厦门花岗岩风化层的地震扁铲侧胀(SDMT)试验研究

花岗岩风化土属于一种区域性特殊土,易扰动,其力学指标的确定多采用原位测试手段。通过对厦门地铁轨道交通1号线3个站点的典型花岗岩风化层开展地震扁铲侧胀试验,系统评价该类土的原位力学特性。结果表明,厦门花岗岩残积土土质分类为粉土-砂性土,具有似超固结特性,计算OCR值普遍大于1,排水特性属于部分排水类型;花岗岩残积土的力学性质指标对风化程度特别敏感,随埋深增加,风化程度逐渐减弱,土质分类由粉土向砂性土转化,土体水平应力减小,强度与刚度增加,剪切波速值逐渐增大,似超固结特性逐渐减弱,排水特性逐渐从非排水型向排水型过渡;利用剪切波速和土类指数I_D可以较好地对花岗岩风化土进行土质分类。地震扁铲侧胀试验（SDMT）作为一种新型改进原位测试手段,试验结果能较好反映花岗岩风化层物理力学性能,具有一定的可靠性与较广泛的适用性。论文研究结果对厦门地区花岗岩风化土地基的优化设计具有直接的指导与借鉴意义。     

上海地区扁铲侧胀试验计算地基承载力的探讨

通过对扁铲侧胀试验和试验机理的研究和对试验指数的对比分析 ,提出了用扁铲侧胀试验计算地基承载力的方法 ;利用上海地区部分重大工程中的扁铲侧胀试验数据 ,在与室内土工试验、静力触探试验及十字板剪切试验的相关分析的基础上 ,经数理统计后给出了上海地区用扁铲侧胀试验计算地基承载力的经验公式。最后 ,通过与室内土工试验、静力触探试验和十字板剪切试验计算的地基承载力对比 ,分析了本经验公式计算地基承载力的精度。研究分析表明 ,可以用扁铲侧胀试验计算地基承载力     

上海地区扁铲侧胀试验与其他原位试验结果的相关性分析

由于扁铲侧胀试验（DMT）在国内应用时间不长,如何合理地解释和应用DMT试验成果尚待进一步探讨。与其他原位试验结果进行对比分析是研究方法之一。介绍了多元回归在岩土工程相关分析中的应用。根据上海地区多个工程的扁铲侧胀试验、十字板剪切试验、标贯试验和静力触探试验的数据,通过选元分析和多元回归,得出扁铲侧胀试验与其它原位试验的相关关系,可供勘察设计相关人员参考使用。     

扁铲侧胀试验计算地基承载力

简单介绍扁铲侧胀试验,首次提出用扁铲侧胀试验计算地基承载力的方法。利用上海地区部分重大工程中的扁铲 侧胀试验数据,在与室内土工试验、静力触探试验及十字板剪切试验的试验参数相关分析的基础上,经数理统计后给出了上 海地区用扁铲侧胀试验计算地基承载力的经验公式,并对其计算精度进行了评价。     

扁铲侧胀试验在软土地基评价中的应用研究

在回顾分析国内外利用扁铲侧胀试验评价地基土性参数基础上,介绍了应用扁铲侧胀试验（DMT）和其它试验手段进行高速公路软土地基综合分析评价所取得的一些成果。根据扁铲侧胀试验结果估算的不排水抗剪强度与十字板试验结果基本一致,并能够反映土的强度随深度增长的规律,也分析了造成扁铲侧胀试验结果与室内试验结果之间差异的因素,研究结果可为扁铲侧胀试验在我国岩土工程领域的应用提供参考。     

扁铲侧胀试验在滨海沉积软土中的应用

通过运用扁铲侧胀仪(DMT)在长江入海口滨海沉积软土中进行的原位测试,获得滨海沉积软土中扁铲侧胀试验各指标参数的变化规律。扁铲侧胀试验与静力触探试验结果一致,试验结果可靠,且扁铲侧胀试验可以快速地获取侧向基床反力系数KH,为桩基础的设计提供可靠的依据。对比旁压试验结果,扁铲侧胀试验得到的KH值常常偏大。在粘土层、粘质粉土夹粉质粘土、淤泥质粉质粘土、粘质粉土、淤泥质粘土等土层中KH与真实值相差较小,可以使用,但实际应用中应同时结合规范使用;而在砂质粉土和粉砂等土层中KH与真实值相差较大,不宜使用。     

