Deformation analysis of soft ground reinforced by columnar inclusions   总被引：20，自引：0，他引：20  

M. Alamgir  N. Miura  H.B. Poorooshasb  M.R. Madhav 《Computers and Geotechnics》1996,18(4):267-290

A simple theoretical approach to predict the deformation behaviour of soft ground reinforced by columnar inclusions such as stone columns./granular piles, sand compaction piles, lime or cement columns, etc., is presented in this paper. The analysis is performed based on the deformation properties of the column material and the surrounding soil. The interaction shear stresses between the column and the surrounding soil are considered to account for the stress transfer between the column and the soil. The solution is obtained by imposing compatibility between the displacements of the column and the soil for each element of the column-soil system. Numerical evaluations are made for a range of parameters to illustrate the influence of various parameters on the predictions. The proposed method is verified with finite element analysis and a reasonable agreement is obtained between the predictions.  相似文献   

Molecular dynamics simulations of the phase transition between low-temperature and high-temperature clinoenstatites     

N. Shimobayashi  A. Miyake  M. Kitamura  E. Miura 《Physics and Chemistry of Minerals》2001,28(9):591-599

 Phase transition between low-temperature clinoenstatite (LT-CEn) and high-temperature clinoenstatite (HT-CEn) was studied by using molecular dynamics (MD) simulations, based on empirical potential parameters. Starting from LT-CEn, the MD calculations were carried out at atmospheric pressure and at elevated pressures (1–6 GPa). At elevated temperatures the transformation from the starting LT-CEn to HT-CEn occurred at any pressure. It was confirmed that the HT-CEn has the same space group C2/c as diopside but the M2 site is six-coordinated, unlike diopside. A significant difference in the MD-simulated cell volumes between LT-CEn and HT-CEn was also observed, showing a first-order transition. In addition, there were some temperature ranges where LT-CEN and HT-CEn would be coexistent and very small thermal hystereses between increasing and decreasing temperatures during the transition. These behaviors are consistent with the characteristic of a thermoelastic-martensitic transformation. The phase boundary between LT-CEn and HT-CEn was determined for the first time. Its positive dT/dP slope strongly shows that the high-pressure clinoenstatite is a significantly distinct phase from HT-CEn although the both phases have the same space group, C2/c. Received: 8 November 2000 / Accepted: 28 April 2001  相似文献   

The effects of liquefaction-induced lateral spreading on pile foundations     

F. Miura 《Soil Dynamics and Earthquake Engineering》1991,10(5)

Observations of pile foundation performance during previous earthquakes have shown that pile failure has been caused by lateral ground movements resulting from soil liquefaction. The recognition that lateral ground movements may play a critical role in pile performance during an earthquake has important implications for design and risk assessment, and requires that analytical models be devised to evaluate these potential problems.In this paper, parametric studies were conducted to estimate the maximum bending moments induced in piles subjected to lateral ground displacement. The results are summarized in charts using dimensionless parameters.The analyses reveal that the existence of a nonliquefiable layer at the ground surface can affect significantly the maximum bending moment of the pile. When a relatively thick nonliquefiable layer exists above a liquefiable layer, neither the material nonlinearity of the soil nor loss of soil stiffness within the liquefiable layer significantly affect the maximum bending moment. When the thickness of the liquefiable soils is greater than about three times that of an overlying intact layer, soil stiffness in the liquefiable layer must be chosen carefully when evaluating the maximum bending moment.  相似文献   

Equivalent linear method considering frequency dependent characteristics of stiffness and damping   总被引：4，自引：0，他引：4  

Nozomu Yoshida  Satoshi Kobayashi  Iwao Suetomi  Kinya Miura 《Soil Dynamics and Earthquake Engineering》2002,22(3)

Equivalent linear dynamic response analysis of ground is based on complex moduli and Fourier series expansion; therefore, it is not an equivalent method but an approximate method. Two deficiencies in the conventional equivalent linear method represented by SHAKE are described first. The maximum shear strength is overestimated, resulting in overestimation of the peak acceleration under a strong ground motion, and the amplification is underestimated at high frequency. The latter sometimes results in underestimation of the peak acceleration under weak ground shaking, and gives an incident wave with unrealistic large accelerations or a divergence of analysis in deconvolution analysis under strong ground motion. Both deficiencies are shown to come from the same cause, i.e. computing the effective strain as a constant fraction of the maximum strain. Since this is a key concept of the equivalent linear analysis, one cannot overcome both deficiencies at the same time in the conventional method. An apparent frequency dependence in stiffness and damping is shown to appear in the dynamic response, although soil itself does not show frequency dependent characteristics. Following this observation, the effective strain is expressed in terms of frequency from the similarity concept of the strain–frequency relationship between time domain and frequency domain. This enables the reduction of both deficiencies at the same time, resulting in a marked improvement in the equivalent linear analysis. The accuracy of the proposed method is examined by the simulations of three vertical array records during large earthquakes. The proposed method always gives much better prediction than conventional equivalent linear methods for both convolution and deconvolution analyses, and it is confirmed to be applicable at more than 1% shear strain.  相似文献   

Structural characteristics off Miyagi forearc region, the Japan Trench seismogenic zone, deduced from a wide-angle reflection and refraction study   总被引：4，自引：0，他引：4  

Seiichi Miura  Narumi Takahashi  Ayako Nakanishi  Tetsuro Tsuru  Shuichi Kodaira  Yoshiyuki Kaneda 《Tectonophysics》2005,407(3-4):165-188

