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1.
After placement of cemented tailings backfill (CTB), which is a mixture of tailings (man‐made soil), water, and binder, into underground mined‐out voids (stopes), the hydration reaction of the binder converts the capillary water into chemically bound water, which results in the reduction of the water content in the pores of the CTB, thereby causing a reduction in the pore‐water pressure in the CTB (self‐desiccation). Self‐desiccation has a significant impact on the pore‐water pressure and effective stress development in CTB and paramount and practical importance for the stability assessment and design of CTB structures and barricades. However, self‐desiccation in CTB structures is complex because it is a function of the multiphysics or coupled (i.e., thermal, hydraulic, mechanical, and chemical) processes that occur in CTB. To understand the self‐desiccation behavior of CTB, an integrated multiphysics model of self‐desiccation is developed in this study, which fully considers the coupled thermal, hydraulic, mechanical, and chemical processes and the consolidation process in CTB. All model coefficients are determined in measurable parameters. Moreover, the predictive ability of the model is verified with extensive case studies. A series of engineering issues are examined with the validated model to investigate the self‐desiccation process in CTB structures with respect to the changes in the mixture recipe, backfilling, and the surrounding rock and curing conditions. The obtained results provide in‐depth insight into the self‐desiccation behavior of CTB structures. The developed multiphysics model is therefore a potential tool for assessing and predicting self‐desiccation in CTB structures. 相似文献
2.
土壤环境中化学定时炸弹的研究现状与展望 总被引：1，自引：0，他引：1
土壤环境中的化学定时炸弹对生态环境乃至人类自身危害极大,国内外均有大规模发生化学定时炸弹的实例,但是,由于其不易发现而常常被忽略,这将造成更为严重的后果。化学定时炸弹的分类问题比较复杂,目前较为妥当的做法是对各种分类方案进行有益的探索。化学定时炸弹的触爆机制研究十分重要,是进行地球化学灾害评价、预测和防治的基础;地球化学工程技术是将来预防和治理化学定时炸弹最主要手段。从科学的严密性和严肃性考虑,化学定时炸弹的概念应该由具有更深刻内涵和更广泛外延的“缓变型地球化学灾害”来替代。 相似文献
3.
为探究不同充填间隔时间(FTS)和料浆浓度对胶结充填体长期强度影响机制,配制70%、72%、75%三个浓度、充填间隔时间为12、24、36、48 h的两分层胶结充填体试件,开展单轴抗压强度(UCS)试验并探究其力学特性及其破坏形式。试验结果表明,（1）胶结充填体峰值抗压强度随充填间隔时间增大而呈递减趋势,充填间隔时间一定时胶结充填体抗压强度随料浆浓度增大而增大,且峰值抗压强度与充填间隔时间呈多项式函数规律;（2）胶结充填体试件加载过程中表现为压密阶段、线弹性阶段、裂纹扩展阶段和破坏发展4个阶段,随充填间隔时间延长,胶结充填体的破坏形式可能表现为张拉破坏–拉剪破坏过渡–拉剪混合破坏的损伤模式。研究结论能够为后期充填体强度设计和稳定性控制提供有益参考。 相似文献
4.
The disturbed state concept (DSC) model, and a new and simplified procedure for unloading and reloading behavior are implemented in a nonlinear finite element procedure for dynamic analysis for coupled response of saturated porous materials. The DSC model is used to characterize the cyclic behavior of saturated clays and clay–steel interfaces. In the DSC, the relative intact (RI) behavior is characterized by using the hierarchical single surface (HISS) plasticity model; and the fully adjusted (FA) behavior is modeled by using the critical state concept. The DSC model is validated with respect to laboratory triaxial tests for clay and shear tests for clay‐steel interfaces. The computer procedure is used to predict field behavior of an instrumented pile subjected to cyclic loading. The predictions provide very good correlation with the field data. They also yield improved results compared to those from a HISS model with anisotropic hardening, partly because the DSC model allows for degradation or softening and interface response. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
5.
Observations of the solar butterfly diagram from sunspot records suggest persistent fluctuations in parity, away from the overall, approximately dipolar pattern. A simple mean-field dynamo model is used with a solar-like rotation law and perturbed α effect. The parity of the magnetic field relative to the rotational equator can demonstrate can be described as resonance behavior, while the magnetic energy behaves in a more or less expected way. Possible applications of this effect are discussed in the context of various deviations of the solar magnetic field from dipolar symmetry, as reported from analyses of archival sunspot data. The model produces fluctuations in field parity, and hence in the butterfly diagram, that are consistent with observed fluctuaions in solar behavior. 相似文献
6.
