A model of the formation and development of ocean shear wave

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雪峰山中段含金剪切带特征及其动力学机制浅析

雪峰山中段为区域性剪切变形带,区内分布了众多与剪切带有关的金矿床（点）。作者分析了区域地质背景和剪切带特征,认为剪切带的规模、产状及形态,受控于发生剪切带变形的相对构造软弱层;剪切作用机制取决于水平挤压与剪切带的交切关系。     

不同前期固结压力下粉砂类滑带土抗剪强度环剪试验研究

滑带土残余强度的确定对于复活型滑坡稳定性及滑坡运动分析极其重要。黏性土滑带土环剪试验研究成果较多,但对于粉砂类滑带土这种特性不规则的土体则研究较少,粉砂类土常表现出复杂的剪切特性。本文利用环形剪切仪对粉砂类滑带土在不同前期固结压力下的抗剪强度特性进行试验研究,研究不同超固结比对粉砂类滑带土抗剪强度特性的影响,尤其是前期固结压力对滑带土残余强度的影响。试验结果表明：通过对滑带土分别施加600、500、400kPa的前期固结压力,并与正常固结的样品对比研究,发现在相同正应力（50、100、200kPa）下剪切,前期固结压力对粉砂类滑带土峰值强度影响明显,峰值强度随着超固结比呈现线性增加;不同应力历史对粉砂类滑带土的残余强度影响并不显著,其残余强度与超固结比无关。     

Shear strength characterization of municipal solid waste at the Suzhou landfill, China

The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill.     

一次区域性暴雪天气过程的诊断分析

利用Micaps常规天气资料和NCEP 1°×1° 6h再分析资料．采用天气学诊断方法．对2006年2月27日十堰市出现的一次区域性暴雪天气过程的环流特征和物理量场特征进行了分析。结果表明,此次区域性暴雪天气过程是在比较有利的天气背景条件下发生的,高空东移小槽、中低层切变线和地面冷锋是其主要的影响系统;中低层较强的暖湿气流（暖平流）沿低层冷空气垫爬升是产生强降雪的动力条件;强烈的水汽辐合为暴雪的产生提供了充足的水汽,暴雪区位于近似西南-东北向水汽通量轴线的左侧。     

Directional dependence of P- and S-wave propagation and polarization in foliated rocks from the Kola superdeep well: Evidence from laboratory measurements and calculations based on TOF neutron diffraction

We have measured P- and S-wave velocities on two amphibolite and two gneiss samples from the Kola superdeep borehole as a function of pressure (up to 600 MPa) and temperature (up to 600 °C). The velocity measurements include compressional (Vp) and shear wave velocities (Vs1, Vs2) propagating in three orthogonal directions which were in general not parallel to inherent rock symmetry axes or planes. The measurements are accompanied by 3D-velocities calculations based on lattice preferred orientation (LPO) obtained by TOF (Time Of Flight) neutron diffraction analysis which allows the investigation of bulk volumes up to several cubic centimetres due to the high penetration depth of neutrons. The LPO-based numerical velocity calculations give important information on the different contribution of the various rock-forming minerals to bulk elastic anisotropy and on the relations of seismic anisotropy, shear wave splitting, and shear wave polarization to the structural reference frame (foliation and lineation). Comparison with measured velocities obtained for the three propagation directions that were not in accordance with the structural frame of the rocks (foliation and lineation) demonstrate that for shear waves propagating through anisotropic rocks the vibration directions are as important as the propagation directions. The study demonstrates that proper measurement of shear wave splitting by means of two orthogonal polarized sending and receiving shear wave transducers is only possible when their propagation and polarization directions are parallel and normal to foliation and lineation, respectively.     

