Applied Mechanics and Materials Vols. 501-504

Abstract: The mechanized level of coal mining work is developing rapidly, the roadheader and shearer are the most important equipments. The conical pick acts on coal or rock directly, and its design and selection play an important role in the operational reliability of these equipments. However, the cutting force is the basis to design and select conical pick [1, . At home and abroad, many researchers attempted to establish the theoretical models for calculating the peak cutting force of conical picks. Evans used the maximum tensile criterion to set up the theoretical model for conical pick, and the model was widely used in the design of roadheader, shearer and so on in Europe and America [. Goktan et al. developed the presented model based on Evans theoretical model, and they given the modified model [. Okan et al. adopted the finite element method and the discrete element method to simulate the rock or coal cutting process to predicate the cutting force [. As mentioned above, the theoretical model is easy to calculate the cutting force, but the results have big difference with the experimental result due to simplify the relations between the cutting force and parameters. The numerical method is difficult to predicate the cutting force accurately, because the influence of rock or coal constitutive model, element failure criterion and boundary condition on cutting process. Therefore, the RBF Neural Network for predicating the cutting force was established base on a large amount experimental data in this paper. The aim is to predicate the cutting force accurately and reliably, and provide some basis to design and select the concial pick.

Abstract: Through the Statnamic load test on working bored pile, the displacement of pile top and the distributing of axis force along the bored pile were brought forward and two methods were used for interpretation the test result. The bearing capacity, axial force, shaft friction and pile toe resistance of pile were all illustrated. The result show that the Statnamic load test method can check the pile capacity quite easily, it is quite difficult to test the ultimate pile capacity.

Abstract: With the background of the foundation treatment engineering of a river dam in a reservoir, the thesis introduced the site experiments for soft soil foundation reinforced by vibro-replacement stone piles. Moreover, the study had also conducted inspection and analysis of the reinforcing effect of the composite foundation being reinforced by vibro-replacement stone piles including the inspections like the stress ratio between the vibro-replacement stone pile and earth among pile and the ratio between the vibro-replacement stone pile and the pile earth. Finally, the study came to below results after comprehensively considering the results of the heavy dynamic penetration test, standard penetration test, load test, reading of earth pressure cell and etc. The reinforcement of the vibro-replacement stone piles could reach the expected reinforcement effect for the soft earth foundation. After the application of the piles, the carrying fore of the composite foundation is higher than the design requirements and the liquefaction resistance has experienced significant improvement. Moreover, this kind of composite soil foundation could effectively reduce the total settlement of the foundation, accelerate the consolidation of the foundation and improve the hydraulic conductivity of the foundation.

Abstract: The foundation on slope problem is a special case of the very large bearing capacity problem. Researchers have studied the bearing capacity of slopes as such problems arise quite frequently in practice. The aim of this paper is to study the effect that changing the position of an infinitely long strip foundation, from the edge of the slope to a certain distance away, has on the bearing capacity of a slope. The influence of various nondimensional parameters, such as strength ratio, slope height ratio and so on, on the bearing capacity of slope foundation is also analyzed by the finite element method. Conclusions are as follows: as the foundation is moved away from the slope by increasing D/B, there is a change over point from a slope failure mechanism to a flat ground failure mechanism. As the strength ratio increases for a set D/B, there is a considerable change in the shape of the failure surface initially, followed by only minor changes from strength ratio 10 onwards and so on.

Abstract: Three-dimensional non-linearity finite element model of shield tunnel was established on basis of the Z1 line of Tianjin subway. And then it was applied to simulate construction process of shield tunnel. Surface settlement of the tunnel during the construction was obtained. The settlement data of transverse and longitudinal direction from numerical simulation were fitted through a polynomial expression. Then a contrastive analysis of curves from numerical simulation and matching formulae were made. The result shows that it is feasible to utilize the empirical formulas like Pecks to predict surface settlement in Tianjin caused by shield construction.

Abstract: Based on MTS-810 type vibration testing machine, morphological characteristics of hysteretic curves of frozen clay are quantitatively studied, and dynamic mechanical response are analyzed consisting of stiffness, viscosity, degree of microscopic damage, residual strain and energy dissipation. The studies have shown that the higher vibration frequencies are, the greater the stiffness is, while the smaller viscosity, the degree of microscopic damage, residual strain and energy dissipation are. Stiffness, viscosity, degree of microscopic damage, residual strain and energy dissipation are less affected by confining pressure. With increasing dynamic stress amplitude, stiffness decreases gradually, while viscosity, degree of microscopic damage, residual strain and energy dissipation increase gradually.

Abstract: Drain hole is a important structural measure in retaining wall constructions The necessity of retaining wall drainage holes and its side effects were discussed in the paper. A solution is proposed to deal with water seepage pollution with the use of leading channel, which is demonstrated in some practical project. The project shows that dark tank to guide water is characteristiced with low cost, short construction period and reliable effect, which is worthy of reference in other similar projects.

Abstract: The combined effect of the embankment fill, piles and caps, and foundation soils on the load transfer characteristics of sparse capped-piled embankment is very significant. Using the modified cylindrical shear stress transfer model based on Marston soil pressure theory, a new calculation method for pile-soil stress ratio of sparse rigid pile composite foundation incorporating the arching effect in lime-soil and soil-pile interaction was presented. The presented method is verified by comparison between analytical solutions and the observed results from a practical project. In addition, a parametric study was also conducted to evaluate the influence of the embankment height, the cohesion of fill and pile-soil stiffness ratio on the pile-soil stress ratio.

Abstract: The immersed tube tunnels in Yangtze river delta region are affected severely by back-silting. Back-silting is difficult to control during construction and the consequences are hard to evaluate as well. In this study, sedimentation experiment was conducted incorporating back-silting soil solutions with different concentration ratios, and compression tests on the initial sedimentation layers was also conducted based on back-silting soil specimens taken from the back-silting soil sedimentary layers located in the surrounding area of Shenjiamen harbor undersea immersed tube tunnel in Zhoushan City. The undersea back-silting was assessed from the aspect of sedimentation speed and the strength of initial sedimentary layers. Results from the study are essential for further study of back-silting load and the effect of back-silting on settlement.

Abstract: The O-cell method which was applied on the pile testing was introduced, including the basic principle, test device and test technique. The advantages of O-cell method compared to traditional pile testing method were also illustrated. Based on the project of offshore structure in Mozambique, the O-cell test was performed on the long drilled rock socked pile. The results were converted to the traditional load-settlement curve to analyze the bearing behavior and load transfer characteristics. The regularity of axial force and shaft friction of rock socked pile were also revealed.