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1.
表征单元体(REV) 的存在是应用连续介质力学方法对岩体进行研究的前提,REV可以从岩体块体化程度的角度进行研究,裂隙大小及其统计分布是影响岩体块体化程度REV的重要因素。本文利用课题组自主研发的GeneralBlock 软件,建立更一般化实际化的模型,研究裂隙延展性统计分布的离散程度对岩体块体化程度REV的影响。分析时选取了最常用的裂隙延展性统计分布形式:正态分布。由于所建立的岩体结构模型是随机的,需要对每个随机裂隙模型进行多次实现。为节省计算量,当研究范围比较小时,对每种结构的每个研究范围进行9次随机实现。当研究范围足够大,达到REV大小的时候进行100次随机实现。为确定离散程度对表征单元体的影响,本文针对5个不同标准差进行了模拟分析（共建立了1 005个裂隙模型,分别进行了块体识别并计算其块体化程度B）。结果表明,裂隙延展性服从正态分布的情况下,如果其平均值一定,岩体的块体化程度随着统计分布离散程度的增加略有上升,裂隙岩体的REV值基本上由裂隙延展性统计平均值决定。 相似文献
2.
The Development of a new Numerical Modelling Approach for Naturally Fractured Rock Masses 总被引：1，自引：3，他引：1
Summary. An approach for modelling fractured rock masses has been developed which has two main objectives: to maximise the quality
of representation of the geometry of existing rock jointing and to use this within a loading model which takes full account
of this style of jointing. Initially the work has been applied to the modelling of mine pillars and data from the Middleton
Mine in the UK has been used as a case example. However, the general approach is applicable to all aspects of rock mass behaviour
including the stress conditions found in hangingwalls, tunnels, block caving, and slopes. The rock mass fracture representation
was based on a combination of explicit mapping of rock faces and the synthesis of this data into a three-dimensional model,
based on the use of the FracMan computer model suite. Two-dimensional cross sections from this model were imported into the
finite element computer model, ELFEN, for loading simulation.
The ELFEN constitutive model for fracture simulation includes the Rotating Crack, and Rankine material models, in which fracturing
is controlled by tensile strength and fracture energy parameters. For tension/compression stress states, the model is complemented
with a capped Mohr-Coulomb criterion in which the softening response is coupled to the tensile model. Fracturing due to dilation
is accommodated by introducing an explicit coupling between the inelastic strain accrued by the Mohr-Coulomb yield surface
and the anisotropic degradation of the mutually orthogonal tensile yield surfaces of the rotating crack model. Pillars have
been simulated with widths of 2.8, 7 and 14 m and a height of 7 m (the Middleton Mine pillars are typically 14 m wide and
7 m high). The evolution of the pillar failure under progressive loading through fracture extension and creation of new fractures
is presented, and pillar capacities and stiffnesses are compared with empirical models. The agreement between the models is
promising and the new model provides useful insights into the influence of pre-existing fractures. Further work is needed
to consider the effects of three-dimensional loading and other boundary condition problems. 相似文献
3.
Francisco H.R. Bezerra Vanildo P. da Fonseca Claudio Vita-Finzi Francisco P. Lima-Filho Allaoua Saadi 《Engineering Geology》2005,76(3-4):191-208
We have identified numerous well-preserved elutriation and fluidization structures probably induced by liquefaction in Quaternary gravels and gravelly sediments of braided fluvial channel deposits in the Rio Grande do Norte and Ceará states, northeastern Brazil. They show evidence of upward-directed water escape after sediment deposition and before sediment compaction. Among the several types of structures observed, the most frequent are pillars, pockets and dikes. These structures range in width from a few centimeters to as much as 4 m, and in height from 60 cm to 4 m. Dikes, pillars and pockets are systematically associated. Clastic dikes vented large quantities of sand to the upper layers or the surface; pebbles and cobbles from the host rock sank into the dikes and formed pillars and pockets. Pockets form the root part; pillars form the intermediate part and dike, the upper part of the composite structure. The morphology of the structures in sectional and plan views indicates a 3D geometry composed of a tabular dike and pillar that present a downward continuous transition to a bowl-shaped pocket. This “stratigraphy” of liquefaction features is different from that usually presented in the current literature.
