Crack nucleation in saturated porous media     

Luc Dormieux  Eric Lemarchand  Thomas Carlioz  Laurent Jeannin 《国际地质力学数值与分析法杂志》2020,44(5):553-574

Crack nucleation has been the subject of important contributions in the last two last decades. However, it seems that few attention has been granted to the case of saturated porous media. This is the question addressed in the present paper which is devoted to nucleation in traction mode. From a physical point of view, nucleation is a sudden phenomenon, so that the material response is both adiabatic and undrained. In the spirit of the variational approach, the nucleated crack is viewed as the final state of a region of space in which the material undergoes a full damage process. In traction mode, the opening of a saturated crack in undrained condition induces a drop of fluid pressure. In case of low fluid compressibility, the presence of the fluid delays the brittle failure usually associated with nucleation, as long as the fluid pressure remains above the saturation vapor pressure. Nucleation is therefore possible only if a partial vaporization of the fluid takes place.  相似文献   

Moment Magnitude and Its Calculation     

Chen Yuntai  Liu Ruifeng 《中国地震研究》2018,32(4):447-455

In this paper, we give a brief introduction to the proposal and development history of the earthquake magnitude concept. Moment magnitude M_W is the best physical quantity for measuring earthquakes. Compared with other magnitude scales used traditionally, moment magnitude is not saturated for all earthquakes, regardless of big and small earthquakes, deep and shallow earthquakes, far field and near field seismic data, geodetic and geological data, moment magnitude can be measured, and can be connected with well-known magnitude scales such as surface wave magnitude M_S. Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is the preferred magnitude selected by the International Seismological community, and it is preferred by the departments responsible for publishing seismic information to the public.Moment magnitude is a uniform magnitude scale, which is suitable for statistics with wide magnitude range. Moment magnitude is a preferred magnitude for international seismology, it is preferred by the agency responsible for providing information about earthquakes to the public. We provide all formulas used in the calculation of moment magnitude, and the calculation steps in detail. We also analyzed some problems and rules to solve these problems by using different formulas and numerical value calculation steps.  相似文献   

Dynamic responses of unsaturated half‐space soil to a moving harmonic rectangular load          下载免费PDF全文

Zheng Lu  Ran Fang  Hailin Yao  Cheng Dong  Shaohua Xian 《国际地质力学数值与分析法杂志》2018,42(9):1057-1077

The problem of the dynamic responses of a semi‐infinite unsaturated poroelastic medium subjected to a moving rectangular load is investigated analytical/numerically. The dynamic governing equations are obtained with consideration of the compressibility of solid grain and pore fluid, inertial coupling, and viscous drag as well as capillary pressure in the unsaturated soil, and they can be easily degraded to the complete Biot's theory. Using the Fourier transform, the general solution for the equations is derived in the transformed domain, and then a corresponding boundary value problem is formulated. By introducing fast Fourier transform algorithm, the unsaturated soil vertical displacements, effective stresses, and pore pressures induced by moving load are computed, and some of the calculated results are compared with those for the degenerated solution of saturated soils and confirmed. The influences of the saturation, the load speed, and excitation frequency on the response of the unsaturated half‐space soil are investigated. The numerical results reveal that the effects of these parameters on the dynamic response of the unsaturated soil are significant.  相似文献   

