Advanced Materials Research Vols. 446-449

Abstract: Phenyl isocyanate is used to react with 3-methyl-1,3-butanediol at different temperatures. Dimethylformamide is used as solvent. In-situ FT-IR is used to monitor the reaction to work out rate constant, Arrhenius equation and Eyring equation. The urethane reaction has been found to be a second order reaction, and the rate constant seems different between initial stage and final stage. The activation energy (E_a), activation enthalpy (ΔH) and activation entropy (ΔS) for the urethane reaction of tertiary hydroxyl group are calculated out, which are 75.2 kJ•mol^-1, 72.4 kJ•mol^-1 and -44.8 J•mol^-1•k^-1, respectively. They are very useful to reveal the reaction mechanism.

Abstract: Saturated and unsaturated seepage analysises are given for Dashiban Landslide applied a particular rainfall type, The impaction of typical rainfall on the stability of landslide is discussed, and further research foundation is layed.

Abstract: Based on unified strength theory, an upper bound solution for bearing capacity of foundation is established considering the strength of soil above the basement by using Prandtl slip model. The proposed method could be degenerated to classical slip-line method in some certain situations. A series of results could be presented by means of changing the parameters of unified strength theory. The results obtained by this proposed method are greater than those by Terzaghi method, which is mainly because the positive effects of soil strength above foundation base. Since unified strength theory could be simplified to Mohr-Coulomb strength theory in a certain situation, the results are close to those obtained by Meyerhof method. This proposed solution can consider the effects of intermediate principal stress so that we can make full use of the potential capacity of soil, which is a rigorous upper-bound solution. Other solutions are special cases of this proposed solution.

Abstract: For a general slice, force and moment equilibrium equations are developed, the recurrence equations of inter-slice force and inter-slice moment are derived, the general formulation based on rigorous equilibrium to solve the factor of safety is studied, hence, the theoretical framework of rigorous method of general slice is developed, rigorous method of vertical slice is a special case of it. Analyzing the applicability of Sarma’s method, two new inter-slice shear force equations are presented based on the compatible relationship among slice’s displacements by leading in the scaling parameter λ and inter-slice force function f(x),hey make the relationship between the inter-slice shear forces and slip surface geometry clear, and indicate that the reduction factor for shear strength along inter-slice boundaries varies from one boundary to the next depending on the geometry of the slices and the slip surface. The rigorous methods of general slice can be developed based on the modified inter-slice shear force equations, they think that the reduction factor for shear strength along inter-slice boundary is different from that for shear strength along slip surface. The example analysis indicates that the proposed new methods work better than Sarma’s method, the reasonable value of safety factor can be obtained by using them. Even if the shape of slice is varied, the proposed new methods can also give consistent values of safety factor and ensure that the iteration is stably convergent.

Abstract: With the foundation pit of south air shaft nearby Qiantang River, Subway No.1, Hangzhou, Zhejiang province as an example, the interaction between pumping wells and underground concrete wall, together with the soft curtain formed by recharging wells are simulated with numerical method. The results indicate that the proper position of filter tube of pumping well to underground concrete wall can reduce the drawdown outside pit, and the drawdown outside pit can be reduced by recharging curtain.

Abstract: Grouted rockbolts are widely used in tunneling excavation. However, the rockbolt design is still basically empirical, the mechanical behavior of grouted rockbolts, especially the interfacial behavior, has never been studied systematically. First of all, a tri-linear bond slip model is proposed for modeling the rockbolt interfacial behavior. Then analytical solutions to grouted rockbolt are presented on the basis of a tri-linear bond-slip model. Finally, a numerical model using Abaqus program to simulate the tunnel rockbolt is proposed. This model uses cohesive elements to simulate debonding along the anchorage interfaces, meanwhile, tabular damage variable is obtained on the basis of the damage evolution law in order to correspond with the tri-linear material model. The developed model was validated by monitored data. It was found that the model was capable of predicting accurately the interfacial shear stress distribution, load on the bolt as well as the rock movements. Therefore, this model can be used to optimize the control parameters of grouted rockbolts.

Abstract: Based on the monitoring data of the deep foundation pit, established an adjacent deep foundation pit safety risk fuzzy synthetic evaluation model, and then determine safety grades , using the method to evaluate the safety of the environment surrounding the foundation pit. Practice proves that the method can reflect the risk condition of the pit, and provided a new way to check the security of the pit.

Abstract: Affected by a group of underground chambers and gobs of working faces, the track sub-inclined shaft of 430 mining area in Geting coal mine, which crosses coal seam and faults repetitively, lies in high and complex stress environment. Based on geostress results measured in the field, FLAC3D numerical simulation software was used to simulate the regional geostress in the area near the roadway, referring to the impact of the gobs and chambers. And the stress variation law along the roadway was given at last. Then the roadway roof structure zone chart was drawn according to the detection results with the rock video detection recorder. Finally, stability of different sections of the roadway and the support advice corresponding to each section was gained. The results show that comprehensive consideration of geostress variation law and surrounding rock structure is necessary in the stability classification and the support of roadways. The research methods and ideas given in this paper is feasible.

Abstract: The marine cofferdams of the littoral new town in Lianyungang were constructed with geotextile bags filled with solidified soil and the soft ground under the cofferdams was treated by under water vacuum preloading method. The dimension of the cofferdams was reduced while the foundation kept stable. And the cofferdams were configurated with the geotextile bags filled with solidified soil, the silt clay was utilized adequately, the sand stone resource was saved and protected, the obvious effect was achieved. This method can be promoted in construction of marine cofferdams.

Abstract: Structure stability of bedded rock slopes are determined by material characteristic of rock blocks and geometrical non-linearity of the discontinuous interfaces between the rock blocks. Different dip angle of the similar slopes are with different safety factors. In this paper, the discrete element method is adopted for calculation and the common plane method for contact surface searched, and the mathematical model is reviewed. Both states of calculation mode are adopted to analysis and compare, one considers the material elastic-plasticity of blocks of rock slope only, in the contrast, the other introduces the geometrical non-linearity to calculation model and the safety factor is less than the counterpart of first state.