External seismic stability of vertical geosynthetic-reinforced soil walls using pseudo-static method     

Xiaobo Ruan  Shulin Sun 《Acta Geotechnica》2014,9(6):1085-1095

Analysis of external stability of vertical geosynthetic-reinforced soil (GRS) walls is very important in the seismic prone zone. The scope of this paper is to obtain required minimum reinforcement length, L _min, for external seismic stability of vertical GRS walls by pseudo-static limit equilibrium method. Then, L _min can be calculated to resist sliding, eccentricity, and bearing capacity failure modes. The parameters considered include both horizontal and vertical seismic coefficients (k _h and k _v ), surcharge load (q), wall height (H) and the properties of retained backfill, GRS, and foundation soil. Results show that L _min against sliding failure mode, L _min,S , increases more quickly than that against the other two failure modes with the increase in k _h , q, or unit weight of retained backfill, γ _b , while L _min,S decreases more quickly than that against the other two failure modes with increase in friction angle of retained backfill, ? _b , or unit weight of GRS, γ _r . For the different failure modes, the effect of k _v on L _min is not identical with the change of k _h , and in addition, L _min/H will tend to remain unchanged with the increase in H. In general, L _min against bearing capacity failure mode, L _min,BC, is larger than L _min against the other two failure modes. However, L _min,BC will be less than L _min against eccentricity failure mode, L _min,E , for k _h exceeding 0.35, or friction angle of foundation soil, ? _f , exceeding 37°, and L _min,BC will also be less than L _min,S for friction angle of GRS, ? _r , being no more than 26°.  相似文献   

Availability of coastal groundwater discharge as an alternative water resource in a large-scale reclaimed land,Korea     

Byung Sun Lee  Sung-Ho Song  Jin Sung Kim  Jae Yeon Um  Kyoungphile Nam 《Environmental Earth Sciences》2014,71(4):1521-1532

This study was conducted to identify the availability of coastal groundwater discharge (CGD), subsurface fluids flowing from inland through the coastal area to sea, as an alternative water resource for a large-scale reclaimed land. The behaviors of stable isotopes indicated that groundwater originated from inland precipitation and traveled as CGD along the coast line. Most of the groundwater samples collected from domestic wells installed along the old coast line were considered to be relatively fresh from the correlation analysis among chemical constituents. The average electrical conductivity (EC) values of the samples were identified as averaging 1,125–1,297 μS cm^?1, corresponding to appropriate crop growth. A weathered-rock layer in a small catchment within the reclaimed land was proved to be a main CGD pathway, with electrical resistivity anomalies ranging from 7 to 14 Ω m. Five monitoring wells were placed in this catchment to delineate the occurrence of CGD. Long-term vertical EC profiling results for the monitoring wells indicated that CGD occurs within a depth of 30 m below the ground surface. Annual monitoring data for groundwater level and EC demonstrated that the water quality of CGD was improved by introducing fresh terrestrial groundwater. A remarkable improvement in water quality (EC decrease of 900–1,600 μS cm^?1) of CGD was observed during the saline water pumping test that explains how CGD could be an alternative water resource for the reclaimed land.  相似文献   

Mercury-binding forms in coals and their geological provenances in coals of different types     

Dun Wu  Guijian Liu  Ruoyu Sun  Shancheng Chen 《Environmental Earth Sciences》2014,71(12):4989-4995

Mercury (Hg) is an element of environmental and geological significance. Quantification of different Hg-binding forms is crucial to understand geological Hg provenances and associated geochemical processes during coal formation. In this study, seven coal samples were selected, according to coal rank (i.e., middle volatile bituminous, C-3; low volatile bituminous, C-2; anthracite, C-1), chemical anomalies (high S coal, IBC-105; high Cl coal, C22650) and sampling environment (fresh coal, LH; weathered coal LHW), to determine their Hg-binding forms using well-established sequential extraction procedures coupled with sink–float experiment. In the thermally metamorphosed samples C-1 and C-2, a comparative enrichment of total Hg relative to C-3 is observed. Silicate- and organic-bound Hg are the dominant Hg-binding forms in C-1, suggesting possible Hg sources from magma silicate and secondary Hg enrichment by adsorption. Sulfide- and organic-bound Hg are the most abundant Hg-binding forms in IBC-105, whereas only organic-bound Hg dominates in CC22650. Weathering processes are suggested to transform the abundant sulfide-bound Hg in LH to silicate- and organic-bound Hg in its weathering product LHW.  相似文献   

Statistical analysis of hydrochemistry of groundwater and its implications for water source identification: a case study   总被引：1，自引：0，他引：1  

