Engineering geological studies and tunnel support design at Sulakyurt dam site, Turkey   总被引：2，自引：0，他引：2  

H. Basarir 《Engineering Geology》2006,86(4):225-237

This paper presents the results of engineering geological investigations and tunnel support design studies, carried out at the Sulakyurt dam site, northeast of Ankara, Turkey. The Sulakyurt dam will be used for flow control and water storage for irrigation projects. Studies were carried out both in the field and the laboratory. Field studies include engineering geological mapping, intensive discontinuity surveying, core drilling and sampling for laboratory testing. The diversion tunnel will be driven in rock mass, consisting of granite and diorite. Empirical, analytical and numerical methods were combined for safe tunnel design. Rock mass rating (RMR), Rock mass quality (Q) and Geological strength index (GSI) systems were used for empirical rock mass quality determination, site characterization and support design. The convergence–confinement method was used as analytical method and software called Phase², a 2D finite element program, was utilized as numerical method. According to the results acquired from the empirical, analytical and numerical methods, tunnel stability problems were expected in both granite and diorite rock masses. The support system, suggested by empirical methods, was applied and the performance of suggested support system was evaluated by means of numerical modelling. It was concluded that the suggested support systems were adequate, since after applying the suggested support system to granite and diorite, tunnel deformation and the yielded elements around the tunnel decreased significantly. Thus, it is suggested that for more reliable support design empirical, numerical and analytical methods should be combined.  相似文献   

A Practical Procedure for the Measurement of Fragmentation by Blasting by Image Analysis   总被引：1，自引：0，他引：1  

J. A. Sanchidrián  P. Segarra  L. M. López 《Rock Mechanics and Rock Engineering》2006,39(4):359-382

Summary. The operation of a digital image analysis system in a limestone quarry is described. The calibration of the system, required in order to obtain moderately reliable fragmentation values, is done from muckpile sieving data by tuning the image analysis software settings so that the fragmentation curve obtained matches as close as possible the sieving. The sieving data have also been used to extend the fragment size distribution curves measured to sizes below the system’s optical resolution and to process the results in terms of fragmented rock, discounting the material coming from a loose overburden (natural fines) that is cast together with the fragmented rock. Automatic and manual operation modes of the image analysis are compared. The total fragmentation of a blast is obtained from the analysis of twenty photographs; a criterion for the elimination of outlier photographs has been adopted using a robust statistic. The limitations of the measurement system due to sampling, image processing and fines corrections are discussed and the errors estimated whenever possible. An analysis of consistency of the results based on the known amount of natural fines is made. Blasts with large differences in the amount of fines require a differentiated treatment, as the fine sizes tend to be the more underestimated in the image analysis as they become more abundant; this has been accomplished by means of a variable fines adjustment factor. Despite of the unavoidable errors and the large dispersion always associated with large-scale rock blasting data, the system is sensitive to relative changes in fragmentation.  相似文献   

On the origin of rock fragment mulches on Vertisols: A case study from the Ethiopian highlands   总被引：1，自引：2，他引：1  

Jan Moeyersons  Jan Nyssen  Jean Poesen  Jozef Deckers  Mitiku Haile 《Geomorphology》2006,76(3-4):411-429