Evaluation of density in layer compaction using SASW method

SASW test, which is non-intrusive and rapid in the field application, was used to evaluate the layer density in the roller compaction without performing the complicated inversion process. The concept of normalized shear wave velocity was introduced to minimize the effect of confinement in the density evaluation. SASW test was performed to determine the shear wave velocity of the layer, and the free–free resonant column (FF–RC) test was adopted to determine the correlation between the normalized shear wave velocity and density of the site, which is almost unique independent of confinement. Testing and data reduction procedures of both tests were briefly discussed and an evaluation procedure of the field density was proposed by effectively combining in-situ shear wave velocity determined by the SASW test with the correlation between the normalized shear wave velocity and the density determined by the FF–RC test. Finally, the feasibility of the proposed method was verified by performing a field case study at Hoengsung road construction site. Field densities determined by the proposed method matched well with those determined by sand cone tests, showing the potential of applying the proposed method in the field density evaluation.     

Influence of the ground profile on the reduction of earthquake motion at the filled man-made islands in the Kobe harbor during the 1995 Hyogoken Nambu earthquake

During the 1995 Hyogoken Nambu earthquake in Kobe, the ground motion at the filled man-made islands in the Kobe harbor was not as severe as that at the mainland. The building damage was also less compared to that on the mainland. It was found by comparative study of earthquake records that the magnitude of acceleration response on the ground surface decreases at the islands as opposed to the mainland. One dimensional effective stress analysis is adopted in this study. Input data has been generated from test results, e.g. the SPT N-value by standard penetration test and shear wave velocity V_s by PS logging. Results obtained by the analyses showed good agreement with the observed records, which is an indication of the suitability of the adopted analysis procedure. From this study, the followings are concluded. By the increase of SPT N-value of the filled layers, liquefaction near ground surface is restrained and damage modes such as ejection of water and soil can be prevented. Since the ground profile at the islands is that considerably soft filled layer and marine clay layers, etc. are present and the thickness of the surface layer is large, the initial natural period of the ground is above 1 s and the natural period is elongated further under the earthquake excitation, which is deemed to be the principal reason for the reduction of the earthquake motion at the ground surface.     

The characteristics of shear wave splitting in the source region of the April 20, 2013 Lushan earthquake

Using seismic data of the aftershocks sequence of the April 20, 2013 Lushan earthquake recorded by seismic temporary and permanent stations in the source region, with the visual inspection of particle motion diagrams, this paper preliminarily contains the polarization directions of fast shear wave and the time-delays of split shear waves at every station, and analyzes the crustal anisotropic characteristics in the source region. In the study area, the polarization direc- tions at stations BAX, TQU, L 132, L 133, L 134, and L 135 are northeast, which is consistent with the strike of Dachuan- Shuangshi fault. There are two polarization directions at MDS and L131, which are northeast and southeast. The scatter of polarization directions suggests the complex stress field around these two stations where two faults intersect. For the normalized time-delays at every station, the range is 1.02-8.64 ms/km. The largest time-delay is from L134 which is closest to the mainshock, and the smallest one is from L133. The variations in time-delays show the decreasing at stations BAX, L134, and L135 because of the stress-relaxation after earthquake.     

鄂尔多斯块体及其周缘上地幔各向异性分析研究

对布设在鄂尔多斯块体及其周缘的固定宽频带地震台网90个台站记录作远震SKS波形资料偏振分析,采用最小切向能量法求得每个台站的SKS快波偏振方向和快慢波时差,获得块体及其周缘上地幔各向异性图像,并结合1999~2007年相对鄂尔多斯块体的GPS水平地壳运动速度场,分析块体及其周缘的各向异性特征和壳幔耦合特征并重新认识块体的运动及周缘断陷带的动力学成因.分析结果认为,块体内部以零分裂为主,表现为各向同性特征;块体周缘台站延迟时间则明显大于块体中部,表现出明显的各向异性特征;快波偏振方向与地质构造走向、水平速度场方向基本一致,表明壳幔之间存在耦合,而个别台站在方向上与周围台站存在差异,可能与早期的块体活动有关.SKS横波分裂结果和现今GPS地壳水平运动场解释了鄂尔多斯块体没有旋转运动,在西南缘六盘山一带存在分叉绕流运动,汾渭断陷带的形成和发展是由于上地幔塑性物质沿挤出方向水平运动和沿裂隙向上入侵、横向扩张的综合演化结果.