Modeling strategy for jointed rock masses reinforced by rock bolts in tunneling practice   总被引：2，自引：1，他引：1  

Shunsuke Sakurai 《Acta Geotechnica》2010,5(2):121-126

This paper deals with the modeling of jointed rock masses reinforced by rock bolts. It is well known that rock bolts are extremely effective in reinforcing jointed rocks. However, if a continuum approach is adopted for modeling jointed rock masses, it is often misleading to evaluate the effectiveness of the rock bolts by numerical analyses such as the finite element method. This may be due to the fact that since no more joints exist in the continuum, the effectiveness of the rock bolts in constraining the relative displacements along the joints cannot be evaluated properly. In order to investigate the reinforcement effect of rock bolts, physical model tests were performed in the laboratory. The test results revealed that jointed rock masses should be modeled as an equivalent continuum after the installation of rock bolts and that the mechanical parameters of the equivalent continuum should be evaluated by considering the reinforcement effect of the rock bolts. Therefore, the values of the mechanical parameters differ from place to place in accordance with the relation between joint orientation and rock bolt direction, even though joint systems are homogeneous. In conclusion, in the continuum approach for modeling jointed rock masses, it should be emphasized that rock bolts and jointed rock masses should not be modeled separately but should be modeled simultaneously by considering the reinforcement effect of the rock bolts in constraining joint movement. The modeling of shotcrete reinforced by steel ribs is also discussed in comparison to the modeling by rock bolts.  相似文献   

The three-dimensional shear wave structure in the mantle by overtone waveform inversion - I. Radial seismogram inversion     

Toshiro Tanimoto 《Geophysical Journal International》1987,89(2):713-740

Summary. The three-dimensional (3-D) shear wave structure of the mantle, down to the depth of about 900 km, is obtained by inverting waveforms of radial component seismograms. Radial component seismograms contain large amplitude overtone signals which circle the Earth as wave packets and are sometimes called X1, X2, X3, … We use data which contain R1, X1 and X2 and filtered between 2 and 10mHz. It is shown that, unless each seismogram is weighted, all seismograms are not fitted uniformly. Only data from large earthquakes are fitted and the final velocity anomalies are biased by the small number of large earthquake data. Resolution is good at shallow depths, becomes worse in the intermediate depth range between about 400 and 500 km and then becomes better at greater depth ranges (600–900km). Even though we use only spheroidal mode data, velocity anomalies in the shallow structure show excellent correlation with the age of the surface rocks of the Earth. In the deeper regions, between about 600 and 900km, South America shows a fast velocity anomaly which may indicate the slab penetration beyond 700 km there. Another region which shows a fast velocity anomaly is the Mariana trench, but other subduction regions do not show such features.  相似文献   

The 3-D shear wave structure in the mantle by overtone waveform inversion-II. Inversion of X-waves, R-waves and G-waves   总被引：1，自引：1，他引：0  

Toshiro Tanimoto 《Geophysical Journal International》1988,93(2):321-334

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Reply     

Toshiro Tanimoto 《Geophysical Journal International》2004,159(1):369-369

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Back analysis procedures for the interpretation of field measurements in geomechanics     

Giancarlo Gioda  Shunsuke Sakurai 《国际地质力学数值与分析法杂志》1987,11(6):555-583

A survey is presented of some recent developments of the numerical techniques for back analysis in the field of geomechanics, with particular reference to tunnelling problems. In the spirit of Terzaghi's observational design method, these techniques are seen as practical tools for interpreting the available field measurements, in order to reduce the uncertainties that in many instances affect the parameters governing the solution of complex geomechanics problems. Both deterministic and probabilistic viewpoints are considered and some significant applications to practical problems are illustrated.  相似文献   

Tectonic signatures in coseismic gravitational energy change   总被引：3，自引：0，他引：3  

Toshiro Tanimoto  Taro Okamoto  Fabia Terra 《Geophysical Journal International》2002,149(2):490-498

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A comparative approach to modelling multiple urban land use changes using tree-based methods and cellular automata: the case of Greater Tokyo Area     

Guodong Du  Liang Yuan  Shunsuke Managi 《International journal of geographical information science》2018,32(4):757-782