Many Vertisols in Tigray, Ethiopia, typically carry a discontinuous rock fragment (RF, size 0.5–> 40 · 10^− 2 m) cover with 10 to 100 RFs m^− 2. Such RF mulches are of agricultural and environmental significance because they influence the water balance in the underlying soils and the crop yield. Natural RF concentrations are mostly considered as eolian or hydraulic lag deposits, or as the result of lateral transport over the soil surface from a rock outcrop, upslope. In cultivated areas RF mulches can develop by tillage.This paper presents the case of a natural RF mulch whose lithology indicates that the RFs are up-squeezed by the local Vertisol. The study site is located in the pass of Enda Maryam, Tigray, Northern Ethiopia (39°8′ E and 13°36′ N). A circular area of 10 m diameter, about 200 m away from the water divide in the valley has been cleared annually between 01/1999 and 05/2003. During this period, 625 RFs, 17 being > 7.5 · 10^− 2 m in size, totalling a mass of nearly 62 kg, have been collected. After correction for measurement procedures, the rate of RF up-warping by the Vertisol at Enda Maryam is assessed at 5 RFs m^− 2 in 3 years. At this rate of appearance, the formation of current RF concentrations on top of active valley Vertisols is only a matter of 10^1–2 years, provided the availability of RFs below the soil surface.Although important underground displacements were measured in the Vertisol between 01/1999 and 05/2002, the supposed link between up-squeezing of RFs and plastic deformations of ‘chimney’, ‘diapir’ or ‘intrusion’-like type in the Vertisol could not be evidenced. Instead, RFs are clearly concentrated on the soil surface as well as in depth, along the existing vertical desiccation cracks, often > 1 m deep which display polygonal configurations at the soil surface. Further, bundles of slickensides containing some RFs, have been mapped at the base of the Vertisol. The slickenside configuration suggests that the RF-bearing substrate is being scraped off.While the underground displacement of RFs along active slickensides seems normal, the process of RFs ascending in ‘upright’ position in the edge of desiccation cracks needs explanation. The closure of a desiccation crack is a peristaltic-like movement, following ascent or descent of the capillary fringe. It is hypothesized that this movement gradually pushes the RF to the surface or to another place or level in the soil profile where the crack closes in last instance.The apparent young age of the valley Vertisol mulches in Ethiopia might indicate the very recent formation of yearly recurrent desiccation cracks of Vertisols in the area. Available information confirms that most valleys in the study area used to be perennially marshy. Under these conditions no movements of RFs in the soil profile are expected to occur. Gullying, leading to pronounced seasonal desiccation of the Vertisols, started in several cases not more than 50 years ago.  相似文献   

Surface temperature differences between minerals in crystalline rocks: Implications for granular disaggregation of granites through thermal fatigue   总被引：4，自引：0，他引：4  

Miguel Gmez-Heras  Bernard J. Smith  Rafael Fort 《Geomorphology》2006,78(3-4):236-249

Thermal expansion differences between minerals within rocks under insolation have previously been assumed to drive breakdown by means of granular disaggregation. However, there have been no definitive demonstrations of the efficacy of this weathering mechanism. Different surface temperatures between minerals should magnify thermal expansion differences, and thus subject adjacent minerals to repeated stresses that might cause breakdown through fatigue failure. This work confirms the existence of surface temperature differences between minerals in granitic rocks under simulated short-term temperature fluctuations so as to discriminate their potential for initiating granular disaggregation. The influence of colour, as a surrogate for albedo, and crystal size, as a function of thermal mass are specifically identified because of their ease of quantification. Four rock types with a range of these properties were examined, and subjected to repeated short-term temperature cycles by radiative heating and cooling under laboratory conditions. Results show that while albedo is the main control for overall and individual maximum temperatures, crystal size is the main factor controlling higher temperature differences between minerals. Thus, stones with large differences of mineral sizes can undergo magnified stresses due to thermal expansion differences.  相似文献   

Processes and rates of rock fragment displacement on cliffs and scree slopes in an amba landscape, Ethiopia     

J. Nyssen  J. Poesen  J. Moeyersons  J. Deckers  Mitiku Haile 《Geomorphology》2006,81(3-4):265-275

Distinct rock fragment displacements occur on the ambas, or structurally determined stepped mountains of the Northern Ethiopian Highlands. This paper describes the rock fragment detachment from cliffs by rockfall, quantifies its annual rate, and identifies factors controlling rock fragment movement on the scree slopes. It further presents a conceptual model explaining rock fragment cover at the soil surface in these landscapes. In the May Zegzeg catchment (Dogu'a Tembien district, Tigray), rockfall from cliffs and rock fragment movement on debris slopes by runoff and livestock trampling were monitored over a 4-year period (1998–2001). Rockfall and rock fragment transport mainly induced by livestock trampling appear to be important geomorphic processes. Along a 1500-m long section of the Amba Aradam sandstone cliff, at least 80 t of rocks are detached yearly and fall over a mean vertical distance of 24 m resulting in a mean annual cliff retreat rate of 0.37 mm y^− 1. Yearly unit rock fragment transport rates on scree slopes ranged between 23.1 and 37.9 kg m^− 1 y^− 1. This process is virtually stopped when exclosures are established. Corresponding mean rock fragment transport coefficients K are 32–69 kg m^− 1 y^− 1 on rangeland but only 3.9 kg m^− 1 y^− 1 in densely vegetated exclosures. A conceptual model indicates that besides rockfall from cliffs and argillipedoturbation, all factors and processes of rock fragment redistribution in the study area are of anthropogenic origin.  相似文献   