扁铲侧胀试验及其在岩土工程中应用

本文介绍了扁铲侧胀仪试验的试验方法，资料整及在国外的应用，并根据工作实践，提出了一些在岩土工程中应用扁铲侧胀仪试验的方法。     

扁铲侧胀试验在浅海钙质土力学特性评价中的应用

利用扁铲侧胀仪对海底浅层钙质土进行原位测试,能够一次获得多个评价土性的试验参数。试验表明,由于波浪循环动荷载的作用使得海底表层（深1～2 m）钙质砂的密实度比其紧邻的下部偏大,以珊瑚礁为主要胶结物的钙质土,内部具有大的孔隙或松散堆积体结构是造成海底浅层钙质砂表层与浅部土体的扁铲侧胀压力明显变化的主要原因。扁铲试验结果与现场标准贯入试验具有较好的相关性,基于Seed公式推导的适合于计算水下平均动应力比的简化公式能够较好地用于对不同地震烈度下海底浅层钙质土液化可能性的判别。     

扁铲侧胀试验与静力触探试验的成果对比分析

该文在对扁铲侧胀试验作简要介绍的基础上，利用上海地区工程实例对扁铲侧胀试验、静力触控试验这两种原位测试成果之间的关系进行了分析，探索其中存在的规律，总结出适用于本地区的经验公式，有助于扁铲侧胀试验的进一步推广应用。     

扁铲探头贯入干砂的位移特征试验研究

扁铲侧胀试验（DMT）已在国内外岩土工程勘察、地基加固效果评价等领域中得到广泛应用。DMT的测试过程在扁铲探头贯入到测试位置后进行,因此探头的贯入过程对土体造成的扰动在一定程度上将直接影响测试结果。目前关于扁铲探头的贯入机理,以及贯入过程可能引起的土体扰动及其对测试结果的影响尚未研究清楚。通过室内模型试验手段,进行扁铲探头贯入不同初始密实状态下均质干砂的试验研究,分析了探头贯入过程中产生的土体位移场分布特征。试验结果表明:扁铲探头的楔形部和膜片所在的侧胀部贯入产生的挤压作用是引起土体变形扰动的主要原因;探头楔形部的贯入过程表现为向下和向斜侧面挤压土体,竖向位移量很小,产生向两侧扩展为主的扁状位移场,而探头侧胀部的贯入过程主要表现为向两侧面水平向挤压土体,产生半椭圆状水平位移场且分布范围明显更大,同时探头侧面表现为一定的剪切作用而产生较窄范围的竖向位移场。另外,扁铲探头贯入干砂产生的位移场受砂土初始密实状态的影响较小,主要表现为探头楔形部周围的位移场分布范围随密实度增大而扩大。     

中国大陆科学钻探主孔100～2000m岩石弹性波速度：对地震深反射的约束

在常温常压条件对中国大陆科学钻CCSD主孔岩心的700样品进行了弹性波速度测量，并建立了主孔2000m的波速(Vp和Vs)连续剖面，为检验地球物理模型的合理解释提供了岩石物理学方面的宝贵资料。主孔中新鲜榴辉岩纵波速度(Vp)最大(7.86km／s)，正副片麻岩波速最小，又分别为5.53km／s和5．71km／s，榴辉岩的波速随着退变质作用的增强而明显减小。主孔2000m总平均Vp速度为6．2km／s，它与地球物理探测方法获得的大别-苏鲁造山带上地壳具有6.2-6．3km／s高速层结论是一致的。大部分岩石具有明显地震波各向异性。水饱和度使岩石纵波(Vp)速度和剪切波速度(Vs)分别增加19％和6％，而使Vp的各向异性降低3％～4％。不同岩性界面的反射系数(Rc)是产生地震反射的主要原因。金红石榴辉岩与片麻岩之间具有很高的反射系数(0.24-0．31)。韧性剪切带中糜棱岩化片麻岩和面理化榴辉岩使岩石各向异性和反射强度明显增加。岩石微裂隙与主孔原位波速变化有密切关系。饱水岩石速度(Vp和Vs)可以代表CCSD主孔原位状态的地震波速度。上述成果为本区地震反射体成因提供了重要的岩石物理性质约束。     

