围压与轴压共同作用对恐龙化石应力场的影响          下载免费PDF全文

陈军  杜圣贤  张尚坤  贾超  刘凤臣  杨斌 《山东国土资源》2019,35(5)

包括恐龙化石在内的古生物化石是重要的地质遗迹,是研究生物进化的最重要资料。该文从物理力学角度,通过数值试验模拟分析围压和轴压作用下对恐龙化石强度和破坏特性的影响效果。试验结果表明:不同埋深时围压对含有不同角度裂隙化石应力影响较大,随着埋深增加,含有裂隙化石的应力大幅增大。在围压与轴压共同作用时,埋深对开裂角的影响较小,而随埋深增大时极限载荷也随之增大。同时,在不同埋深下开裂角随裂隙角度的变化趋势一致,均随着裂隙角度的增大而减小;而极限载荷随裂隙角度的变化趋势一致。  相似文献   

Two belts of HTLP sub-regional metamorphism in the New England Orogen,eastern Australia: occurrence and characteristics exemplified by the Wongwibinda Metamorphic Complex     

K. Jessop  N. R. Daczko  S. Piazolo 《Australian Journal of Earth Sciences》2020,67(4):479-507

Abstract

Two north–south-trending belts of high-temperature–low-pressure (HTLP) sub-regional metamorphism have been identified in the New England Orogen of eastern Australia. Metamorphic complexes in the ～1300?km long Early-Permian Inland belt have ages ca 300–290?Ma, and those of the ～400?km long Mid-Permian Coastal belt ca 275–270?Ma. These periods correspond to the beginning and end of an extended (early–mid Permian) phase of subduction rollback and crustal thinning in eastern Australia. This paper describes and incorporates recent work on the Wongwibinda Metamorphic Complex in the southern New England Orogen as a basis for comparison with thirteen other HTLP sub-regional occurrences within the orogen. These are described in as much detail as is currently available. Some outcrops of HTLP rocks in difficult terrain have been subject to limited study and only conditional comparisons can be made. However, a significant number of characteristics shared between the complexes including: their location at the higher-temperature end of broad areas of very low-grade to greenschist facies metamorphic rocks, indicative of tilted crustal blocks; their association with major shear zones; the presence of migmatite at the high-temperature end of a steep metamorphic field gradient; the presence of two-mica granite formed by the melting of the local sedimentary pile; and temporal association with S-type granites; imply a common extension-related mechanism of formation for these HTLP belts. The connection with major faults and shear zones suggests the belts trace major crustal-scale extensional structures that migrated eastwards from ca 300 to 270?Ma.

1. KEY POINTS

2. Two previously undocumented belts of HTLP subregional metamorphism are identified within the NEO.

3. Available dating indicates that metamorphism occurred along the belts at the beginning and end of a major early–mid Permian extensional phase in eastern Gondwana/Australia.

4. The characteristics of the HTLP complexes including their association with shear zones indicates they may delineate major loci of extension.

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考虑淤堵效应的疏浚淤泥真空固结沉降计算     

蔡袁强  周岳富  王鹏  史吏  王军 《岩土力学》2020,41(11):3705-3713

疏浚淤泥含水率高、强度极低，真空梯度作用下排水板周围会快速形成致密“土柱”，导致排水固结能力迅速下降，即出现淤堵现象。由疏浚淤泥真空固结室内模型试验获得了出水量变化情况和土体含水率、渗透系数的时空分布情况，确定了排水体周围淤堵区的形成时间与范围，提出了考虑时间效应与淤堵效应的真空度传递模式，同时考虑疏浚淤泥土体压缩和渗透的非线性，建立了考虑淤堵效应的固结分析模型，获得了相应的解析解，通过与已有数据和现场试验结果对比验证了该解答的有效性。利用该解析解，分析了真空度传递模式、淤堵系数λ和淤堵比c对沉降的影响。结果表明，淤堵效应明显减缓了沉降速率，也严重降低了疏浚淤泥的最终沉降量。  相似文献   

One-dimensional self-weight consolidation with continuous drainage boundary conditions: Solution and application to clay-drain reclamation     