T. G. Sitnik 《Astronomy Reports》2010,54(4):317-326
Using the results of our Hα interferometric observations and observational data on the 21 cm and CO lines, we have analyzed the structure and kinematics
of the interstellar medium in the extended vicinity of the star WR 137 and the supernova remnants CTB 87 and G73.9+0.9. A
shell structure with a radius of up to 40′ observable in optical lines has been discovered around WR 137. The high-velocity
motions of ionized hydrogen inside this shell can be interpreted as expansion of the gas swept out by the wind of WR 137 at
velocities of up to 60 km/s. The ionized hydrogen near WR 137 emits at the systematic velocity V
LSR ∼ 6–18 km/s. The expansion ofG73.9+0.9 at a velocity of up to 55 km/s has been confirmed. The systematic velocities of the
ionized hydrogen toward this supernova remnant are V
LSR ≃ −14…+14 km/s. An HI shell around G73.9+0.9 has been detected at velocities V
LSR≃−14…−8 km/s. A very faint optical shell of CTB 87 with a size of about 20′ has also been detected. Evidence that CTB 87 is
located in the Cygnus Arm is presented. 相似文献
7.
D. V. Klepikov B. P. Filippov A. Ajabshirizadeh Yu. V. Platov 《Astronomy Reports》2006,50(10):834-841
The behavior of magnetic foci—intersection points of tangents to ray structures in the polar corona of the Sun—is studied. This behavior reflects the evolution of the large-scale magnetic field near the poles, and is one of only a few sources of information on the polar magnetic field of the Sun. For the first time, the positions of the magnetic foci are plotted as a function of the solar-cycle phase for a full cycle, based not only on total-eclipse images but also on daily coronal observations in the FeIX and FeX (171 Å) lines carried out with the EIT telescope on the SOHO satellite. The temporal behavior of the foci over a cycle differs appreciably from that inferred from isolated observations during eclipses. The curve agrees fairly well with the model of the global-field evolution suggested by us previously. 相似文献
8.
An infinite element is presented to treat wave propagation problems in unbounded saturated porous media. The porous media is modeled by Biot's theory. Conventional finite elements are used to model the near field, whereas infinite elements are used to represent the behavior of the far field. They are constructed in such a way that the Sommerfeld radiation condition is fulfilled, i.e. the waves decay with distance and are not reflected at infinity. To provide the wave information the infinite elements are formulated in Laplace domain. The time domain solution is obtained by using the convolution quadrature method as the inverse Laplace transformation. The temporal behavior of the near field is calculated using standard time integration schemes, e.g. the Newmark method. Finally, the near and far field are combined using a substructure technique for any time step. The accuracy as well as the necessity of the proposed infinite elements, when unbounded domains are considered, is demonstrated by different examples. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
9.
Micropiles are being increasingly utilized in foundation rehabilitation and seismic retrofitting projects. The function of
the micropiles in these projects is to enhance the foundation ultimate capacity as well as reduce foundation deflection. This
paper focuses on an analytical model for micropile load-displacement behavior subjected to compressive as well as tensile
loading. The soil-micropile interaction is considered explicitly in the model development. Furthermore, to keep the model
simple and accessible to designers, the micropile-soil interface is assumed to be linearly elastic-perfectly plastic and homogeneous
with depth. Closed form expressions of micropile deformation as a function of applied load are presented. These expressions
are used to study the effect of model parameters on micropile yield behavior. Micropile strain distribution and the load transfer
behavior calculated by the model are discussed. The model calculations are compared with the field measured load-displacement
curves. The measured micropile load-displacement data available in the literature are analyzed to evaluate the model parameters.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
Constitutive model with time-dependent deformations 总被引：4，自引：0，他引：4
Anette Krogsbll 《Engineering Geology》1998,49(3-4):285-292
In many geological and engineering problems it is necessary to transform information from one scale to another. Data collected at laboratory scale are often used to evaluate field problems on a much larger scale. This is certainly true for geological problems where extreme scale differences are common in time as well as size. This problem is addressed by means of a new constitutive model for soils. It is able to describe the behavior of soils at different deformation rates. The model defines time-dependent and stress-related deformations separately. They are related to each other and they occur simultaneously. The model is based on concepts from elasticity and viscoplasticity theories. In addition to Hooke's law for the elastic behavior, the framework for the viscoplastic behavior consists, in the general case (two-dimensional or three-dimensional), of a yield surface, an associated flow rule and a hardening law. The model is formulated in incremental terms and is therefore suitable for computational modeling and it has been implemented in a computer program used for analyzing the depositional history of an oil field in the Danish part of the North Sea. An important part of the problem in this case was the difference in time scale between the geological process of deposition (millions of years) and the laboratory measurements of mechanical properties (minutes or hours). In addition, the time scale relevant to the production history of the oil field was interesting (days or years). 相似文献
11.