Petrological constraints on seismic properties of the Slave upper mantle (Northern Canada)

Modes and compositions of minerals in Slave mantle xenoliths, together with their pressures and temperatures of equilibrium were used to derive model depth profiles of P- and S-wave velocities (Vp, Vs) for composites equivalent to peridotite, pyroxenite and eclogite. The rocks were modeled as isotropic aggregates with uniform distribution of crystal orientations, based on single-crystal elastic moduli and volume fractions of constituent minerals. Calculated seismic wave velocities are adjusted for in situ pressure and temperature conditions using (1) experimental P- and T- derivatives for bulk rocks' Vp and Vs, and (2) calculated P- and T- derivatives for bulk rocks' elastic moduli and densities. The peridotite seismic profiles match well with the globally averaged IASP91 model and with seismic tomography results for the Slave mantle. In peridotite, an observed increase of seismic wave velocities with depth is controlled by lower degrees of chemical depletion in the deeper upper mantle. In eclogite, seismic velocities increase more rapidly with depth than in peridotite. This follows from contrasting first-order pressure derivatives of bulk isotropic moduli for eclogite and peridotite, and from the lower compressibility of eclogite at high pressures. Our calculations suggest that depletion in cratonic mantle has a distinct seismic signature compared to non-cratonic mantle. Depleted mantle on cratons should have slower Vp, faster Vs and should show lower Poisson's ratios due to an orthopyroxene enrichment. For the modelled Slave craton xenoliths, the predicted effect on seismic wave velocities would be up to 0.05 km/s.     

Vp/Vs Anisotropy and Implications for Crustal Composition Identification and Earthquake Prediction

The ratio of P- to S-wave velocities (Vp/Vs) is regarded as one of the most diagnostic properties of natural rocks. It has been used as a discriminant of composition for the continental crust and provides valuable constraints on its formation and evolution processes. Furthermore, the spatial and temporal changes in Vp/Vs before and after earthquakes are probably the most promising avenue to understanding the source mechanics and possibly predicting earthquakes. Here we calibrate the variations in Vp/Vs in dry, anisotropic crustal rocks and provide a set of basic information for the interpretation of future seismic data from the Wenchuan earthquake Fault zone Scientific Drilling (WFSD) project and other surveys. Vp/Vs is a constant (φ0) for an isotropic rock. However, most of crustal rocks are anisotropic due to lattice-preferred orientations of anisotropic minerals (e.g., mica, amphibole, plagioclase and pyroxene) and cracks as well as thin compositional layering. The Vp/Vs ratio of an anisotropic rock measured along a selected pair of propagation-vibration directions is an apparent value (φij) that is significantly different from the value for its isotropic counterpart (φ0). The usefulness of apparent Vp/Vs ratios as a diagnostic of crustal composition depends largely on rock seismic anisotropy. A 5% of P- and S-wave velocity anisotropy is sufficient to make it impossible to determine the crustal composition using the conventional criteria (Vp/Vs<1.756 for felsic rocks, 1.756l.944 fluid-tidied porous/fractured or partially molten rocks) if the information about the wave propagation-polarization directions with respect to the tectonic framework is unknown. However, the variations in Vp/Vs measured from borehole seismic experiments can be readily interpreted according to the orientations of the ray path and the polarization of the shear waves with respect to the present-day principal stress directions (I.e., the orientation of cracks) and the frozen fabric (I.e., foliation and lineation).     

横波地震基本理论的研究

The people have highly attached importance to the technipues of S-wave seismics. It is basic
premise of S一wave exploration or combining S-wave and P-wave study the basic theory for S-wave seismics. In the basic theory，especially，seismic-wave velocities(V_p,V_s) and its ratio(V_p,V_s) must be studied.
     

