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221.
Engineering geological studies and tunnel support design at Sulakyurt dam site, Turkey 总被引:2,自引:0,他引:2
H. Basarir 《Engineering Geology》2006,86(4):225-237
This paper presents the results of engineering geological investigations and tunnel support design studies, carried out at the Sulakyurt dam site, northeast of Ankara, Turkey. The Sulakyurt dam will be used for flow control and water storage for irrigation projects. Studies were carried out both in the field and the laboratory. Field studies include engineering geological mapping, intensive discontinuity surveying, core drilling and sampling for laboratory testing. The diversion tunnel will be driven in rock mass, consisting of granite and diorite. Empirical, analytical and numerical methods were combined for safe tunnel design. Rock mass rating (RMR), Rock mass quality (Q) and Geological strength index (GSI) systems were used for empirical rock mass quality determination, site characterization and support design. The convergence–confinement method was used as analytical method and software called Phase2, a 2D finite element program, was utilized as numerical method. According to the results acquired from the empirical, analytical and numerical methods, tunnel stability problems were expected in both granite and diorite rock masses. The support system, suggested by empirical methods, was applied and the performance of suggested support system was evaluated by means of numerical modelling. It was concluded that the suggested support systems were adequate, since after applying the suggested support system to granite and diorite, tunnel deformation and the yielded elements around the tunnel decreased significantly. Thus, it is suggested that for more reliable support design empirical, numerical and analytical methods should be combined. 相似文献
222.
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224.
A sequential waveform method is developed to simulate the seismic response of basin-edge structure excited by a plane incident P-wave. The full procedure involves: (a) a previous parameterization of the investigated model using the seismic wave velocities and depths of the sedimentary stratifications; (b) an input motion determined from the records at stations installed on hard rock; (c) forward computation of the P-SV elastic wave field by means of a two-dimensional finite difference (FD) method; (d) the optimization of the model vector using simulated annealing technique and comparing the simulated seismic response of the tested structure with the observed wave field; (e) the correction of the initial model by trial-and-error by testing the differences between synthetics and observed data, and (f) the final solution obtained by iteration using the conjugate gradient algorithm. The search of an optimal basin-edge model has been parallel processed by varying the shapes and velocities of strata on the basis of the fitting of relative timing, amplitude and phase between the output and the observed data. The input motion and sensitivity have been checked and the validity of the method has been demonstrated by numeric analysis. Using the teleseismic records generated by 7 earthquakes recorded at 26 broadband seismic stations, we have studied the seismic velocity structure of the southern edge of the Jiyang depression located in the Bohai Bay basin, northern China. Two cross sections show an agreement between the velocity results and the geological sections available in the region. In addition, we obtain evidence of three hidden faults under the sections and features that suggest major extensions at the Paleogene. 相似文献
225.
A numerical procedure is described for the analysis of the vertical deformation and the stress distribution of the strip footings
on layered soil media. Three layers of soil with different stiffness are considered with the middle soil layer the thinnest
and most stiff layer. The soil media is discretized and using the theory of elasticity, the governing differential equations
are obtained in terms of vertical and horizontal displacements. These equations along with appropriate boundary and continuity
conditions are solved by using the finite difference method. The vertical and horizontal displacements, strains and stresses
are found at various nodes in the soil media. Parametric studies are carried out to study the effect of the placement depth
of the middle soil layer, the relative ratios of the moduli of deformation of the soil layers on the vertical displacement
of the footing and the vertical stress distribution. These studies reveal that the middle thin but very stiff layer acts like
a plate and redistributes the stresses on the lower soft soil layer uniformly. The displacement on the top and bottom of the
middle soil layer is almost the same showing that the compression of the middle layer is negligible as it is very stiff. 相似文献
226.
Performance of Mortar and Chemical Grout Injection into Surrounding Soil When Slurry Pipe-jacking Method is Used 总被引:1,自引:0,他引:1
Hideki Shimada Takashi Sasaoka Saeid Khazaei Yasuhiro Yoshida Kikuo Matsui 《Geotechnical and Geological Engineering》2006,24(1):57-77
Small-diameter shallow tunnels are often being built by using the slurry pipe-jacking method. This system involves the pushing
or thrusting of a drivage machine and concrete pipes into the ground. Chemical grout injection into the surrounding soil around
the tunnel is carried out after the drivage and pushing processes are finished. The purpose of the chemical grout injection
is to maintain permanent stability of the surrounding soil. However, the behavior of the chemical grouting material in the
surrounding soil around the tunnel and the amount of optimum injection is not clearly understood. From these points of view,
this paper discusses the performance of the chemical grouting material, when it is injected into the surrounding soil around
the tunnel, by means of 2-D Eulerian–Lagrangian seepage analysis. Moreover, the effectiveness of the chemical grout injection
was evaluated by using the non-linear finite element method. This investigation show when the range of the grouted zone is
designed; it is necessary that the relationship between Young’s modulus of the soil/grouted zone and the confining stress
be taken into consideration in order to establish effective, economical and safe chemical grout injection system. Understanding
the performance of the seepage/dispersion behavior of the chemical grout and the characteristics of soil/ grouted zone is
also important. 相似文献
227.
River bank erosion control by soil nailing 总被引:2,自引:0,他引:2
A study has been done for analysing soil nailed cuts with circular type wedge failure by friction circle method. Various parameters
such as nail length, nail diameter, nail inclination, wall inclination and angle of internal friction of soil have been considered
to determine the factor of safety of nailed open cuts. The study shows that for cohesionless soil nailed cut, factor of safety
increase with increase of parameters like angle of internal friction of soil, length of nail (L) versus height of cut (H) ratio, cohesion of soil and nail inclination (upto 15°) with horizontal. The study revealed that nails grouted with cement
perform better than driven nails. A case study further confirms the analytical findings.
Received 7 October 相似文献
228.
采用密闭室红外气体分析仪法(IRGA法)观测了中亚热带红壤侵蚀裸地植被恢复后不同季节土壤呼吸速率的日动态变化,并比较了IRGA法与碱吸收法(AA法)测定的土壤呼吸速率.结果表明:侵蚀裸地植被恢复后土壤呼吸速率日动态呈单峰曲线,与土壤温度的昼夜变化基本一致,最高值一般出现在午后13∶00~17∶00,最低值出现在凌晨3∶00~7∶00;植被恢复显著提高了土壤日呼吸速率,但明显降低了土壤呼吸速率日变化幅度;马尾松林对土壤呼吸速率日变化幅度降低程度高于板栗园和百喜草地,且对夏季的降低程度影响最大.而IRGA法和AA法测定的土壤呼吸速率具有显著的幂函数关系,AA法测定的土壤呼吸速率为IRGA法的27.5%~218%,平均为76.2%.当土壤呼吸速率较低时,AA法比IRGA法高估了土壤呼吸速率;反之,AA法则低估了土壤呼吸速率. 相似文献
229.
Traction image method for irregular free surface boundaries in finite difference seismic wave simulation 总被引:16,自引:1,他引:16
In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem. 相似文献
230.