考虑桩-土体系渐进破坏的单桩承载特性研究 总被引：1，自引：0，他引：1
针对目前桩基承载特性确定时未考虑桩-土体系渐进变形过程的现状,采用现场试验和理论分析等手段对考虑桩-土体系渐进破坏的单桩承载特性展开研究。首先,利用现场试验数据对侧阻和端阻的软化特性展开深入探讨,提出了侧阻和端阻软化模型,明确了模型中各参数取值方法,并验证了其合理性。同时,根据提出的侧阻和端阻软化模型,建立了一种可考虑桩-土体系渐进破坏的单桩承载特性的迭代算法。算例分析表明,计算获得的破坏性单桩承载特性与实测值有较好的一致性,且可反映侧阻和端阻的破坏特性。实际工程中,结合单桩承载特性分析算法,可根据单桩的实际受力特点灵活选用不同形式的侧阻和端阻荷载传递函数来分析不同桩顶荷载水平下的单桩受力特性。 相似文献
12.
二滩高拱坝坝基渗流场的反演分析 总被引：2，自引：0，他引：2
研究运行期高坝坝基渗流特性时,渗流场参数的获取是难点之一。针对二滩工程,利用三维渗流场有限元精细求解技术以及遗传算法等方法和理论,建立坝基渗流场反演模型;选择坝基典型渗压计测点作为实测点,通过特定时刻库水位对应渗流场的反演获得坝基渗透系数,再利用不同时刻点库水位对应的渗流场进行验证。分析结果表明,渗流场的反演结果是合理的,可作为研究运行期高拱坝坝基渗流场真实工作性态的依据。 相似文献
13.
《地学前缘(英文版)》2016,7(1)
Hydrocarbon production from shale has attracted much attention in the recent years. When applied to this prolific and hydrocarbon rich resource plays, our understanding of the complexities of the flow mechanism(sorption process and flow behavior in complex fracture systems- induced or natural) leaves much to be desired. In this paper, we present and discuss a novel approach to modeling, history matching of hydrocarbon production from a Marcellus shale asset in southwestern Pennsylvania using advanced data mining, pattern recognition and machine learning technologies. In this new approach instead of imposing our understanding of the flow mechanism, the impact of multi-stage hydraulic fractures, and the production process on the reservoir model, we allow the production history, well log, completion and hydraulic fracturing data to guide our model and determine its behavior. The uniqueness of this technology is that it incorporates the so-called "hard data" directly into the reservoir model, so that the model can be used to optimize the hydraulic fracture process. The "hard data" refers to field measurements during the hydraulic fracturing process such as fluid and proppant type and amount, injection pressure and rate as well as proppant concentration. This novel approach contrasts with the current industry focus on the use of "soft data"(non-measured, interpretive data such as frac length, width,height and conductivity) in the reservoir models. The study focuses on a Marcellus shale asset that includes 135 wells with multiple pads, different landing targets, well length and reservoir properties. The full field history matching process was successfully completed using this data driven approach thus capturing the production behavior with acceptable accuracy for individual wells and for the entire asset. 相似文献
14.
The potential consequences of bedload transport of postlarvae for patterns of distribution of marine invertebrates were explored
by developing a bedload transport model for juvenile bivalves in a small estuary in New Jersey, USA. A simple numerical model
of tidal current hydrodynamics was developed based on field measurements of shear stresses near the bottom. Burrowing behavior
of bivalves was incorporated into the model of bedload transport by using estimates of entrainment rates of Gemma gemma and Mya arenaria in a laboratory flume, and jump lengths of the bivalves were estimated by methods previously developed for noncohesive particles.
Based on the flood domination and strong gradient of shear stresses in the Navesink estuary, our model predicted that juvenile
bivalves would accumulate in the center of the estuary, traveling up to several kilometers over 30 days. Field distributions
of juvenile bivalves were consistent with the model predictions for other species of bivalves but not for G. gemma, for which field distributions of both <500- and >500-μm individuals were concentrated in the eastern end of the estuary.
Differences between the bedload model and G. gemma distributions suggest that spatial variation in burrowing behavior or biological interactions are playing an important role
in maintaining distribution patterns of this species in spite of high levels of bedload transport. This modeling approach
is applicable to other juvenile benthic invertebrates that disperse as bedload and is a useful model against which to compare
field observations of rates of transport and patterns of distribution and abundance. 相似文献
15.