含流体致密砂岩的纵波频散及衰减:基于双重双重孔隙结构模型描述的特征分析          下载免费PDF全文

郭梦秋  巴晶  马汝鹏  陈天胜  张琳  庞孟强  谢剑勇 《地球物理学报》2018,61(3):1053-1068

致密砂岩普遍具有低孔、低渗及微裂缝发育的地质特征，并且呈现出很强的非均匀性.致密砂岩储层与常规砂岩储层比较，具有明显的岩石物理性质、渗流力学性质方面的差异.致密砂岩内部的非均匀性对弹性波频散、衰减有显著影响，其中包括孔隙结构的非均匀性，即岩石内部孔隙参数的不均一性，以及孔隙内部不相混溶流体的非均匀分布；此外，非均匀性的尺度也决定了波出现显著频散与衰减的频段.综合考虑致密砂岩孔隙结构非均匀性及流体斑块状饱和的非均匀性，本文采用双双重孔隙介质结构模拟了致密砂岩的弹性波响应，分析了同时具备两类非均质性岩石中的波传播特征.调查分析了两组分别来自中国鄂尔多斯盆地苏里格气田及四川盆地广安气田的不同类型致密砂岩储层的岩芯超声波实验数据，给出了岩石样本的弹性波速度频散与衰减曲线.结果显示理论模型预测结果与完全饱和、部分饱和岩石的实验数据吻合良好.对两个地区致密砂岩岩芯数据进行对比分析，苏里格致密砂岩样本总体上比广安致密砂岩渗透率高，在各孔隙度范围内，特征模拟显示苏里格样本的裂隙尺寸明显大于广安样本.广安致密砂岩在低孔隙度范围内发育了更多、更小的颗粒裂隙/接触.致密砂岩的速度频散与衰减结果受流体黏度、晶体破裂及流体斑块状饱和的共同影响.此外，孔隙度越大，部分饱和岩石中斑块状饱和机制对总衰减的贡献越低，与之相对，结构非均质性所占的比重则有所增强.  相似文献   

Micromechanical approach to swelling behavior of capillary-porous media with coupled physics     

Mahdad Eghbalian  Mehdi Pouragha  Richard Wan 《国际地质力学数值与分析法杂志》2019,43(1):353-380

A detailed multiscale analysis is presented of the swelling phenomenon in unsaturated clay-rich materials in the linear regime through homogenization. Herein, the structural complexity of the material is formulated as a three-scale, triple porosity medium within which microstructural information is transmitted across the various scales, leading ultimately to an enriched stress-deformation relation at the macroscopic scale. As a side note, such derived relationship leads to a tensorial stress partitioning that is reminiscent of a Terzaghi-like effective stress measure. Otherwise, a major result that stands out from previous works is the explicit expression of swelling stress and capillary stress in terms of micromechanical interactions at the very fine scale down to the clay platelet level, along with capillary stress emerging due to interactions between fluid phases at the different scales, including surface tension, pore size, and morphology. More importantly, the swelling stress is correlated with the disjoining forces due to electrochemical effects of charged ions on clay minerals and van der Waals forces at the nanoscale. The resulting analytical expressions also elucidate the role of the various physics in the deformational behavior of clayey material. Finally, the capability of the proposed formulation in capturing salient behaviors of unsaturated expansive clays is illustrated through some numerical examples.  相似文献   

应力路径和干湿状态对堆石料颗粒破碎的影响研究     

孔宪京  宁凡伟  刘京茂  邹德高  周晨光 《岩土力学》2019,40(6):2059-2065

堆石料颗粒破碎是引起高土石坝变形的重要因素。在大坝填筑、蓄水期，堆石料的应力路径和干湿状态均是变化的。通过大型三轴试验，系统地研究了应力路径和干湿状态对堆石料颗粒破碎规律的影响。试验结果表明：（1）相同初始条件下，按不同应力路径达到同一轴向应变停机时测定的颗粒破碎率是不同的，等围压?3试验产生的颗粒破碎最大，等平均主应力p试验的次之，等最大主应力?1试验的最小，但不同应力路径下的颗粒级配演化规律是一致的。（2）相同初始条件下，湿样的颗粒破碎率明显高于干样，且二者的差距随着围压的增大而增大，不同干湿条件下的颗粒级配演化规律同样是一致的。（3）建立的考虑母岩强度的颗粒破碎率与塑性功的关系可以较好地统一描述不同应力路径及干湿状态下的颗粒破碎。该研究成果可为建立复杂应力路径及干湿变化条件下考虑颗粒破碎的堆石料弹塑性本构模型提供依据。  相似文献   