Urban multiple land use change (LUC) modelling enables the realistic simulation of LUC processes in complex urban systems; however, such modelling suffers from technical challenges posed by complicated transition rules and high spatial heterogeneity when predicting the LUC of a highly developed area. Tree-based methods are powerful tools for addressing this task, but their predictive capabilities need further examination. This study integrates tree-based methods and cellular automata to simulate multiple LUC processes in the Greater Tokyo Area. We examine the predictive capability of 4 tree-based models – bagged trees, random forests, extremely randomised trees (ERT) and bagged gradient boosting decision trees (bagged GBDT) – on transition probability prediction for 18 land use transitions derived from 8 land use types. We compare the predictive power of a tree-based model with multi-layer perceptron (MLP) and among themselves. The results show that tree-based models generally perform better than MLP, and ERT significantly outperforms the three other tree-based models. The outstanding predictive performance of ERT demonstrates the advantages of introducing bagging ensemble and a high degree of randomisation into transition probability modelling. In addition, through variable importance evaluation, we found the strongest explanatory powers of neighbourhood characteristics for all land use transitions; however, the size of the impacts depends on the neighbourhood land use type and the neighbourhood size. Furthermore, socio-economic and policy factors play important roles in transitions ending with high-rise buildings and transitions related to industrial areas.  相似文献   

State of stress within a bending spherical shell and its implications for subducting lithosphere     

Toshiro Tanimoto 《Geophysical Journal International》1998,134(1):199-206

The state of stress within a bending spherical shell has some special features that are caused by sphericity. While most lithospheres are more like spherical shells than flat plates, our ideas of the state of stress have been dominated by flat-plate models. As a consequence, we might be missing some important aspects of the state of stress within subducting lithospheres. In order to examine this problem, we analyse spherical-shell bending problems from basic equations. We present two approaches to solve spherical-shell bending problems: one by the variational approach, which is suitable for global-scale problems, and the other by the asymptotic equation, which is valid to first order in h/R , where h is the thickness of the lithosphere and R is its curvature radius (i.e. under the assumption of small curvature). The form of the equation for displacement shows that wavelengths of deformation are determined by the spherical (elastic) effect and the gravitational buoyancy effect, for which only the latter effect is included in the usual flat-plate formulations. In the case of the Earth, the buoyancy force is dominant and, consequently, spherical effects are suppressed to a large extent; this explains why flat-plate models have been successful for Earth's lithospheric problems. On the other hand, the state of stress shows interesting spherical effects: while bending (fibre) stress along the subduction zone is always important, bending stress along the trench-strike direction can also be important, in particular when the subduction zone arc is small. Numerical results also indicate that compressive normal stress along the trench-strike direction is important when a subduction zone arc is large. These two stresses, the bending stress and the compressive normal stress, both along the trench-strike direction, may have important implications for intraplate earthquakes at subduction zones.  相似文献   

Temporal variation of resuspended matter for one tidal cycle in the Hiuchi-Nada area     

Kichiichiro Kawana  Terumi Tanimoto 《Journal of Oceanography》1981,37(4):173-178

The observed relation between the vertical distribution of suspended matter and the size distribution of bottom sediment in the Hiuchi-Nada area indicates that a turbid bottom water layer exists above the bottom when the bottom sediment is of silt size. The turbid bottom water is thought to be produced by resuspension of bottom sediment. Measurements of the temporal variation of resuspended matter and water movement near the bottom was carried out for one full tidal cycle at an anchored station. The concentration of resuspended matter reached a maximum at the time of strongest ebb and flood flow.  相似文献   

Vertical distributions of nitrogen,phosphorus and iron in Beppu Bay     

Yukiho Yamaoka  Terumi Tanimoto  Takayuki Shiozawa 《Journal of Oceanography》1983,39(6):301-304

Beppu Bay is a shallow basin located at the western end of the Seto Inland Sea with a sill depth ofca. 40 m. The bottom water (belowca. 65 m in summer andca. 70 m in winter) was anoxic and contained high concentrations of hydrogen sulfide, phosphate and ammonium. Maximum concentrations of nitrate and nitrite appeared near the top of the thermocline, suggesting the occurrence of bacterial nitrification in this layer and of bacterial denitrification in the anoxic bottom water. Concentrations of particulate phosphorus and particulate iron were highest near the bottom of the thermocline. The distribution of phosphorus in this bay is probably controlled by a dissolution-diffusion-precipitation cycle of iron or its hydrous oxides.  相似文献