煤矿开采导水裂缝发育高度及影响因素分析   总被引：2，自引：0，他引：2  

刘腾飞 《煤田地质与勘探》2013,41(3):34-37

煤矿开采形成的导水裂缝,一旦波及煤层上覆水体,则会导致水流入或溃入井下,直接威胁煤矿安全生产。在总结分析现有导水裂缝研究方法的基础上,以理论推导的方式并结合生产实际,分析了导水裂缝高度与煤层开采厚度、覆岩性质等因素的关系,明确了导水裂缝高度与采厚的平方根存在正比例关系。指出当基岩上覆有粘土冲积层或其他类似岩层时,极限曲率增量与岩层物理性质、厚度的关系对确定导水裂缝高度具有重要作用,当粘土冲积层厚度不小于2倍采厚时,粘土冲积层内下行裂缝穿透粘土层的可能性小,为特定条件导水裂缝分析提供了研究基础。   相似文献   

黏弹TTI介质中旋转交错网格高阶有限差分数值模拟   总被引：4，自引：2，他引：2       下载免费PDF全文

严红勇  刘洋 《地球物理学报》2012,55(4):1354-1365

以Carcione黏弹各向异性理论为基础,给出了适用于黏弹性具有任意倾斜对称轴横向各向同性介质(黏弹TTI介质)的二维三分量一阶速度-应力方程,采用旋转交错网格任意偶数阶精度有限差分格式求解该方程,并推导出了二维黏弹TTI介质完全匹配层(PML)吸收边界条件公式和相应的旋转交错网格任意偶数阶精度有限差分格式,实现了该类介质的地震波场数值模拟.数值模拟结果表明:该方法模拟精度高,边界吸收效果好,可以得到高精度的波场快照和合成记录;并且波场快照和合成记录能较好地反映地下介质的各向异性特征和黏弹性特征.  相似文献   

青藏高原东缘变形机制的讨论: 来自数值模拟结果的限定   总被引：5，自引：3，他引：2       下载免费PDF全文

姚琪  徐锡伟  邢会林  张微  高翔 《地球物理学报》2012,55(3):863-874

青藏高原东缘的地壳结构是两种主流青藏高原隆升模式争辩的焦点之一.中下地壳流曾经被认为是高原东缘隆升的主要构造驱动力,但是中上地壳之间低阻低速层的发现及其与2008 M_S8.0汶川地震良好的对应关系表明,高原东缘具有向东刚性挤出的可能性.然而大部分关于龙门山断裂的数值模拟仍建立在下地壳流的基础上,仅将低阻低速层作为断裂的延续或是弱化地壳物性参数的软弱层,而非能够控制块体滑动的"解耦层",也没有考虑到刚性块体变形中的断裂相互作用.本文建立了包含相互平行的龙门山断裂与龙日坝断裂的刚性上地壳模型,用极薄的低阻低速层作为块体滑动的解耦带,采用速率相关的非线性摩擦接触有限元方法,基于R最小策略控制时间步长,计算了在仅有侧向挤压力作用下,低阻低速层对青藏高原东缘的刚性块体变形和断裂活动的作用.计算结果显示,低阻低速层控制了刚性块体的垂直变形和水平变形分布特征.在侧向挤压力的持续作用下,在低阻低速层控制下的巴颜喀拉块体能够快速隆升,而缺乏低阻低速层的四川盆地隆升速度和隆升量均极小,隆升差异集中在龙门山断裂附近,使其发生应力积累乃至破裂.龙日坝断裂被两侧的刚性次级块体挟持着一起向南东方向运动,但该断裂的走滑运动分解了绝大部分施加在块体边界上的走滑量,使得相邻的龙门山次级块体的走滑分量遽然减少,也使得龙门山断裂表现出以逆冲为主,兼有少量走滑的运动性质.本文所得的这些计算结果显示了在缺乏中下地壳流,仅在低阻低速层解耦下刚性块体隆升过程及相关断裂活动,提供了青藏高原东缘刚性块体挤出的可行性,为青藏高原东缘隆升机制的研究讨论提供了重要依据.  相似文献   

Characterization of rocking shallow foundations using centrifuge model tests   总被引：1，自引：0，他引：1  