3D打印技术在岩石物理力学试验中的应用     

刘泉声  何璠  邓鹏海  田永超 《岩土力学》2019,40(9):3397-3404

3D打印技术在岩土工程领域的应用还处于初步探索阶段，但其可重复制造含复杂内部结构的试样是常规室内试验无法实现的。现阶段制约3D打印技术在岩石物理力学试验中应用的主要因素在于3D打印试样强度偏低，延性较强。初步探讨了3D打印后干燥时间、打印胶水浓度对试样强度的影响，在此基础上提出了最优化打印方案，使打印试样在强度和脆性方面均有很大提升；通过改变打印方向模拟了天然层状节理岩石的各向异性特征。研究结果表明，随着打印倾斜角度的增加，3D打印试样的单轴抗压强度先减小后增大，呈“U”型变化趋势，抗拉强度也随打印方向的改变出现明显的各向异性特征，这与天然层状节理岩石相关研究成果相似。研究成果可为3D打印技术在岩土工程领域的推广和室内试验研究提供参考。  相似文献   

Sensitivity of the surface temperature to changes in total solar irradiance calculated with the WRF model     

《Geofísica Internacional》2014,53(2):153-162

The temperature sensitivity of the WRF model to changes in Total Solar Irradiance (TSI). The simulations were performed for a region centered over the North Atlantic Ocean, including portions of Eastern North America, Western Europe and Northwest Africa. Four simulations were run with different TSI values. Also, a fifth simulation was performed in which we varied the initial atmospheric conditions, in order to compare the effect on the temperature of both, changes in the TSI and initial atmospheric conditions. Comparing temperature monthly averages we found that changes in TSI and in the initial conditions have a measurable impact on temperature in the region of study. The sensitivity of the model using non-dimensional parameters was also estimated. The numerical experiments show some features that might allow to distinguish between the effects on the temperature due to changes in TSI from those caused by initial conditions. However, TSI changes are of the same order of magnitude than those of disturbances in the initial conditions. We also found that the mean monthly values of temperature over the full grid, did not present significant variations due to changes of either initial conditions or TSI.  相似文献   

鄂尔多斯盆地延安地区山西组山2段储层可动流体赋存影响因素分析     

刘江斌 《地质与勘探》2021,57(1):231-240

山2段是鄂尔多斯盆地延安地区致密砂岩气生产的重要层段,目前对其流体赋存规律认识明显不足。因此在铸体薄片、扫描电镜、X射线衍射、高压压汞、恒速压汞、核磁共振测试的基础上,分析该储层可动流体的赋存特征及其影响因素。结果表明:山2储层主要为岩屑石英砂岩和岩屑砂岩,溶蚀孔和晶间孔为主要储集空间,粒间溶孔显著发育。山2储层可动流体饱和度为34.74%～91.83%,平均为69.94%,T2谱多为双峰态,呈左低右高型。储层孔隙度、渗透率、孔隙类型、孔喉特征及胶结物影响可动流体饱和度。孔隙为可动流体提供主要空间,平均孔隙半径越大,平均喉道半径越大,孔喉比越小,可动流体饱和度越高。硅质含量越高,粒间孔保存越好,可动流体饱和度越高。铁方解石含量越高,孔隙破坏越明显,可动流体饱和越低。高岭石含量较高,长石溶孔及晶间孔发育较好,有利于流体流动,可动流体饱和度也较高。  相似文献   

不同初始饱和度红砂岩冻融后物理力学性质研究          下载免费PDF全文

沈世伟  吴飞  甘霖  姜满 《探矿工程》2021,48(1):120-128

对不同初始饱和度红砂岩冻融循环前后进行物理及力学试验研究,探讨初始饱和度对红砂岩冻融损伤的影响。本文设定红砂岩试样初始饱和度为20%、40%、60%、80%、100%,冻融次数设定为20次,对冻融前后试样分别测定质量、纵波波速以及进行单轴压缩试验。试验结果表明：1）冻融后不同初始饱和度红砂岩的物理性质发生变化,纵波波速降低、质量减小,但变化程度不同;2）随饱和度的增大,试样经冻融后峰值强度和弹性模量均呈降低趋势,但只有饱和度大于60%时,降低趋势较明显。本文研究为寒区隧道及地下工程建设以及岩土地质灾害监测与治理提供理论依据和试验基础。  相似文献