Field data suggest that both the location and the geometry of the features were controlled by sedimentary properties rather than joints and small faults. The size and abundance of these features suggest that they were formed by great events rather than localized mechanisms. Field evidence also indicates that these features are the product of fluidization and elutriation and may have been induced by liquefaction processes associated with seismic shaking. A nonseismic origin related to elutriation processes, however, cannot be ruled out for some of the features. 相似文献
4.
Palaeo-karst collapse pillars in northern China and their damage to the geological environments 总被引：4，自引：0，他引：4
According to statistics, there are a total of 39 sites of palaeo-karst collapse pillars in Northern China, as well as 3,650
palaeo-karst collapse pillars. Through an overall survey and analysis of the distribution regularities and formation mechanisms
of palaeo-karst collapse pillars in the northern coal mine regions, this paper found that the rock formation structures, geological
structures, karst characters, underground hydrodynamic conditions of karst and neotectonic movement conditions are basic geological
bases for the formation of karst collapse pillars and rule the distribution of them. Karst collapse pillars apparently have
three south–north regularities in terms of distribution, and they have resulted in severe damages to geological resources
and environment in their distribution areas: mine water inrush causing and coal resources damage and influencing the impounding
of reservoirs as well as the stability of dam sites. Based on the basic geological features of palaeo-karst collapse pillars
in northern China, this paper also introduces the new methods of integrated prospecting of successive approximation to determine
hydraulic conductivity of palaeo-karst collapse pillars. 相似文献
5.
G. G. Boeskorov P. R. Nogovitsyn E. N. Mashchenko I. N. Belolyubsky A. D. Stepanov V. V. Plotnikov A. V. Protopopov M. V. Shchelchkova J. van der Plicht N. G. Solomonov 《Doklady Earth Sciences》2016,469(1):647-651
This paper considers the data on new findings of mammoth fauna remains in the Middle Lena basin used to specify the species composition of large Late Neopleistocene mammals represented by eleven species. The obtained range of radiocarbon dates made it possible to state that mass burials of Pleistocene mammal remains were formed in the region during the Karginsk Interstadial (24 000–55 000 years ago). 相似文献
6.
Cao Zhimin Luo Yaonan Li Youguo Song Xieyan Chen Cuihua Yang Zhusheng He Hong WT ”BX 《地学前缘》2000,(Z1)
Cu-Ni-PGES MINERALIZATION OF MELANOCRATIC ROCKS IN SOUTHEAST MARGIN OF THE QINGHAI-XIZANG(TIBET) PLATEAU, HKTERALIZAtheprojectsupportedbyNNSFofChina 相似文献
7.
用三维梁-颗粒模型BPM3D(beam-particlemodelinthreedimensions)对岩石类非均质脆性材料的力学性质和破坏过程进行了数值模拟。梁-颗粒模型是在离散单元法基础上,结合有限单元法中的网格模型提出的用于模拟岩石类材料损伤破坏过程的数值模型。在模型中,材料在细观层次上被离散为颗粒单元集合体,相邻颗粒单元由有限单元法中的弹脆性梁单元联结。梁单元的力学性质均按韦伯(Weibull)分布随机赋值,以模拟岩石类材料力学参数的空间变异性。材料内部裂纹通过断开梁单元来模拟。通过自动生成的非均质材料模型对岩石类材料的破坏机理进行研究。岩石类非均质脆性材料在单轴压缩状态下破坏过程细观数值模拟结果显示,岩石材料宏观破坏是由于其内部细观裂纹产生、扩展、贯通的结果。通过数值模拟结果之间的对比分析,揭示出岩石试样宏观破坏模式随细观层次上韦伯分布参数的变化而不同。与实际矿柱破坏形态的对比分析表明了模型的适用性。根据数值模拟结果对岩石类非均质材料的破坏机理进行了探讨。 相似文献
8.
