), significant at 0.05 confidence level with respect to geomorphic surface. In blocks 1 and 2 (upper slope and middle slope), maximum average heights attained were 798.5 and 937.5 cm, respectively and were shown to be statistically equal at 0.05 confidence level. Geomorphic surface had no effect on collar circumference. Maximum average collar circumferences attained after 70 months were 62.8 cm (observed at the upper slope), 61.3 cm (observed at the middle slope) and 76.3 cm (observed at the foot slope) and the various collar circumferences were shown to be statistically the same at 0.05 confidence level. For the control, maximum height attained after 70 months was 1240 cm (observed at the foot slope). At the upper slope and middle slope, maximum average heights were respectively, 800 cm and 905 cm, and were statistically equal at the 0.05 confidence level but different from the foot slope value of 1240 cm. Maximum average collar circumference was observed at the foot slope (76.3 cm), while circumferences of 62.8 cm and 61.3 c展开更多
Based on the limit analysis upper bound method,a new model of soil slope collapse has been proposed which consists of two rigid block zones and a plastic shear zone.Soil slope was induced failure by coupling effect of...Based on the limit analysis upper bound method,a new model of soil slope collapse has been proposed which consists of two rigid block zones and a plastic shear zone.Soil slope was induced failure by coupling effect of rainfall and earthquake,and these blocks were also incorporated horizontal earthquake force and vertical gravitate.The velocities and forces were analyzed in three blocks,and the expression of velocity discontinuities was obtained by the principle of incompressibility.The external force work for the blocks,the internal energy of the plastic shear zone and the velocity discontinuous were solved.The present stability ratios are compared to the prevenient research,which shows the superiority of the mechanism and rationality of the analysis.The critical height of the soil slope can provide theoretical basis for slope support and design.展开更多
Comparing with the homogeneous slope, the nonhomogeneous slope has more significance in practice. The main purpose of the present study is to provide a preliminary idea that how the nonhomogeneity influences the stabi...Comparing with the homogeneous slope, the nonhomogeneous slope has more significance in practice. The main purpose of the present study is to provide a preliminary idea that how the nonhomogeneity influences the stability of slopes under four different water drawdown regimes. Two typical categories of nonhomogeneity, identified as layered profile and strength increasing with depth profile, are included in the paper, and a nonhomogeneity coefficient is defined to quantify the degree of soil properties nonhomogeneity. With a modified discretization technique, the safety factors of nonhomogeneous slopes are calculated. On this basis, the variation of safety factor with the nonhomogeneity coefficient of friction angle and the water table level are investigated. In the present example, safety factor correlates linearly with friction angle nonhomogeneity coefficient from a whole view and the influences of the water table level on safety factor is basically similar with that in homogeneous condition.展开更多
基金Project(2006318802111) supported by West Traffic Construction Science and Technology of ChinaProject(2008yb004) supported by Excellent Doctorate Dissertations of Central South University, China Project(2008G032-3) supported by Key Item of Science and Technology Research of Railway Ministry of China
文摘Based on the upper bound limit analysis theorem and the shear strength reduction technique, the equation for expressing critical limit-equilibrium state was employed to define the safety factor of a given slope and its corresponding critical failure mechanism by means of the kinematical approach of limit analysis theory. The nonlinear shear strength parameters were treated as variable parameters and a kinematically admissible failure mechanism was considered for calculation schemes. The iterative optimization method was adopted to obtain the safety factors. Case study and comparative analysis show that solutions presented here agree with available predictions when nonlinear criterion reduces to linear criterion, and the validity of present method could be illuminated. From the numerical results, it can also be seen that nonlinear parameter rn, slope foot gradient ,β, height of slope H, slope top gradient a and soil bulk density γ have significant effects on the safety factor of the slope.
