Mechanisms of compaction of quartz sand at diagenetic conditions   总被引：5，自引：0，他引：5  

J.S Chester  S.C Lenz  F.M Chester  R.A Lang   《Earth and Planetary Science Letters》2004,220(3-4):435-451

The relative contribution of cracking, grain rearrangement, and pressure solution during experimental compaction of quartz sand at diagenetic conditions was determined through electron and optical microscopy and image analysis. Aggregates of St. Peter sand (255±60 μm diameter grain size and porosity of approximately 34%) were subjected to creep compaction at effective pressures of 15, 34.5, 70, and 105 MPa, temperatures of 22 and 150°C, nominally dry or water-saturated (pore fluid pressure of 12.5 MPa) conditions, and for times up to one year. All aggregates displayed transient, decelerating creep, and volume strain rates as low as 2×10⁻¹⁰ s⁻¹ were achieved. The intensity of fracturing and degree of fragmentation increase with volume strain and have the same dependence on volume strain at all conditions tested, indicating that impingement fracturing and grain rearrangement were the main mechanisms of compaction throughout the creep phase. The increase in fracture density and decrease in acoustic emission rate at long times under wet conditions reflect an increase in the contribution of subcritical cracking. No quantitative evidence of significant pressure solution was found, even for long-term creep at 150°C and water-saturated conditions. Comparison of our findings to previous work suggests that pressure solution could become significant at temperatures or times somewhat greater than investigated here.  相似文献   

北京市顺义城区地裂缝的成因及防治措施初探     

赵忠海 《城市地质》2002,14(3):22-25,10

本文在1／5万区域地质调查及北京市顺义区国土资源与地质环境大调查的基础上，通过野外调查，参照区域地质、物探、化探、水文及实地监测资料，对北京市顺义地区地裂缝的主要特征与变形速度进行了深入研究，初步探讨了其主要成因，认为构造活动和地下水过量超采是导致地裂缝的主要因素，并据此提出了防治意见与措施。  相似文献   

2000年云南姚安Ms6.5地震余震序列S波分裂研究   总被引：10，自引：1，他引：10  

钱晓东  李白基  秦嘉政 《中国地震》2002,18(2):157-165

本文利用云南姚安MS6 5地震后在震中附近架设的 3个三分向数字记录台站的地震资料 ,对该区S波分裂进行研究。结果表明 :① 2 36条处于横波窗内的记录S波分裂现象明显 ;②延迟时间大部份在 3 5～ 10 5ms km范围 ,平均值为 7 0ms km ;③快波偏振方向大部份在N140°E～N16 4°E范围 ,平均值为N15 2 4°E ;④快波的优势偏振方向与主震的发震断裂 (马尾菁断裂 )和余震的发震破裂方向不一致 ,而与该区的主压应力方向比较符合 ;⑤姚安地震余震序列的S波分裂是应力场控制的EDA裂隙各向异性的结果。  相似文献   

房产图中面积测算精度的探讨     

陈伟清 《测绘工程》1995,(3)

本文就《房产测量规范》所规定的解析法面积测算精度和边长丈量精度公式进行综合分析,认为两者存在精度要求上的不一致,通过对实例进行分析比较,提出一个解析法面积测算中误差的计算公式。  相似文献   

Plane failure analysis of rock slopes   总被引：1，自引：0，他引：1  

S. Sharma  T. K. Raghuvanshi  R. Anbalagan 《Geotechnical and Geological Engineering》1995,13(2):105-111

Summary Hoek and Bray (1981) gave an analytical approach for plane failure analysis for rock slopes that is limited to those slopes in which the upper slope surface is horizontal and the tension crack is vertical. An analysis is presented here which can take these factors into account. It is found that varying the angle of the upper slope from 0° to 30° causes a significant reduction in the factor of safety. Varying the tension crack from vertical to 70° only has an effect when the upper slope angle is less than 20°.  相似文献   

Transport model of buoyant metamorphic fluid by hydrofracturing in leaky rock   总被引：1，自引：0，他引：1  