Lijun Deng  Bruce L. Kutter 《地震工程与结构动力学》2012,41(5):1043-1060

This paper presents new results of centrifuge model tests exploring the behavior of rocking shallow foundations embedded in dry sand, which provides a variety of factors of safety for vertical bearing. The results of slow (quasi‐static) cyclic tests of rocking shear walls and dynamic shaking tests of single‐column rocking bridge models are presented. The moment–rotation and settlement–rotation relationships of rocking footings are investigated. Concrete pads were placed in the ground soil to support some models with the objective of reducing the settlement induced by rocking. The behavior of rocking foundation was shown to be sensitive to the geometric factor of safety with respect to bearing failure, L_f/L_c, where L_f was the footing length, and the L_c was the critical soil‐footing contact length that would be required to support pure axial loading. Settlements were shown to be small if L_f/L_c was reasonably large. Placement of concrete pads under the edges of the footing was shown to be a promising approach to reduce settlements resulting from rocking, if settlements were deemed to be excessive and also had impacts on the energy dissipation and rocking moment capacity. A general discussion of the tradeoffs between energy dissipation and re‐centering of rocking foundations and other devices is included. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

无填充墙基础隔震RC框架在环境激励下的动力特性     

韩建平  王洪涛  李林 《地震工程与工程振动》2012,32(4):182-187

对一基础隔震钢筋混凝土框架结构在无填充墙情况下进行了环境激励下的动力测试,重点利用Hilbert-Huang变换与随机减量技术相结合的方法识别了其模态参数,并与随机子空间识别法、有理分式多项式法识别的结果进行了对比。识别结果表明在环境激励下,基础隔震结构的基本周期远小于多遇和罕遇地震工况下设计计算的基本周期;等效黏滞阻尼比很小,近乎于基础固定模型。对隔震层阻尼特性的分析表明,环境激励下可以将基础隔震结构视为经典的比例阻尼系统。进一步以识别的模态参数为基准,采用优化的方法数值反演了环境激励下该结构隔震层的实际水平等效刚度,结果表明其值为多遇地震下计算刚度取值的10.75倍。  相似文献   

层状半空间中洞室对平面SH波的放大作用   总被引：1，自引：0，他引：1  

梁建文  巴振宁 《地震工程与工程振动》2012,32(2):14-24

利用间接边界元法,求解了弹性层状半空间中洞室对入射平面SH波的放大作用问题,并以基岩上单一土层中洞室对入射平面SH波的放大作用为例进行了数值计算分析。本文模型的特点之一是考虑了层状场地的动力特性,因而更接近于实际工程;特点之二是计算精度非常高。研究表明,层状半空间中洞室对波的放大作用与均匀半空间中情况有着本质的差别;层状半空间中洞室附近地表动力响应由土层动力特性和洞室对波的散射二者共同决定。土层动力特性不仅影响洞室附近地表位移的幅值,还会影响地表位移的频谱。在土层的前几阶共振频率附近,随着基岩与土层剪切波速比的增大,土层的影响随之增大,而随着土层厚度的增加,土层的影响随之减小,并逐渐趋于均匀半空间情况。  相似文献   

也谈地壳内第二深度空间石油、天然气的形成及勘探前景     

倪祥龙  张景廉  马新民 《地球物理学进展》2012,27(2):562-574

在当前国内油气供需紧张的严峻形势下,开展"第二深度空间"的油气勘探"势在必行",也是"当务之急"."第二深度空间"的油气勘探需解决3个问题.一是油气无机成因的地球化学证据.原油、沥青、干酪根的Pb,Sr,Nd同位素示踪、原油中异常高含量的金属微量元素、原油中有机硅化合物的发现等均表明原油可以由无机反应而生成.二是油气无机成因论是可以指导油气勘探的.油气的分布与中地壳的低速、高导层的耦合表明有成因关系,中地壳的低速、高导层是油气的发生器,也是初始储层,据此可以对油气田进行预测.柴达木盆地昆北花岗岩油田的发现是一典型案例.三是"第二深度空间"的油气勘探需要地球物理方法和技术的支撑.目前第4代采集处理新理论、新方法业已提出.地球物理学家已经把深部勘探的新方法、新技术提到议事日程.总之,"第二深度空间"的油气勘探是有理论依据的,是可能的,是可操作的.发现大型、超大型油气田指日可待.  相似文献   

Correlation between plate age and layer separation of double seismic zones          下载免费PDF全文