V. I. Vinogradov G. A. Belenitskaya B. G. Pokrovsky M. I. Bujakaite 《Lithology and Mineral Resources》2011,46(1):71-84
Isotopic compositions of carbon and oxygen in carbonates and sulfur in sulfates of the Verkhnyaya Lena Formation (ε2–ε3), which terminates the Cambrian section of the Irkutsk Amphitheater of the Siberian Craton, are studied. Sulfates of the Verkhnyaya Lena Formation are marked by unusually low δ34S values (4.6–12.0‰) relative to sulfates of the underlying Angara Formation. This is likely caused by variations in the facies-paleogeographic sedimentation at the transition of the Angara and Verkhnyaya Lena formations, as well as associated variations in the water and salt alimentation budget in sedimentation basins, due to their isolation from open sea and intensification of the continental and underground discharge. The δ18O(PDB) value in carbonates decreases from ?4.4‰ at bottom to ?10.4‰ at top, reflecting variation in postsedimentary transformations and probable continuous freshening of sedimentation basin. Isotopic composition of carbon in most samples shows normal marine δ13C values (0 ± 1‰). Only in some samples, does the δ13C value increase up to ?3.8 and 2.2‰ due to specific features of postsedimentary processes. The Rb-Sr systems of the clayey component of marls from the 500-m-thick section of the Angara Formation and bottom of the Verkhnyaya Lena Formation record an age of 512 ± 10 Ma, which is close to the assumed stratigraphic age of the Verkhnyaya Lena Formation. The 87Sr/86Sr initial ratio is 0.7082 ± 0.0004. 相似文献
9.
This study was based on the discrete fracture model to investigate the influence of fracture parameters on the solute transport
in the fractured rocks of andesite in Lan-Yu island, Taiwan. In the simulation cases, the centers of fractures, fracture lengths
and apertures were assumed to have Poisson’s distribution, negative exponential distribution and lognormal distribution, respectively.
With the above assumptions, constructing the discrete fracture model became practicable. Using the mass-balance equation with
specified boundary conditions, the flow field in the rock was solved. Then particles were released under the flow field. Monte
Carlo method was used assuming that the amount of particles was proportional to the flow rates to get the particle accumulated
percentage breakthrough curve and to estimate the dispersion coefficient. On the basis of the discrete fracture model, it
was possible to evaluate the property of dispersion behavior of andesite in Lan-Yu Island with flow and transport mechanism.
Properties of the dispersion behavior such as the relation between distance and traveling-time (ln〈r
2〉 and ln 〈t〉), anisotropic behavior, and the overall dispersion coefficient in a fracture network were characterized: the slope value
of ln〈r
2〉 and ln〈t〉 was 1.64 an indication of non-Fickian dispersion, the particles dispersion along the flow (D11) was bigger than that perpendicular
to the flow (D22), and the dispersion coefficient by this study was 0.91 m comparing the value 1 m from Sauty’s method. 相似文献
10.
E. Karimzade M. Sharifzadeh H. R. Zarei K. Shahriar M. Cheraghi Seifabad 《Arabian Journal of Geosciences》2017,10(9):206
Groundwater flow is a major issue in underground opening in fractured rocks. Because of finding the fracture connectivity, contribution of each fracture in flow, and fracture connectivity to excavation boundary, the prediction of water flow to underground excavations is difficult. Simulation of fracture characteristics and spatial distribution is necessary to obtain realistic estimation of inflow quantity to tunnel and underground excavations. In this research, a computer code for three-dimensional discrete fracture network modeling of water inflow into underground excavations was developed. In this code, the fractures are simulated as ellipsoid while geometrical properties of the fractures are reproduced using a stochastic method. Properties such as the size, orientation, and density of the fractures are modeled by their respective probability distributions, which are obtained from field measurements. According to the fracture condition, the flow paths in rock mass are determined. The flow paths are considered as channels with rectangular sections in which channel width and fracture aperture determine geometry of channel section. Inflow into excavation is predicted ignoring matrix permeability and considering the hydrogeological conditions. To verify presented model, simulation results were compared to a part of the Cheshmeh-Roozieh water transfer tunnel in Iran. The results obtained from this research are in good agreement with the field data. Thus, the average of the predicted inflow has just an approximation error equal to 17.8%, and its standard deviation is 8.6 l/s, which is equal to 21% of the observed value that demonstrates low dispersion of the predicted values. 相似文献
11.