L. H. Sun 《Arabian Journal of Geosciences》2014,7(9):3417-3425

Hydrochemistry of groundwater is important for inrush water source identification in coal mines. For determining the source of inrush water from the 8101 working face in the Wolonghu coal mine, Northern Anhui Province, China, a total of 22 groundwater samples from three aquifer systems (loose layer—LA, coal bearing sandstone—CA, and the underlying limestone—TA), and eight samples from the 8101 working face were collected for analyzing major ion concentrations. The results suggest that major ion concentrations of the aquifer systems were different from each other, and they can be subdivided into Na–HCO₃, Na–SO₄, and Ca–SO₄ types. Factor analysis indicates that their chemical compositions are mainly originated from two kinds of contributions: dissolution of soluble minerals (e.g., calcite, dolomite, and gypsum) and weathering of silicate minerals (e.g., plagioclase). Plots of factor scores and cluster analysis imply that LA was connected with CA, whereas TA was an isolated aquifer system. Moreover, the source of 8101 working face water was finally determined to be LA by using discriminant analysis.  相似文献   

南方震旦系灯影组热液白云岩化及其对储层形成的影响研究——以黔中隆起为例   总被引：1，自引：0，他引：1       下载免费PDF全文

朱东亚  金之钧  孙冬胜  彭勇民  张荣强  袁玉松 《地质科学》2014,(1):161-175

我国南方地区,特别是四川盆地震旦系灯影组是我国当前高演化天然气勘探的热点,以黔中隆起为例,新揭示了其中发育的热液白云岩化现象,并探讨了其对储层形成的影响。研究区灯影组白云岩溶蚀孔洞或裂缝中见有白云石、石英、沥青充填,其中一种充填的粗晶白云石具有弯曲晶面、波状消光特征,在岩石学特征上初步反映热液成因。地球化学特征进一步揭示了这种热液成因。不同采样位置热液白云石样品中流体包裹体均一温度平均为157.5 ℃～205.8 ℃,最高为253.5 ℃。热液白云石具有较轻的氧同位素组成,δ¹⁸O_PDB 位于 -15.3‰～-8.6‰之间,平均值为 -11.2‰;较高的⁸⁷Sr/⁸⁶ Sr比值（0.709 445～0.713 131）,其平均值为0.710 843,在稀土元素组成上,热液白云石具有典型的Eu正异常的特点,δEu值为1.11～7.46,平均值为2.37。因此,灯影组热液白云石发育。热液活动对储层形成具有积极影响,主要体现在对充填在早期岩溶孔洞和构造裂缝中的白云石产生了溶蚀作用,溶蚀孔中见沥青充填,反映为油气运移通道和聚集空间。因此,热液溶蚀改造作用对我国南方地区震旦系灯影组及下古生界碳酸盐岩储层发育可能具有重要意义,值得加强探索研究。  相似文献   

A Study on Crack Damage Stress Thresholds of Different Rock Types Based on Uniaxial Compression Tests   总被引：7，自引：3，他引：4  

Lei Xue  Siqing Qin  Qiang Sun  Yuanyuan Wang  Lee Min Lee  Weichao Li 《Rock Mechanics and Rock Engineering》2014,47(4):1183-1195

When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress σ _cc, crack initiation stress σ _ci, crack damage stress σ _cd, and uniaxial compressive strength σ _ucs; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress σ _cd, its threshold, and a possible relationship between σ _cd and the uniaxial compressive strength. The σ _cd of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in σ _cd /σ _ucs between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average σ _cd /σ _ucs resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of σ _cd /σ _ucs for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on σ _cd /σ _ucs. The ratio σ _cd/σ _ucs could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.  相似文献   

芦山地震同震和震后地表形变及重力变化的理论模拟          下载免费PDF全文

邓明莉  孙和平  徐建桥  祝意青 《地球科学》2014,39(9):1373-1382

为了研究芦山地震的孕震过程和震源区的长期构造过程以及解释实测的震后形变和重力资料, 采用分层介质模型, 利用数值模拟的方法, 考虑区域流变系数, 计算了地震引起的地表同震、震后的形变和重力变化以及区域内部分GPS与重力连续观测台站的震后形变和重力变化的时间序列.结果表明: 芦山地震的地表同震形变显示出发震断层明显的逆冲特性; 粘弹性松弛效应引起的震后地表形变和重力变化比同震形变和重力变化的范围明显扩大, 但随着粘滞系数的增加, 变化量明显减小; 观测台站的震后变化时变曲线显示震后形变和重力变化在震后50 a间变化显著, 100 a后基本平缓, 趋于稳定; 模拟计算的GPS台站中除了MEIG台和MYAN台以外, 其余台站的震后观测必须考虑粘弹性松弛的影响.   相似文献   

