Applied Mechanics and Materials Vols. 90-93

Abstract: Based on an engineering example of a certain shield tunnel passing through an intercity high-speed railway station which has been reinforced by pile-slab structure, this paper adopts finite element numerical simulation to study the influence of shield tunneling construction on the pile-slab reinforced structure and railway subgrade. The research result shows that the horizontal displacement and additional bending moment on both sides of bored piles are increasing in the process of shield tunneling, while those of the middle bored pile firstly increase and then decrease. The vertical displacement and axial force variation of the middle bored pile are more obvious than that on both sides of the bored piles. The settlement and additional bending moment of the reinforced concrete slab are relatively large in the center and midspan of both sides, the position of maximum settlement and negative bending moment is near the concrete slab just above the right tunnel, while the maximum positive bending moment is located in the very middle of the concrete slab. The pile-slab reinforced structure can effectively control the settlement and differential settlement of the intercity railway subgrade caused by shield tunneling, thus the intercity railway can keep normal operation.

Abstract: The surface settlement and tunnel lining has a great relationship.To better understand the influence of surface deformation caused by tunnel lining and lining’s stress state,base on Finite Element Method,using ABAQUS Finite Element Analysis Software, analyzed the change of surface displacement and the lining of stress and deformation,respectively,with and without lining.Through the comparison of two cases, the surface settlement and horizontal displacement can be effectivly reduced.The range of influence caused by excavation is greatly narrowed.Because the role of soil,the compressive stress is beared by lining,and the maximum stress is located at both sides of arch waist. These will be referenced for future design and construction.

Abstract: Piles have been used in geotechnical engineering to stabilize slope for many years and the methodology has been accompanied by a significant bibliography. In the past, methods of analysis of pile-reinforced slopes have often used limit equilibrium methods, where rock–pile interaction was not properly considered. Recently, with rapid development of computer techniques, numerical methods using either finite element or finite difference methods have been widely applied in slope engineering, and have been shown to offer many advantages over limit equilibrium method, such as the ability to develop the critical failure surface automatically with fewer assumptions. However, seldom studies have been done on the stratified rock slope reinforced by piles, so in the present paper, the numerical simulation software FLAC3D is adopted to model the stratified rock slope, then the reinforced effect like deformation and stress of slope are studied, to give guidance for the real practice.

Abstract: Longitudinal wave velocity and shear wave velocity of two kinds of the soil-rock mixture samples with different stone content and water content are tested. Then the poisson ratio of the samples in Low Strain can be calculated with the method of wave velocity testing. Analyzing the relationship between poisson ratio, water content and stone content, the dualistic nonlinear models of poisson ratio, water content and stone content are established. The result of verifying is shown that the absolute error of poisson ratio is less than 0.01 and the relative error is less than 2%. The models not only can show the relationship between poisson ratio, water content and stone content but can provide the reference when changing the Rayleigh wave velocity to shear wave velocity each other.

Abstract: To combine the characters of metro pits and time-space effect, an approximate prediction method is studied. Sub-step excavation width, depth, unsupported exposure time and space effect are the main reasons for the displacement of excavation. To calculate the comparative displacement ratios of different parameters variational conditions and standard excavation condition, the displacement effective modulus of every parameter are obtained, and the differences of every layer excavation are also considered. The displacement of excavation can be predicted when the excavation parameters changed based on this method, and the displacement can be controlled by modulating the excavation parameters.

Abstract: A number of nodes at different strata positions of tunnel roof were selected as research objects, the law between the roof deformation and the speed or acceleration time-history of horizontal and vertical direction were simulated on conditions of inputting earthquake wave at particular lacation of deep tunnel floor. With the gradually increasing distance from tunnel top surface, the “high -low-high” law of peak values were performed in speed time-history and acceleration speed time-history curves. One peak value was overally performed on vertical speed time-history curves, but multiple peak fluctuation was indicated in vertical acceleration time-history, horizontal speed and horizontal accelaration time-history curves.

Abstract: Based on the practical engineering ,by using the 3D-FEM of elastic-plasticity, a reasonable model for simulation of tunnel excavation and shotcrete lining and rock bolts builds up, surrounding rock using Mohr-Coulomb constitutive model of ABAQUS, lining using Concrete Damaged Plasticity constitutive model, and bolt using elastic-plasticity constitutive model. By using strength reduction finite element method, analysis for safety coefficient of stability of surrounding rock with primary shotcrete lining and rock bolts under the four limit state criteria. It is concluded that the appearance of divergence of the computation may precede by displacement of characteristic points, The safety coefficient of the running-through of the plastic zone of the surrounding rock and the running-through of the plastic zone of the shotcrete and a great amount of rock bolts yielding are less than the divergence of the computation and displacement of characteristic points.

Abstract: In order to get the seismic active earth pressure with the mode of translation, adopting some related assumptions of the M-O theory, this paper establishes the first-order differential equation of the Seismic active earth pressure by horizontal slices analysis method and gets the solution of the seismic active earth pressure by boundary conditions. This formula can solve the distribution of the seismic active earth pressure is nonlinear along the wall, the point of application of the dynamic active thrust which is the advantage of this formula and announces the decreasing process of the filling’s rupture angle with the increase of the horizontal peak ground acceleration (PGA) , as well. The rationality and validity of the formula is confirmed by the comparison between the results of the shaking table tests and the formula, respectively. If the retaining wall takes place the mode of translation, the point of application of the seismic active thrust ranges between 0.4 and 0.5 times wall’s height at the horizontal seismic peak ground acceleration (PGA)<0.4g.At the same time, the computational accuracy of the dynamic active thrust, their points of application and the angle of rupture increases with the increase of the horizontal peak ground acceleration at the horizontal PGA<1.0g, as the astigmatic of the retaining wall in highly seismic intensity region supplying the valuable reference.

Abstract: Based on the comprehensive analysis on the primary components of ground movement associated with earth pressure balance (EPB) shield tunneling, a three-dimensional nonlinear finite element model for simulating EPB shield tunneling is proposed. The proposed modeling techniques are applied to simulate a tunneling project. The distributions of soil displacement on the ground surface associated with the advance-ment process of shield tunnel are analyzed. According to the comparisons of numerical results with field measurements, the proposed numerical procedure is found to be an effective approach for predicting the deformation dun to shield tunneling. The further analysis shows that the computed results of the small-strain constitutive model are more reasonable, and the small-strain mechanical behaviors of soils should be taken into account

Abstract: With the increasement of mining depth, the strata behavior of the roadway is obvious. As the stress of surrounding rock increases, the bottom of the soft rock roadway becomes deformed easily compressed by its top rock and two sides rock, which leads to the occurrence of the pucking and roadway destruction. Aiming the air inlet roadway destruction phenomenon of -450th level powder magazine in Hebi Zhongtai Mining Co.Ltd, the geological condition and the mechanism of the roadway failure are analysed comprehensively, and the bolt-grout supporting method is also proposed in this paper. At last, the deformation and heaving floor are controlled effectively which is proved by the field monitoring results.