Keliang Zhang  Dongping Wei 《地震科学（英文版）》2012,25(1):95-101

Global seismicity catalogs are sufficient for characterizing double seismic zones (DSZs) in subducting slab and facilitate to estimate layer separation without inconsistent uncertainties as local catalogs. Previous studies have shown the correlation between DSZs layer separation and plate age while correlation for those younger than ~60 Ma is suspicious. The lacking of DSZs with layer separation less than 10 km further makes it difficult to precisely estimate such correlation. Thus, we incorporate eight DSZs data determined through local seismicity into globally-determined dataset and reexamine such correlation. The best fitting results show that both a linear model and a square root of plate age can mathematically fit the layer separation well. However, it is difficult to distinguish these two models when plate age is greater than ~20 Ma since their difference is less than 2 km. However, if extrapolation is possible, both models should provide physical information that DSZs will not form if there is no subducting lithosphere. As a result, the DSZs cannot be produced until the oceanic lithospheric age becomes greater than 0.9 Ma in the square root model while the linear model gives a misleading result. As such the square root model demonstrates the relationship physically better than the linear one, it still needs further test in the future with more available data, nevertheless, our study might also provide evidence for the suggestion that the plate age is a primary control factor of the DSZs geometry as well as the subducting process which disregards any local tectonic stresses.  相似文献   

Biodegradation Studies on Acid Violet 19, a Triphenylmethane Dye,by Pseudomonas aeruginosa BCH     

Shekhar B. Jadhav  Snehal M. Yedurkar  Swapnil S. Phugare  Jyoti P. Jadhav 《洁净——土壤、空气、水》2012,40(5):551-558

Acid violet 19 (AV) belongs to the triphenylmethane (TPM) class of dyes which are potentially mutagenic or carcinogenic. However, very little studies on biodegradation of AV were reported as compared to other TPM dyes such as malachite green and crystal violet. In this study, AV was decolorized up to 98% within 30 min by Pseudomonas aeruginosa BCH. The decolorization depends on the initial dye concentration, pH, and temperature. However, the dye was decolorized under wide pH and temperature ranges with an optimum of pH 7 and 30°C. Up to 250 mg L^?1 of dye was found to be tolerated and decolorized by this strain. It showed decolorization ability for seven repeated dye addition cycles. The effect of additional carbon sources on dye decolorization was studied in which mannitol containing medium showed decolorization in 15 min. Induction in the enzyme activities of laccase, NADH‐DCIP reductase, and veratryl alcohol oxidase (VAO) indicates their involvement in AV degradation. Various analytical studies viz. UV–VIS, HPTLC, HPLC, and FTIR confirmed the biodegradation of AV by the bacterium. Based on GC‐MS analysis, a possible degradation pathway for AV was proposed. The phytotoxicity studies using Phaseolus mungo and Sorghum vulgare revealed the less toxic nature of metabolites formed after AV degradation.  相似文献   

珠江三角洲晚第四纪风化层稀土元素地球化学特征^*          下载免费PDF全文

刘春莲  杨婷婷  吴洁  夏斌  黄毅  张素青 《古地理学报》2012,14(1):125-132

珠江三角洲地区上更新统与全新统之间广泛发育1层杂色黏土,其成因多认为主要是由上更新统沉积物在末次冰盛期暴露于地表风化而成。对取自珠江三角洲3条钻孔（PRD09、PRD16和PRD17）的岩心样品分析表明,受风化作用的影响,其稀土元素含量和分异特征发生了较明显的变化。杂色黏土层的稀土总量大大低于下伏沉积物,而在邻近风化层的下伏沉积物中稀土元素却表现为明显富集,尤其是重稀土元素的富集。风化作用强度较大的PRD09孔和PRD17孔下伏沉积物中的稀土富集程度高于风化作用强度相对较小的PRD16孔。珠江三角洲在末次冰盛期时普遍发育的酸性介质条件,促进了风化层的稀土元素发生溶解和迁移。在风化过程中,由于轻、重稀土元素具有不同的溶解迁移能力和吸附能力,导致杂色黏土层的REE指标值（LREE/HREE、(La/Gd)_N和(La/Yb)_N）高于下伏沉积物。风化过程对Ce、Eu异常有一定的影响,但不十分明显,杂色黏土层的Ce、Eu异常值仅略低于下伏沉积物。  相似文献