河北承德大庙铁矿床地质构造特征与找矿预测   总被引：2，自引：0，他引：2  

陈正乐  陈柏林  李厚民  杜维河  李立兴  韩凤彬  王永  孙岳  吴玉  张文高 《地质学报》2014,88(12):2339-2350

大庙斜长岩杂岩体位于华北克拉通北缘,是我国唯一岩体型斜长岩杂岩体,赋存了丰富的Fe-Ti-P矿床.对该杂岩体的岩石学、矿床成因研究已经较为深入,但是矿田构造研究较为薄弱.本文主要从大庙矿床地质特征分析入手,通过控矿构造分析和成矿期构造应力场的恢复,结合成矿特征分析,建立大庙矿床找矿预测模型,开展找矿预测.在大庙杂岩体内,先后找到了大庙、黑山、马营和罗锅子沟等中—大型矿床,它们都具有典型的岩浆矿床特征,具有岩浆熔离、分异和贯入式成矿特征;系统的野外地质调查和翔实的构造解析表明,大庙杂岩体的侵位受控于EW向隆化-平泉和大庙-红石砬子的断裂构造,杂岩体内NE和NW向两组断裂构造控制了杂岩体内铁-铁磷矿带的发育,NS向断裂则主要为成矿后构造,往往错断了铁矿体.在黑山矿区,野外观测发现含矿苏长岩利用了固结斜长岩中发育的节理,呈脉状贯入,在节理交汇部位铁矿体变大变富;通过节理和矿脉走向的详细测量和吴氏网统计分析,推测大庙矿区成矿期含矿苏长岩的侵位受控于区域上近似NS向的挤压应力作用.根据大庙杂岩体的岩浆侵位时代、岩相-矿体的接触关系、控矿构造和成矿特征,复原了大庙杂岩体的成矿-构造演化过程:最早期区域构造活动控制了斜长岩的侵位,没有发生矿化;苏长岩的侵位,伴随发生了早期的结晶分凝式矿化;块状苏长岩的侵位导致了晚期的熔离-贯入式矿化的形成;成矿期后,大庙杂岩体还经历了多期次的构造变动、抬升和剥蚀.在此基础上,建立了大庙铁矿床的找矿预测模型,并系统分析了大庙矿田不同矿区的深部和外围的找矿潜力,认为黑山和大庙矿区的深部、黑山矿区东侧和北侧、大庙杂岩体的东部边缘可能被中生界覆盖的区域等地段都具有很好的找矿空间,大庙矿区铁矿资源潜力巨大.  相似文献   

新疆二红洼镁铁—超镁铁岩体橄榄石成因及其对硫化物熔离的指示     

孙涛  钱壮志  张瑞  张江江  姜超  杨素红  王若梅 《地质学报》2014,88(8):1494-1503

二红洼岩体位于新疆东天山黄山镁铁—超镁铁岩带的西段,地表由南、北两个小岩体组成,北岩体出露面积约1.42km2,呈北东—南西向展布;南岩体在呈椭圆形,出露面积约为6.25km2。岩体可分为两个侵入期次:第一侵入期次岩性为(含长)二辉橄榄岩和橄榄辉长岩,第二侵入期次岩性为辉长苏长岩和淡色辉长岩,辉长苏长岩侵入于第一期次形成的含长二辉橄榄岩和橄榄辉长岩中。岩体橄榄石Fo值在80.9~89.7之间,为贵橄榄石;Ni含量变化范围较大,主要集中在102.19×10-6~4319.66×10-6之间。岩体母岩浆MgO含量为10.3%,FeO含量为10.8%;回归计算结果显示二红洼岩体的原始岩浆中MgO含量为15.73%,FeO含量为10.71%。在橄榄石的结晶过程中母岩浆达到硫饱和,并发生有硫化物的熔离作用;橄榄石与硫化物的晶出质量比(橄榄石:硫化物)为50~100∶1。通过岩石学、矿物学特征以及模拟计算结果表明,二红洼岩体具有形成铜镍矿床的基本条件,但是岩体在深部岩浆房已经达到硫饱和并发生了硫化物的熔离作用,导致母岩浆中亏损Ni、Cu等成矿元素,未能形成工业矿体;在以后找矿勘探中,需要寻找早期硫化物熔离所形成的那部分硫化物熔体,并进一步寻找成矿富集的有利地段。  相似文献   

青海都兰盐沼区地震采集关键技术研究     

张志林  刘斌  何京国  高芦潞  刘丽娟  孙俪 《物探与化探》2014,(3):510-515

都兰盐沼区地表覆盖大量盐池、盐湖,近地表结晶互层多而厚,呈现速度反转现象,致使地震资料品质不高。笔者通过对都兰地区近地表介质地震响应特征的深入分析,重点对结晶互层和串珠孔穴进行模拟分析,应用实际地震资料验证了近地表结晶互层的吸收衰减规律。对该区近地表分层、井深设计以及观测系统变观优化技术进行了深入的探讨,取得了相应的采集技术系列,并在实际采集应用中取得了很好的效果,成功地解决了都兰盐沼区地震采集难题。  相似文献