多宝山矿田的地面波谱研究及其在铜矿预测中的应用

根据矿田内岩矿地质波谱与ＴＭ图象亮度的线性相关关系，论述了多宝山铜矿田内矿床的地面波谱特征，地空相关模型及ＴＭ数据的地空相关分析方法，在此基础上讨论了其在铜矿预测中的应用效果。     

滦县地磁场井下观测系统抗干扰效果

近距离铁磁性物质干扰(农田耕作、基建等)、直流供电干扰(高压直流输电、地电阻率观测等)是地磁场地面观测的主要干扰方式。在滦县地震台布设地磁场井下观测系统,检验井下观测的抗干扰效果,结果发现,地磁场井下观测可抑制近距离铁磁性物质干扰,但无法抑制直流供电干扰(可通过避让一定距离解决),该分析结果为未来地震监测手段的选取提供技术参考指标和依据。     

Geomorphic Evidence for and Rate of Sinistral Strike-slip Movement Along Northwest-trending Faults in Chaoshan Plain

Two sets of active faults,northwest-and northeast-trending faults,are developed in the Chao-shan Plain of East Guangdong.After detailed interpretation of aerophotos,we have found outthat there is the clear phenomenon of sinistral dislocation of drainage system on the Huang-gang-shui fault and part of Fengshun-Shantou fault.Field investigation confirmed that the geo-morphic bodies along the two faults have undergone displacement.Large-scale topographicmapping was made at three displaced sites and samples for age dating were collected from thegeomorphic booies.Calculation indicates that the average rate of sinistral strike-slip movementin the Holocene time amounts to 1.11±0.09～2.69±0.24mm/a along the Huanggangshuifault and 3.26±0.26mm/a along the Fengshun-Shantou fault.These two more active NW-trending faults extend into sea area,where they intersect the NE-trending strongly active Nius-han Island-Xiongdi Isle-Nanpeng Isles fault at a depth of 40～50m in water.The intersection isa location favorable fo     

Field study of monotonic and cyclic lateral behaviour of piles in soft soils improved with and without vacuum preloading

Acta Geotechnica - Project Oufei is the largest individual reclamation project in Wenzhou city, China, and the main infrastructure consists of seawalls, sluices and separation dikes. These...     

高压旋喷桩单桩承载力分析

高压喷射注浆于1968年首创于日本。我国于20世纪70年代初相继引进并开始研究高压喷射注浆技术。目前,高压旋喷工艺应用最为广泛,工艺技术最为成熟。对旋喷桩成桩质量及单桩承载力进行研究分析,为旋喷桩在地基与基础工程、水利水电工程、止水、加固工程中的应用提供设计参考依据。该试验在陕西省延安市某建成小区内选三个试验点,按不同旋喷桩施工工艺成桩,通过对桩身完整性检测、单桩承载力试验,分析旋喷桩成桩质量及单桩承载力。     

Entrepreneurship, ethnicity and local contexts: Hispanic entrepreneurs in three U.S. southern metropolitan areas

Previous research suggests that entrepreneurship can provide ethnic minorities a springboard for economic advancement and social integration. However, self-employment rates vary significantly among ethnic groups, between men and women, and in different places. The prevailing literature suggests that personal characteristics, including human capital attributes, ethnic networking, institutional regulations, societal structures and discrimination, all contribute to the differential ethnic entrepreneurship rates. However, very few recent studies have analyzed how different urban socio-economic contexts influence this process. Using the 2000 Public Usable Microdata Samples (PUMS), this study examines how Hispanic entrepreneurs perform in three different metropolitan areas in the US South. The results show that the ethnic diversity, history of immigration, and the economic structure in each local area have provided different opportunities and challenges for Hispanics to start up and maintain their own businesses. This study suggests that the process of economic incorporation of ethnic minorities and immigrants depends significantly on the institutional capacity and social, cultural and political resources of local communities.     

The strength and fractal dimension characteristics of alum–kaolin flocs

Flocs generated by various shear forces exhibit different characteristics of size, strength and structure. These properties were investigated by employing a continuous optical monitoring and a microscope with CCD camera to directly monitor aggregation under six different shear intensities. The floc structure was characterized by the fractal dimension. The results showed that the flocculation index (FI) decreased from 1.16 at 20 rpm to 0.25 at 250 rpm and the floc size decreased from 550 μm to 150 μm, meantime, the FI value showed a good correlation with floc size. In order to determine the floc strength, two methods were used. One was the strength factor, ranging from 18.3% to 62.5%, calculated from FI curve, and the other was a theoretical value between 0.005 N/m² and 0.240 N/m², estimated by calculation. The floc strength increased with the G value in both cases. Furthermore, the fractal dimension increased with G and its value was between 1.30 and 1.63. The relation between fractal dimension and strength was also obtained.     