Stress–strain modeling of sand–silt mixtures is important in the analysis and design of earth structures. In this paper, we develop a stress–strain model that can predict the behavior of sand–silt mixtures with any amount of fines content. This model is based on a micromechanics approach, which involves mean‐field assumptions. For the mixtures with low amount of fines, the mechanical behavior is dominated by sand grains network. On the other hand, for the mixtures with high amount of fines, the mechanical behavior is dominated by silt grains network. Using this concept of dominant grains network, the behavior of mixtures with any amount of fines can be predicted from knowing the behavior of sand and silt, alone. We also modeled the critical state friction angle, critical state void ratio, and elastic stiffness for the mixtures as a function of fines content. The applicability of this developed stress–strain model is shown by comparing the simulated and measured results for two different types of sand–silt mixtures with full range of fines content. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
16.
松软破碎岩体的复杂力学特性给深部开采工程带来一系列棘手的问题,深入研究破碎岩体峰后力学行为,对于深部巷道围岩稳定性分析及支护结构设计具有重要意义。基于量化GSI围岩评级系统及连续介质理论,建立了考虑围压影响的破碎岩体峰后应变软化力学模型。通过工程应用实例验证了数值模型的可靠性。研究结果表明：通过计算围岩与支护结构相互作用关系可知,理想弹塑性模型和应变软化模型所得计算结果差异较大,采用理想弹塑性模型进行支护设计,可能导致支护结构的安全性偏低,甚至失稳。现场应用结果表明：数值计算结果与现场实际情况吻合;提出的深部破碎岩体应变软化模型能够较为真实地反映破碎岩体的非线性破坏行为,可为硐室围岩稳定性分析及支护结构设计等提供新的思路。 相似文献
17.
INTRODUCTIONUnderstanding dynamic response andits correla-tion to the effects of traffic , wind and earthquake hasbecome one of the engineering challenges of cable-stayed bridges , since the cable-stayed bridges arepresently extending to medium- and long-spanlengths .Investigations of both the aerodynamic sta-bility and earthquake response of cable-stayed bridgesare dependent upon knowledge of the dynamic char-acteristics ,such as natural frequencies , mode shapesand modal damping values ,… 相似文献
18.
Some Evidence for a Possible Extraterrestrial Event at／near Permian—Triassic Boundary 总被引：1，自引：0，他引：1
XuDaoyi 《中国地质大学学报(英文版)》2002,13(2):151-156
A selection of evidence, including a carbon isotopic excursion, iridium anomaly, fullerenes (C60 and C70) with trapped noble gasses, microspherules and shocked quartz, is discussed in this paper. All the evidence in hand favors the hypothesis that the PTB event was probably related to an extraterrestrial cause, and the impact would lead to great physical change, including large volcanic eruptions. on the earths surface. The ET markers for the CTB event could be considered only as an example, and cannot be taken as a unique standard of an ET event. 相似文献
19.
A kinematic hardening based model for unsaturated soils considering different hydraulic conditions 
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下载免费PDF全文 At present, several of the existing elastoplastic constitutive models are adapted for describing the stress–strain behavior of unsaturated soils. However, most of them present certain limitations in this field. These limitations can be related to the basic model and/or added unsaturated state variables and formulations. In this regard, inability to model the hydro‐mechanical behavior in constant water (CW) conditions is an example of these limitations. In this paper, an advanced version of CJS model is selected for adaptation to the unsaturated states. Adaptation to unsaturated states is achieved in the framework of effective stress approach. Effective stress equation and unsaturated state variables are selected based on the recent research existing in the literature. The developed model is capable of describing the complex behavior of unsaturated soil in the CW condition in addition to predicting the behavior at failure and post–failure, nonlinear elastoplastic behavior at low levels of stress and strain (by selecting a very small elastic domain), as well as wetting and collapse behaviors. In order to validate the model, results of triaxial tests in CD and CW conditions are used. The validation results indicate the good capability of the proposed model. Behavior of the unsaturated soils during wetting is an important issue. For this reason, the model is also evaluated based on the results of wetting and collapse triaxial tests. A comparison between the tests and simulation results shows that the model is able to predict the soil behavior under the wetting path. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
20.
Numerical simulations of flow motion and deposition characteristics of granular debris flows 总被引：2，自引：1，他引：1
Flow motion and deposition characteristics of debris flows are of concern regarding land use planning and management. A simple
model for the prediction of mentioned characteristics has been developed, incorporating a friction–collision rheological model.
It demonstrated to be able to satisfactorily simulate the two-dimensional behavior of laboratory results and the one-dimensional
behavior of two real debris-flow events. The numerical results show that the topography of the channel bed, the yield stress
level of the debris flows, and the inflow pattern have significant influence on the simulated flow motion and deposition characteristics
of debris flows. In addition, the predicted run-out distance has been compared with analytical solutions and field observations.
The model could be employed for the preliminary evaluation of one-dimensional run-out distance of granular debris flows provided
that the volume of the debris involved in the initial mobilization is assumed. 相似文献