Jianxue Feng  Pengpeng Ni  Guoxiong Mei 《国际地质力学数值与分析法杂志》2019,43(8):1634-1652

Traditional consolidation theories cannot provide good predictions of consolidation settlement in land reclamation because of their assumptions that the influence of soil's self-weight is often neglected, and the drainage boundary is considered as fully pervious/impervious. In view of these limitations, an analytical solution is derived for one-dimensional self-weight consolidation problems with a continuous drainage boundary using the finite Fourier sine transform method. Following the classical Terzaghi's small strain theory, the soil's self-weight is considered to produce consolidation settlement in dredged materials with a constant coefficient of consolidation. The continuous drainage boundary can essentially describe the time-dependent variation of drainage capacity at the interface between two adjacent soil layers. By reducing the interface parameters, the effectiveness of the calculation is demonstrated against the Terzaghi's solution. The influence of interface parameters and soil's self-weight stress coefficient on self-weight consolidation is discussed. As expected, the rate of consolidation considering the self-weight stress is faster, although the dependency of consolidation rate on the material property of void ratio is neglected. Moreover, the plane of maximum excess pore-water pressure is estimated as a function of time factor, based on which a design chart is developed to optimize the layout of horizontal drains in land reclamation.  相似文献   

高压旋喷多管喷头的研制          下载免费PDF全文

罗帅训  赵建勃  贺雪峰  韦波锋 《探矿工程》2020,47(7):78-81,87

基于高压旋喷成桩机理以及目前市场对大桩径施工的需求，针对普通旋喷施工成桩直径小、排泥污染环境等问题，研制了一款能适应新工艺、新工法且能解决上述问题的多管喷头。通过对喷头在地下工作的实际状态进行分析，新研制的多管喷头具有地内压力检测、专用通道排泥及浆管通径大等特点，可以实现大桩径施工、泥浆可统一回收及避免施工对周边建筑的扰动。  相似文献   

Relation between mean stress,thermodynamic, and lithostatic pressure     

Evangelos Moulas  Stefan M. Schmalholz  Yury Podladchikov  Lucie Taj manov  Dimitrios Kostopoulos  Lukas Baumgartner 《Journal of Metamorphic Geology》2019,37(1):1-14

Pressure is one of the most important parameters to be quantified in geological problems. However, in metamorphic systems the pressure is usually calculated with two different approaches. One pressure calculation is based on petrological phase equilibria and this pressure is often termed thermodynamic pressure. The other calculation is based on continuum mechanics, which provides a mean stress that is commonly used to estimate the thermodynamic pressure. Both thermodynamic pressure calculations can be justified by the accuracy and applicability of the results. Here, we consider systems with low‐differential stress (<1 kbar) and no irreversible volumetric deformation, and refer to them as conventional systems. We investigate the relationship between mean stress and thermodynamic pressure. We discuss the meaning of thermodynamic pressure and its calculation for irreversible processes such as viscous deformation and heat conduction, which exhibit entropy production. Moreover, it is demonstrated that the mean stress for incompressible viscous deformation is essentially equal to the mean stress for the corresponding viscous deformation with elastic compressibility, if the characteristic time of deformation is five times longer than the Maxwell viscoelastic relaxation time that is equal to the ratio of shear viscosity to bulk modulus. For typical lithospheric rocks, this Maxwell time is smaller than c. 10,000 years. Therefore, numerical simulations of long‐term (>10 kyr) geodynamic processes, employing incompressible deformation, provide mean stress values that are close to the mean‐stress value associated with elastic compressibility. Finally, we show that for conventional systems the mean stress is essentially equal to the thermodynamic pressure. However, mean stress and, hence, thermodynamic pressure can be significantly different from the lithostatic pressure.  相似文献   