Y. NAKASHIMA 《Journal of Metamorphic Geology》1995,13(6):727-736

Abstract Aqueous fluid released in metamorphism is transported upwards from depth to the Earth's surface. I propose a hydrofracturing model for the fluid transport. In the model, fluid is transported by the upward propagation of a two-dimensional vertical fluid-filled crack from a fluid reservoir (e.g. overpressured compartment under a seal) at depth to the Earth's surface; fluid is injected consecutively from the reservoir into the crack at a given (but not necessarily constant) injection rate; some of the injected fluid is lost by infiltration from the crack walls into the surrounding permeable rock. An approximate solution of the crack propagation is obtained using fluid dynamics for turbulent film flow and linear elastic fracture mechanics. The solution shows the transition from a regime in which the excess pressure of the fluid in the reservoir drives the propagation to a regime in which the buoyancy of the fluid in the crack drives the propagation. For example, if the net injection rate of H₂O is 1 m²/s, the regime transition occurs when the vertical crack length becomes 280 m; after the transition, the propagation velocity and average aperture are constant: 21 m/s and 4.8 cm. If the injection rate is lower than a critical value, hydrofracturing cannot be an effective mode for the fluid transport because of the significant fluid loss by infiltration from the crack walls into the surrounding permeable rock. Assuming a fluid-saturated crust with hydrostatic pore fluid pressure, a lower limit can be estimated for the injection rate required to transport H₂O by hydrofracturing without significant fluid loss. For example, the lower limit for transport from a depth of 15 km to the Earth's surface is estimated at 0.2 m²/s if the crustal permeability is 10^-17 m². The lower limit decreases with decreasing crustal permeability.  相似文献   

抗震变形验算中钢筋混凝土梁柱截面特性的计算     

蒋通  冯波 《世界地震工程》2001,17(1):75-81

罕遇地震作用下结构的抗震变形验算需要利用钢筋混凝土梁柱构件的三折线模型，国内外对该模型的主要参数Mc,My,α有不同的计算方法。本文介绍了几种典型的方法，并通过数值算例进行了对比计算。其中基于近似理论分析的方法与基于实验统计的经验方法之间的差异不超过20％－30％，可用于工程实践。本文还比较了各种方法的适用性。  相似文献   

孕震过程中冲流电位地电异常的理论研究   总被引：3，自引：0，他引：3       下载免费PDF全文

朱涛  赵和云 《地震学报》2001,23(4):398-406

分别计算了具有对称压力源分布的水平层状半空间介质模型和各向异性裂隙模型的地表冲流电位异常．结果表明，本文所采用的模型计算出来的地表冲流电位异常最大值的量级是合理的，其幅度最大约为几百毫伏；异常范围随地下各向异性强烈程度而变化．同时，在计算地表冲流电位异常时引入了各向异性裂隙的概念，从而从理论上解决了实际观测与理论不相符合的矛盾．   相似文献   

动态致裂过程的能量分析   总被引：2，自引：0，他引：2  

黄菊清 《岩土力学》1993,14(2):13-17

本文从能量观点出发,对裂纹形成过程进行了分析,并以此为基础,讨论了各种致裂方法的原理和特点。  相似文献   

具有孔边裂纹的岩石厚壁筒试件的破裂特征     

颜玉定  尹祥础 《华南地震》1990,10(3):9-17

用五种应力途径对由五种岩石制备的孔边有予裂纹的厚壁筒试件进行实验,研究上述条件下岩石的破裂特征。结果表明:对含径向并贯穿轴向裂纹的试件,其破裂沿裂纹方向,为典型的张开型破裂;含与定直径成45°角并贯穿轴向裂纹的试件,破裂亦呈张开型,其裂面始于裂纹前缘,但却折转约45°角与定直径近于平行;中心含与轴向成45°角的椭圆裂纹试件的破裂,仍沿裂纹面方向,为张开型与滑开型的复合破裂。  相似文献