Tomographic models and seismotectonics of the Reggio Emilia region, Italy

The aim of this study is to define the Vp and Vp/Vs structure of the fault zone ruptured by the M_L 5.1 earthquake of October 15, 1996 which occurred near Reggio Emilia (central-northern Italy). A 1-month-long seismic sequence followed the mainshock and occurred in a small region along the outer border of the northern Apenninic belt, at depth ranging between 10 and 17 km. P- and S-wave arrival times from 304 aftershocks recorded by two local dense seismic arrays installed in the epicentral region have been inverted to obtain one- and three-dimensional velocity models by using state of the art local earthquake tomographic techniques. Velocity models and aftershock relocation help us to infer the seismotectonic of the region. Earthquakes originated along a NW-dipping backthrust of a NE-trending main thrust, composing the western part of the broad Ferrara Arc. A main high Vp and high Vp/Vs region delineates a pop-up structure in the center of the area. The high Vp/Vs within the pop-up structure supports the presence of a zone with increased pore pressure. The hypocentral depth of both mainshock and aftershocks is greater than those usually found for the main seismogenic regions of the Apenninic belt. P-wave velocity values in the seismogenic area, obtained by tomography, are compatible with rocks of the Mesozoic cover and suggest that seismicity occurred within the Mesozoic units stack at present by compressional tectonics.     

Deformation microstructures of olivine and chlorite in chlorite peridotites from Almklovdalen in the Western Gneiss Region,southwest Norway,and implications for seismic anisotropy

Chlorite peridotites from Almklovdalen in southwest Norway were studied to understand the deformation processes and seismic anisotropy in the upper mantle. The lattice preferred orientation (LPO) of olivine and chlorite was determined using electron backscattered diffraction (EBSD)/scanning electron microscopy. A sample with abundant garnet showed [100] axes of olivine aligned sub-parallel to lineation, and [010] axes aligned subnormal to foliation: A-type LPO. Samples rich in chlorite showed different olivine LPOs. Two samples showed [001] axes aligned sub-parallel to lineation, and [010] axes aligned subnormal to foliation: B-type LPO. Two other samples showed [100] axes aligned sub-parallel to lineation, and [001] axes aligned subnormal to foliation: E-type LPO. Chlorite showed a strong LPO characterized by [001] axes aligned subnormal to foliation with a weak girdle subnormal to lineation. Fourier transform infrared (FTIR) spectroscopy of the specimens revealed that the olivines with A-type LPO contain a small amount (170 ppm H/Si) of water. In contrast, the olivines with B-type LPOs contain a large amount (340 ppm H/Si) of water.

The seismic anisotropy of the olivine and chlorite was calculated. Olivine showed Vp anisotropy of up to 3.8% and a maximum Vs anisotropy of up to 2.7%. However, the chlorite showed a much stronger Vp anisotropy, up to 21.1%, and a maximum Vs anisotropy of up to 31.7%. A sample with a mixture of 25% of olivine and 75% of chlorite can produce a Vp anisotropy of 14.2% and a maximum Vs anisotropy of 22.9%. Because chlorite has a wide stability field at high pressure and high temperature in the subduction zone, the strong LPO of chlorite can be a source of the observed trench-normal or trench-parallel seismic anisotropy in the mantle wedge as well as in subducting slabs depending on the dipping angle of slab in a subduction zone where chlorite is stable.     

Crustal and upper mantle S-wave velocity structures across the Taiwan Strait from ambient seismic noise and teleseismic Rayleigh wave analyses