云南三江口地区超基性岩岩石化学及成因   总被引：1，自引：0，他引：1  

俞赛赢  杨仕潘 《云南地质》2005,24(1):83-88

三江口地区超基性岩按岩石类型可分六种,岩石的m/f值小于6 5,属铁质超基性岩,呈包体状产于下二叠统木星土岩组(P1mx.)及上二叠统洛吉组(P2lj)中,与其为同源异相产物,形成于板块裂陷环境。岩浆活动时期大致为晚古生代 早三叠世早期,可能代表古特提斯形成的早期阶段。成果为进一步研究和恢复该区古构造格局提供重要依据。  相似文献   

金平龙脖河地区元古界龙脖河岩群的建立     

刘发刚  刘星  彭程  曾庆荣 《云南地质》2005,24(4):414-420

将金平县龙脖河口一带原划二叠纪的玄武岩组，三叠纪的个旧组、火把冲组，更正为元古代，并命名为龙脖河岩群。为研究该区的地层展布、大地构造环境、古地理、构造活动等提供了新资料。  相似文献   

Correlation of TBM and drilling machine performances with rock brittleness   总被引：9，自引：0，他引：9  

S. Kahraman   《Engineering Geology》2002,65(4):269-283

The correlations between three different methods of measuring brittleness and both drillability and borability were statistically investigated using the raw data obtained from the experimental works of different researchers.

Strong exponential relationships between the penetration rates of tunnel boring machine (TBM) and the brittleness of B₁ (the ratio of compressive strength to tensile strength) and B₂ (the ratio of compressive strength minus tensile strength to compressive strength plus tensile strength) were found. There is no correlation between the penetration rates of the diamond drilling tool and the brittleness values. Strong exponential correlations exist between the penetration rates of rotary drills and the brittleness of B₁ and B₂. However, no correlation between the penetration rate of rotary drills and the brittleness of B₃ (the product of percentage of fines in impact strength test and compressive strength) was found. The penetration rate of percussive drills does not exhibit a correlation with the brittleness of B₁ and B₂, but the penetration rate of percussive drills is strongly correlated with the brittleness of B₃.

It was concluded that each method of measuring brittleness has its usage in rock excavation depending on practical utility.  相似文献   

内蒙古宝音图岩群变质基性火山岩锆石U-Pb年龄及意义     

张玉清  苏宏伟 《华北地质》2002,(Z1)

内蒙古达茂旗宝音图岩群是在达茂旗、查干呼绍地区 1:5万区调和白云鄂博幅 1:2 5万区调过程中从过去的巴特敖包群和白云鄂博群未分岩组解体出来的中级变质岩系。通过对宝音图岩群中阳起钠长片岩、二云片岩 (原岩均为基性火山岩 )进行单颗粒锆石U -Pb法年龄测定 ,获得了两条不一致线上交点年龄 (2 486± 42 )Ma、(2 496± 2 6 )Ma ,代表了宝音图岩群基性火山岩及宝音图岩群的形成时代 ;在不一致线之外不同成因的锆石的2 0 7Pb/ 2 0 6Pb表面年龄 (2 2 2 7± 15 )Ma ,寓示着 2 2 0 0Ma左右发生了一次区域性变质热事件 ;下交点年龄 (319±486 )Ma和 (40 6± 46 )Ma ,代表了 2 5 0～ 480Ma时期该区大面积岩浆侵位及宝音图岩群后期变形变质改造的时期 ,两个年龄样的获得为研究古元古代古陆的裂解及白云鄂博海槽的形成提供了直接依据。  相似文献   

基于高温高压岩石破裂实验结果对中强地震前震中附近区域部分地震学现象的初步解释   总被引：6，自引：1，他引：6       下载免费PDF全文

蒋海昆  张流  周永胜  侯海峰  晁文海 《地震工程学报》2002,24(2):113-122

依据高温高压岩石破裂实验结果并结合理论分析，对 附近区域不同深度温压条件下岩石变形破坏性质及破坏失稳的力学行为进行了研究，在一次应力加载循环中，发生破坏的部位随时间具有向深部下迁的趋势。考虑到深度温压条件下岩石的渐进式破坏行为及突发失稳，对主震前震中附近区域小地震活动的增强、平静、活化等现象，以及b值等时间序列参数变化的可能机理进行初步探讨，并简单讨论了两类平静和两类b值变化的可能原因。  相似文献