云南东川蒋家沟泥石流形成内因初探 总被引：6，自引：2，他引：4
泥石流形成的因素众多,不仅与地形地貌、降雨特征、地震、人类活动等外部因素有关,还与泥石流岩土体自身的黏土矿物成分、颗粒级配、化学成分、土体分散性、地下水环境等内部因素密切相关。在室内对蒋家沟泥石流源区土体进行黏土矿物分析、颗粒分析、化学成分定量分析、分散度和ESP值测试、地下水分析,初步探讨了蒋家沟泥石流形成的内在原因,得到：蒋家沟泥石流体的黏土矿物成分以伊利石为主,占30 %,其化学成分也与伊利石接近;ESP值、分散度平均值分别达到24.6 %、59.1 %,属于高分散性土,且土壤贫瘠;地下水矿化度高,硬度大,破坏了岩土体自身的结构和稳定性,形成大量松散物质,为泥石流的形成提供丰富的物源。 相似文献
12.
The internal structure of placer gold depends on its residence time under exogenetic conditions. Two types of placer gold
are distinguished in the middle Lena River basin by typomorphic features. Gold of distal transfer (type I) is characterized
by recrystallized structure, deformation lines, and thick high-fineness rims indicating long-term residence under exogenetic
conditions; and multifold redeposition in transitional reservoir rocks. Gold of proximal transfer (type II) is characterized
by a vague zonal structure, thin or discontinuous high-fineness rims, granulation, and disintegration structures indicating
short-term residence time under the exogenetic conditions. Gold of proximal transfer is spatially confined to the zones of
ancient long-living faults. Thus, it is possible to suggest that this type of gold might have derived from local Middle Paleozoic
or Mesozoic gold sources. 相似文献
13.
V. B. Spektor V. V. Spektor N. T. Bakulina N. V. Torgovkin A. M. Cherepanova G. T. Maksimov L. G. Neradovskii 《Doklady Earth Sciences》2016,467(1):232-235
An inlier of Jurassic rocks is identified for the first time at the surface of the first terrace above a floodplain composed of Holocene sediments on the left side of the Lena River. It represents a block of Jurassic rocks similar compositionally to rocks in outcrops on the left slope of the river valley. It is shown that the block was displaced along faults in the Holocene. The rocks of the inlier are deformed, and the Paleogene–Neogene sequence covering the plateau (altitude approximately 200 m) is displaced in the stepwise mode to the level corresponding to the bottom of the Lena River valley (altitude approximately 100 m). The Holocene alluvium enveloping the inlier belongs to the constratal type being up to 40 m thick. Steep faceted morphostructures on the left slope of the Lena River valley coincide with the faults. The left slope of the valley is crossed exclusively by young incisions. It is assumed that Holocene movements may be reactivated in the future. 相似文献
14.
N. Kosheleva E. Karabanov A. Kositskiy D. Williams S. Armstrong 《Journal of Geochemical Exploration》2006,88(1-3):118
A channel account approach is proposed to estimate longitudinal changes in runoff along large river systems. This new method provides a quantitative basis for describing the fluvial transport of suspended particulate material and dissolved substances. This method includes an evaluation of basic elements of water balance in separate sections of the river network and subsequent correction of channel accounting equations for the entire system using a maximum likelihood principle. To calculate water discharges of tributaries that have no hydrological information, structural analysis of river network is performed. This approach provides less error in comparison with traditional methods of estimating lateral inflow. The method is used to trace water discharge with increasing distance along the Lena river basin and to evaluate the contribution of geologically and lithologically uneven sub-basins in water discharge formation during a summer low water period. 相似文献
15.
Naturally fractured mine pillars provide an excellent example of the importance of accurately determining rock mass strength.
Failure in slender pillars is predominantly controlled by naturally occurring discontinuities, their influence diminishing
with increasing pillar width, with wider pillars failing through a combination of brittle and shearing processes. To accurately
simulate this behaviour by numerical modelling, the current analysis incorporates a more realistic representation of the mechanical
behaviour of discrete fracture systems. This involves realistic simulation and representation of fracture networks, either
as individual entities or as a collective system of fracture sets, or a combination of both. By using an integrated finite
element/discrete element–discrete fracture network approach it is possible to study the failure of rock masses in tension
and compression, along both existing pre-existing fractures and through intact rock bridges, and incorporating complex kinematic
mechanisms. The proposed modelling approach fully captures the anisotropic and inhomogeneous effects of natural jointing and
is considered to be more realistic than methods relying solely on continuum or discontinuum representation. The paper concludes
with a discussion on the development of synthetic rock mass properties, with the intention of providing a more robust link
between rock mass strength and rock mass classification systems. 相似文献
16.