The Japan Trench subduction zone, located east of NE Japan, has regional variation in seismicity. Many large earthquakes occurred in the northern part of Japan Trench, but few in the southern part. Off Miyagi region is in the middle of the Japan Trench, where the large earthquakes (M > 7) with thrust mechanisms have occurred at an interval of about 40 years in two parts: inner trench slope and near land. A seismic experiment using 36 ocean bottom seismographs (OBS) and a 12,000 cu. in. airgun array was conducted to determine a detailed, 2D velocity structure in the forearc region off Miyagi. The depth to the Moho is 21 km, at 115 km from the trench axis, and becomes progressively deeper landward. The P-wave velocity of the mantle wedge is 7.9–8.1 km/s, which is typical velocity for uppermost mantle without large serpentinization. The dip angle of oceanic crust is increased from 5–6° near the trench axis to 23° 150 km landward from the trench axis. The P-wave velocity of the oceanic uppermost mantle is as small as 7.7 km/s. This low-velocity oceanic mantle seems to be caused by not a lateral anisotropy but some subduction process. By comparison with the seismicity off Miyagi, the subduction zone can be divided into four parts: 1) Seaward of the trench axis, the seismicity is low and normal fault-type earthquakes occur associated with the destruction of oceanic lithosphere. 2) Beneath the deformed zone landward of the trench axis, the plate boundary is characterized as a stable sliding fault plain. In case of earthquakes, this zone may be tsunamigenic. 3) Below forearc crust where P-wave velocity is almost 6 km/s and larger: this zone is the seismogenic zone below inner trench slope, which is a plate boundary between the forearc and oceanic crusts. 4) Below mantle wedge: the rupture zones of thrust large earthquakes near land (e.g. 1978 off Miyagi earthquake) are located beneath the mantle wedge. The depth of the rupture zones is 30–50 km below sea level. From the comparison, the rupture zones of large earthquakes off Miyagi are limited in two parts: plate boundary between the forearc and oceanic crusts and below mantle wedge. This limitation is a rare case for subduction zone. Although the seismogenic process beneath the mantle wedge is not fully clarified, our observation suggests the two possibilities: earthquake generation at the plate boundary overridden by the mantle wedge without serpentinization or that in the subducting slab.  相似文献   

Temporal change of interplate coupling in northeastern Japan during 1995–2002 estimated from continuous GPS observations     

Takuya Nishimura  Tomowo Hirasawa  Shin'ichi Miyazaki  Takeshi Sagiya  Takashi Tada  Satoshi Miura  Kazuo Tanaka 《Geophysical Journal International》2004,157(2):901-916

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Water requirements for cultivatingSalicornia bigeloviiTorr. with seawater on sand in a coastal desert environment     

Edward Glenn  Seiichi Miyamoto  David Moore  J.Jed Brown  T.Lewis Thompson  Paul Brown 《Journal of Arid Environments》1997,36(4):711-730

The forage and oilseed halophyte,Salicornia bigeloviiTorr., was grown in gravity-drained lysimeters set in open plots of the same crop over two seasons in a coastal desert environment in Sonora, Mexico. The lysimeters were irrigated daily with seawater (40 g l⁻¹salts) at rates ranging from 46–225% of potential evaporation. Biomass and seed yields increased with increasing irrigation depth over the range of treatments. Biomass yields ranged from 13·6–23·1 t DM ha⁻¹, equivalent to conventional forage crops, on seasonal water application depths of 2·3–3·8 m, but were markedly lower at lower irrigation depths. Increasing the irrigation depth lowered the soil solution salinity, resulting in greater growth and water use, and hence leaching fractions that were nearly even over irrigation treatments, averaging 0·5. Evapo-transpiration rose in direct proportion to the irrigation depth. Potential evaporation was estimated by site pan evaporation and by the Blaney-Criddle and Penman models using climatological data; the methods agreed within 15%. The ratio of evapo-transpiration to potential evaporation increased over the growing season and approached 1·5 by pan on the highest irrigation treatment due to the combined effects of high transpiration and high evaporation from the permanently moist soil surface. The best field predictor of biomass yield was the salinity of the soil moisture in the top 15 cm of soil profile, which constitutes the root zone for this crop. Root zone salinity must be kept at 70–75 g l⁻¹for high yields. Although irrigation and drainage requirements were high compared to conventional crops, seawater irrigation appears to be feasible in medium sand and could augment crop production along coastal deserts. The possibility of using this crop for animal production is discussed.  相似文献   

Counter-clockwise rotation of the eastern part of the Mongolia block: Early Cretaceous palaeomagnetic results from Bikin, Far Eastern Russia     

Yo-ichiro Otofuji  Daisuke Miura  Koichi Takaba  Kazuhiro Takemoto  Kazutoshi Narumoto  Haider Zaman  Hiroo Inokuchi  Ruslan G. Kulinich  Petr S. Zimin  Vladimir G. Sakhno 《Geophysical Journal International》2006,164(1):15-24

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日本绒螯蟹线粒体DNA序列研究I.12S rRNA   总被引：5，自引：0，他引：5  

高天翔  张秀梅  吉崎悟朗  渡边精一 《中国海洋大学学报(自然科学版)》2000,30(1):43-47

参考果蝇与蚤状  相似文献   

日本绒螯蟹线粒体DNA序列研究Ⅱ.16S rRNA   总被引：2，自引：2，他引：0  

高天翔  任一平  张秀梅  渡边精一  杨永恒 《中国海洋大学学报(自然科学版)》2000,30(3):482-486

参考果蝇、卤虫与锯缘青蟹的线粒体 DNA16 S r RNA基因序列进行了日本绒螯蟹相同基因片段的引物设计、PCR扩增及序列测定 ,得到 56 7bp的碱基序列 ,其 A、T、G、C含量分别为194 bp(34.2 2 % )、2 16 bp(38.10 % )、98bp(17.2 8% )、59bp(10 .4 1% ) ,与果蝇、卤虫及锯缘青蟹类的 16 S r RNA基因片段序列含量相似。  相似文献