Although orogeny tapers off in western Taiwan large and small earthquakes do occur in the Taiwan Strait, a region largely untouched in previous studies owing mostly to logistical reasons. But the overall crustal structure of this region is of particular interest as it may provide a hint of the proto-Taiwan before the orogeny.By combining time domain empirical Green’s function (TDEGF) from ambient seismic noise using station-pairs and traditional surface wave two-station method (TS) we are able to construct Rayleigh wave phase velocity dispersion curves between 5 and 120 s. Using Broadband Array in Taiwan for Seismology (BATS) stations in Taiwan and in and across the Strait we are able to derive average 1-D Vs structures in different parts of this region. The results show significant shear velocity differences in the upper 15 km crust as expected. In general, the highest Vs in the upper crust observed in the coastal area of Mainland China and the lowest Vs appears along the southwest offshore of the Taiwan Island; they differ by about 0.6–1.1 km/s. For different parts of the Strait, the upper crust Vs structures are lower in the middle by about 0.1–0.2 km/s relative to those in the northern and southern parts. The upper mantle Vs structure (Moho – 150 km) beneath the Taiwan Strait is about 0.1–0.3 km/s lower than the AK135 model. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island. The inversion of seismic velocity structures using shorter period band dispersion data in the sea areas with water depth deeper than 1000 m should take water layer into consideration except for the continental shelves.     

Research of reservoir watershed fine zoning and flood forecasting method

In the present study, a set of correlation relations between standard penetrations tests (SPT-N values) and shear wave velocity (Vs) for different categories of soils is developed for Dholera region, Gujarat state, Western India. Shear wave velocities were measured using multichannel analysis of surface wave (MASW at 42 sites) and by PS logging (at 16 sites). SPT-N values were taken in total 87 geotechnical boreholes at depth interval of 3 m. Seismic site classification is done as per National Earthquake Hazards Reduction Program of the USA. Total 336 pairs of SPT-N values and Vs data at different depths are used to develop the regression correlation between uncorrected SPT-N value and Vs and compared with the results of other workers from India and worldwide for all soils type. It is found that regression correlations developed for clay and all soils are almost similar to each other, for sand, the coefficient value is less and for silt, it is higher. The new regression equation gives good prediction performance. The present correlation can be used for the seismic hazard study for the study area and also for the other areas having similar soil strata using a process of validation.     

Three dimensional velocity structure of the Koyna-Warna region using local earthquake tomography

A dense seismic network (～100 stations) was operated in the Koyna-Warna region from January 2010 to May 2010, that allow us to collect 400 high-quality local earthquake data of magnitude less than 4. In this region, the fault structure and tectonic setting that accommodate the induced seismicity is not well understood. To investigate the seismotectonics of the region, we have inverted 7826 P- and 7047 S-P arrival times for 3-D Vp and Vp/Vs tomographic models along with hypocenters parameters in the region. Although, Dixit et al. (2014) have performed 3-D local earthquake tomography with double-difference tomography code using catalog differential time data. In this paper, Simulps14 code on the same data set is applied. For better approach P arrival time and S-P travel times are inverted directly for Vp, Vp/Vs variations and earthquake locations. High Vp ～5.9 to 6.5 and low to high Vp/Vs ～1.69-1.74 imaged in the hypocenter region. These features interpreted as a fluid bearing rock mass under high pore pressure. It is also observed that below the trap basement form a local topography depression between the Koyna and Warna Reservoirs. To the South of the Warna reservoir, intense seismic activity defines a major cluster of ～ 5 km width at 3 to7 km deep, located under the trap, where the basement is deepening. Such regions are inferred to be associated with the seismically active faults zones. The obtain velocity anomalies are reliable down to a depth of 10 km. This is also confirmed by the analysis of three resolution parameters viz. Hit count, Derivative Weight sum (DWS) and Resolution Diagonal Elements (RDE).     

An insight into the unrest phenomena at the Campi Flegrei caldera from Vp and Vp/Vs tomography

High resolution Vp and Vp/Vs tomography of the Campi Flegrei caldera is obtained using active and passive seismic data. We find a continuous ring of high Vp anomaly that defines the caldera rim associated to the last collapse. A sharp Vp/Vs decrease is observed between 2 and 4 km depth, suggesting the absence of magmatic fluids and the presence of rock volumes with over‐pressured gas within the source region of uplift. Atmospheric water penetrating within the caldera and deep CO₂ fluids are presumably heated by a magmatic body located at depth greater than 4 km nested within the limestone layer. Along the fractures bordering the shallow high Vp rim, deep gas and CO₂ fluids up‐raise and are released in the Pozzuoli solfatara. We hypothesize that the past unrest episode is more likely due to pressure changes within the shallow geothermal reservoir located at the top of the magma intrusion.