基于扩展有限元方法的裂隙岩体冻胀力理论与数值研究     

马伟  谭贤君  陈卫忠  周云 《冰川冻土》2020,42(2):532-539

为研究寒区裂隙岩体内冻胀力的变化规律， 从单裂隙入手， 基于弹性力学、 水冰相变理论以及质量守恒关系， 建立了考虑未冻水含量及水分迁移的冻胀力求解模型； 利用MATLAB平台编制程序， 采用扩展有限元方法（XFEM）计算得到了裂隙内冻胀力随冻结时间的演化规律。采用有效体积膨胀系数法计算得到的冻胀力数值解与理论模型计算结果以及其他学者的试验结果吻合较好， 并分析了水冰相变下裂隙尖端应力场， 数值计算结果与理论解吻合较好， 验证了数值方法的可靠性； 通过分析影响冻胀力发展的因素， 指出岩石弹性模量和裂隙几何形状是控制裂隙内冻胀力演化的两个重要因素。  相似文献   

岛礁吹填珊瑚砂力学行为与颗粒破碎特性试验研究     

吴杨  崔杰  李能  王星  吴毅航  郭舒洋 《岩土力学》2020,41(10):3181-3191

珊瑚砂是岛礁陆域吹填唯一的材料，因其特殊的海洋生物成因和孔隙结构特征，珊瑚砂颗粒在常规工程应力水平下就会发生破碎。通过对取自南海某吹填岛礁的珊瑚砂开展室内三轴固结排水剪切试验，研究珊瑚砂强度、变形参数和颗粒破碎程度随相对密实度、围压的演变规律，并与其他研究成果中的南海珊瑚砂强度参数进行对比分析。研究结果表明：珊瑚砂应变软化及剪胀特征随有效围压的增大、密实度的减小而逐渐减弱；在常规应力范围内，得到珊瑚砂峰值摩擦角和临界状态摩擦角的取值范围分别为33o～58o和28o～47o，且均随有效围压的增大而减小；建立了珊瑚砂割线模量E50与相对密实度、有效围压间的关系式；珊瑚砂峰值摩擦角与修正相对破碎指数Br*间的关系可用指数为负数的幂函数关系式拟合，且当颗粒破碎程度较高时，峰值摩擦角随修正相对破碎指数的增大而减小的趋势变缓；珊瑚砂修正相对破碎指数随塑性功的增大近似以双曲线的形式增长，密实度对两者间的关系影响不大。该研究成果可为南海岛礁基础设施的安全设计提供参考。  相似文献   

微型钢管桩在基坑支护中的应用          下载免费PDF全文

刘文峰 《探矿工程》2020,47(10):67-71

随着经济社会的快速发展，微型钢管桩作为一种支护结构在深基坑支护施工中的应用越来越多。本文根据微型钢管桩的施工工艺以及工程实践，总结了微型钢管桩应用于基坑支护工程的主要特点，结合工程应用实例分析了微型钢管桩在基坑支护工程中的作用及效果，表明在基坑周边环境条件受限和抢险加固等基坑支护工程中能充分发挥微型钢管桩的优点，具有显著的经济效益和社会效益  相似文献   

Porosity in chalk – roles of elastic strain and plastic strain     

Ida Lykke Fabricius 《Sedimentology》2020,67(7):3451-3470

Chalks originate as Cretaceous to Recent pelagic or hemipelagic calcareous ooze, which indurate via burial diagenesis to chalk and limestone. Because they accumulate in pelagic settings with high environmental continuity, chalks may form thick formations and even groups. For this reason, and because chalks have a simple mineralogy (low magnesium calcite, silica and clays), they are ideal for the study of diagenetic processes including the depth-related decrease of porosity. It is the aim of this study to illustrate how the evaluation of in situ elastic strain can help in understanding these processes including the interplay between stress-controlled diagenetic processes and processes furthered by thermal energy. Petrophysical core and well data can be used for analyses of how porosity reduction via pore collapse and pressure dissolution is related to in situ elastic strain. The data in question are: depth, density of overburden, pore pressure, ultrasonic P-wave velocity and dry density/porosity. The analysis reveals that the transition from ooze to chalk is associated with high elastic strain and consequent pressure dissolution at calcite–particle contacts causing contact cementation. The transition from chalk to limestone is also associated with high elastic strain, especially at clay–calcite interphases causing development of stylolites via pressure dissolution, and consequent pore-filling cementation. Following each transformation the elastic strain drops rapidly. The observation of this diagenesis-related pattern in elastic strain of the sedimentary rock is novel and should not only be helpful in understanding the porosity development in sedimentary basins, but also add basic scientific insight.  相似文献