Climatic change during the last 4000 years in the southern Tarim Basin,Xinjiang, northwest China

In this study, a ca. 4000 cal. yr ancient lacustrine (or wetland) sediment record at the southern margin of Tarim Basin is used to reconstruct the history of climate change. Six radiocarbon dates on organic matter were obtained. δ¹⁸O and δ¹³C of carbonate, pollen and sediment particle size were analysed for climate proxies. The proxies indicate that a drier climate prevailed in the area before ca. 1010 BC and during period 1010 BC–AD 500 climate then changed rapidly and continuously from dry to moist, but after about AD 500 climate generally shows dry condition. Several centennial‐scale climatic events were revealed, with the wettest spell during AD 450–550, and a relatively wetter interval between AD 930–1030. Pollen results show that regional climate may influence human agricultural activities. Spectral analysis of mean grain size (MGS) proxy reveals statistically pronounced cyclic signals, such as ca. 200 yr, ca. 120 yr, ca. 90 yr, ca. 45 yr and ca. 33 or 30 yr, which may be associated with solar activities, implying that solar variability plays an important role in the decadal‐ and centennial‐scale climate variations in the study area. Copyright © 2007 John Wiley & Sons, Ltd.     

Geology and Metallogenesis of the Sawayaerdun Gold Deposit in the Southwestern Tianshan Mountains, Xinjiang, China

The Sawayaerdun gold deposit, located in Wuqia County, Southwest Tianshan, China, occurs in Upper Silurian and Lower Devonian low‐grade metamorphic carbonaceous turbidites. The orebodies are controlled by a series of NE‐NNE‐trending, brittle–ductile shear zones. Twenty‐four gold mineralized zones have been recognized in the Sawayaerdun ore deposit. Among these, the up to 4‐km‐long and 200‐m wide No. IV mineralized zone is economically the most important. The average gold grade is 1–6 g/t. Gold reserves of the Sawayaerdun deposit have been identified at approximately 37 tonnes and an inferred resource of 123 tonnes. Hydrothermal alteration is characterized by silicification, pyritization, arsenopyritization, sericitization, carbonatization and chloritization. On the basis of field evidence and petrographic analysis, five stages of vein emplacement and hydrothermal mineralization can be distinguished: stage 1, early quartz stage, characterized by the occurrence of quartz veins; stage 2, arsenopyrite–pyrite–quartz stage, characterized by the formation of auriferous quartz veinlets and stockworks; stage 3, polymetallic sulfide quartz stage, characterized by the presence of auriferous polymetallic sulfide quartz veinlets and stockworks; stage 4, antimony–quartz stage, characterized by the formation of stibnite–jamesonite quartz veins; and stage 5, quartz–carbonate vein stage. Stages 2 and 3 represent the main gold mineralization, with stage 4 representing a major antimony mineralization episode in the Sawayaerdun deposit. Two types of fluid inclusion, namely H₂O–NaCl and H₂O–CO₂–NaCl types, have been recognized in quartz and calcite. Aqueous inclusions show a wide range of homogenization temperatures from 125 to 340°C, and can be correlated with the mineralization stage during which the inclusions formed. Similarly, salinities and densities of these fluids range for each stage of mineralization from 2.57 to 22 equivalent wt% NaCl and 0.76 to 1.05 g/cm³, respectively. The ore‐forming fluids thus are representative of a medium‐ to low‐temperature, low‐ to medium‐salinity H₂O–NaCl–CO₂–CH₄–N₂ system. The δ³⁴S_CDT values of sulfides associated with mineralization fall into a narrow range of ?3.0 to +2.6‰ with a mean of +0.1‰. The δ¹³C_PDB values of dolomite and siderite from the Sawayaerdun gold deposit range from ?5.4 to ?0.6‰, possibly reflecting derivation of the carbonate carbon from a mixed magmatic/sedimentary source. Changes in physico‐chemical conditions and composition of the hydrothermal fluids, water–rock exchange and immiscibility of hydrothermal fluids are inferred to have played important roles in the ore‐forming process of the Sawayaerdun gold–antimony deposit.     

Study on wetting deformation characteristics of coarse granular materials and its simulation in core-wall rockfill dams

The wetting deformation of coarse granular materials is often considered to be an important cause of the core wall rockfill dam cracks during impounding. By analyzing existing research results, this paper proposes a hyperbolic relationship between the wetting axial strain and wetting stress level and puts forwards a warped surface relationship among spherical stress, shear stress, and the ratio of wetting volumetric strain to wetting axial strain. To illustrate its practicability, the wetting strain model's parameter determination process is introduced and the rockfill materials wetting parameters are determined using the triaxial wetting test data. Moreover, the collapse settlement of Guanyinyan rockfill dam during first impounding is numerically simulated using the proposed method to calculate rockfill wetting deformation and verified by field measurements and monitoring data. The results show that the calculative method of wetting deformation proposed in this paper is reasonable and practical; the wetting deformation of upstream rockfill materials would cause an adverse deformation trend, which may lead to crack occurrence at the upstream slope and dam crest; and the Guanyinyan rockfill dam cracks on the top of junction mainly caused by the wetting deformation of upstream rockfill.