基金Project(2008ZX05004-004)supported by the State Key Scientific Research Programs,ChinaProject(SZD0414)supported by the Sichuan Province Key Discipline Construction Project,ChinaProject(KZCX2-YW-Q05-01)supported by the Chinese Academy of Sciences Innovation Engineering Directional Project
文摘In order to reveal the relationship between the penecontemporaneous karstification and sedimentary microtopography in sequence stratigraphy,the sequence stratigraphic framework of Lianglitage formation in Upper Ordovician is studied according to the well drilling,logging,geophysical data,detailed observations of core and the paleontology.The Lianglitage formation belongs to the sequence Ⅳ of Ordovician.The second member of Lianglitage formation is prograde sedimentation in highstand systems tract,and is favorable for developing reef flat.The development scale and thickness of reef flat are controlled by the variation of secondary sea level.The types and characteristics of karst in the highstand systems tract show that the late highstand systems tract is dissolved and cemented by the meteoric fresh water and mixed water.Penecontemporaneous karstification is developed at the top of parasequence and high place of geomorphology.Atmospheric diagenetic lens is formed.The developing regulations and controlling factors of penecontemporaneous karstification can provide new clues to the prediction and exploration of favorable reservoir in this area.
文摘The growth of Maesopsis under the influence of various geomorphic surfaces was followed within a period of 70 months. Young plants of two months old were transplanted into 70 × 70 × 70 cm holes under natural conditions (no inputs such as manure and other amendments). A randomized complete block design was set up for the experiment, alongside a control, and growth parameters followed (height and collar circumference). Three blocks with different geomorphic surfaces were put in place for the experiment (upper slope or block 1, middle slope or block 2 and foot slope or block 3). Results of the experiment indicated that geomorphic surface had a significant effect on height but not on collar circumference. Plant height increased progressively from upper slope to foot slope;less tall trees were found at the upper slope, while the tallest trees were found at the foot slope. After 70 months, maximum average height attained by plants for the experiment was 1228.3 cm, observed in block 3 (foot slope), significant at 0.05 confidence level with respect to geomorphic surface. In blocks 1 and 2 (upper slope and middle slope), maximum average heights attained were 798.5 and 937.5 cm, respectively and were shown to be statistically equal at 0.05 confidence level. Geomorphic surface had no effect on collar circumference. Maximum average collar circumferences attained after 70 months were 62.8 cm (observed at the upper slope), 61.3 cm (observed at the middle slope) and 76.3 cm (observed at the foot slope) and the various collar circumferences were shown to be statistically the same at 0.05 confidence level. For the control, maximum height attained after 70 months was 1240 cm (observed at the foot slope). At the upper slope and middle slope, maximum average heights were respectively, 800 cm and 905 cm, and were statistically equal at the 0.05 confidence level but different from the foot slope value of 1240 cm. Maximum average collar circumference was observed at the foot slope (76.3 cm), while circumferences of 62.8 cm and 61.3 c
基金National Natural Science Foundation of China(No.51478444)
文摘Based on the limit analysis upper bound method,a new model of soil slope collapse has been proposed which consists of two rigid block zones and a plastic shear zone.Soil slope was induced failure by coupling effect of rainfall and earthquake,and these blocks were also incorporated horizontal earthquake force and vertical gravitate.The velocities and forces were analyzed in three blocks,and the expression of velocity discontinuities was obtained by the principle of incompressibility.The external force work for the blocks,the internal energy of the plastic shear zone and the velocity discontinuous were solved.The present stability ratios are compared to the prevenient research,which shows the superiority of the mechanism and rationality of the analysis.The critical height of the soil slope can provide theoretical basis for slope support and design.
基金Project(51408180)supported by the National Natural Science Foundation of China
文摘Comparing with the homogeneous slope, the nonhomogeneous slope has more significance in practice. The main purpose of the present study is to provide a preliminary idea that how the nonhomogeneity influences the stability of slopes under four different water drawdown regimes. Two typical categories of nonhomogeneity, identified as layered profile and strength increasing with depth profile, are included in the paper, and a nonhomogeneity coefficient is defined to quantify the degree of soil properties nonhomogeneity. With a modified discretization technique, the safety factors of nonhomogeneous slopes are calculated. On this basis, the variation of safety factor with the nonhomogeneity coefficient of friction angle and the water table level are investigated. In the present example, safety factor correlates linearly with friction angle nonhomogeneity coefficient from a whole view and the influences of the water table level on safety factor is basically similar with that in homogeneous condition.