Georg Schwamborn Lutz Schirrmeister Ali Mohammadi Hanno Meyer Andrei Kartoziia Flavio Maggioni Jens Strauss 《Sedimentology》2023,70(1):235-258
Arctic warming and permafrost thaw visibly expose changes in the landscape of the Lena River delta, the largest Arctic delta. Determining the past and modern river regime of thick deltaic deposits shaping the Lena River mouth in north-eastern Siberia is critical for understanding the history of delta formation and carbon sequestration. Using a 65 m long sediment core from the delta apex a set of sedimentological techniques is applied to aid in reconstructing the Lena River history. The analysis includes: (i) grain-size measurements and the determination of the bedload composition; (ii) X-ray fluorescence, X-ray diffractometry, and magnetic susceptibility measurements and heavy mineral analysis for tracking mineral change; (iii) pH, electrical conductivity, ionic concentrations, and the δ18O and δD stable isotope composition from ground ice for reconstructing permafrost formation. In addition; (iv) total and dissolved organic carbon is assessed. Chronology is based on; (vi) radiocarbon dating of organic material (accelerator mass spectrometry and conventional) and is complemented by two infrared – optically stimulated luminescence dates. The record stretches back approximately to Marine Isotope Stage 7. It holds periods from traction, over saltation, to suspension load sedimentation. Minerogenic signals do not indicate provenance change over time. They rather reflect the change from high energy to a lower energy regime after Last Glacial Maximum time parallel to the fining-up grain-size trend. A prominent minimum in the ground ice stable isotope record at early Holocene highlights that a river arm migration and an associated refreeze of the underlying river talik has altered the isotopic composition at that time. Fluvial re-routing might be explained by internal dynamics in the Lena River lowland or due to a tectonic movement, since the study area is placed in a zone of seismic activity. At the southern Laptev Sea margin, onshore continental compressional patterns are bordering offshore extensional normal faults. 相似文献
17.
Martin KNEZ Tadej SLABE 《《地质学报》英文版》2007,81(1):148-157
Shilin is among the most interesting form of stone forest to occur in karst landscapes. They develop from karren subsoil, and their shapes, entire forests or just individual pillars and their rock relief, depend on the conditions under which they were formed, their location in the karst landscape, and above all on the characteristics of the rock： its composition, stratification, and fissuring. Because of the exceptional characteristics of this karst phenomenon in China, we propose that the term ＂shilin＂ be used in the professional literature for this type of stone forest. 相似文献
18.
龙游石窟1号洞和其他4个洞体,开发16a来,在取得了丰硕的社会经济效益和学术成果的同时,洞体在自然力的作用下,出现了严重的破坏。构成石窟的柱、墙和顶板陆续出现裂缝。其原因是构成洞体的泥质砂岩易于风化、易于流变,在干湿交替和温度变化的情况下极易破坏。同时处于浅埋状态的洞室顶板、柱子、墙体强度不足,在自重作用下发生以冲切、剪切、弯曲为主要特征的破坏形式。开发时施加的外部荷载加剧了这种破坏。针对这些破坏形式,加固方案宜采用整体设计分步实施的方案。先柱墙,后顶板。柱墙加固以柱支撑为主要手段,顶板以梁支撑为主要手段。两者相互联系形成一个美观的加固体系。 相似文献
19.
Triassic sections of the Lena lower reaches (northern Yakutia) were studied. Stratigraphy and paleontology of the Triassic deposits were refined and described in detail, and their age was constrained by different fauna groups. The first detailed local Triassic biostratigraphic scheme is reported, which includes ammonoid, nautiloid, and bivalve zones and subzones and foraminifer beds. The scheme is compared with the Canadian Triassic Zonal and Standard (International) Scales. 相似文献