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1.
条带开采中条带煤柱塑性区宽度分析   总被引:9,自引:0,他引:9  
根据煤的变形破坏特点,对煤变形采用弹塑性应变软化模型,根据条带开采的特殊性,用三维受力单元模型来分析。通过数学运算推导出条带煤柱塑性区应力及宽度的表达式。最后,对影响塑性区宽度的几个主要因素作了分析。  相似文献
2.
应变软化土质边坡渐进破坏的演化模型   总被引:8,自引:0,他引:8  
考虑到土体的流变效应 ,通过推广不平衡推力法 ,提出了具有应变软化性质的土质边坡渐进破坏的一个力学模型 .该模型采用Maxwell松驰模型描述局部破坏后滑裂面上土体的抗剪强度随时间的变化情况 ,用时间安全系数来描述边坡的稳定状态 ,并且不必假定渐进破坏从坡角开始 ,因而更接近实际情况 .通过数值模拟 ,清晰地揭示了边坡渐进破坏的历时演化过程 ,并证实了边坡的安全系数随时间推移而逐渐变小的规律  相似文献
3.
平面应变含缺陷岩样变形破坏全过程数值模拟   总被引:8,自引:2,他引:6  
采用拉格朗日元法(FLAC)研究了左边界有缺陷的压缩岩样剪切带的启动及演变规律,峰后本构关系采用线性应变软化模型.计算结果表明,在应力一时步曲线峰值之前,剪切带首先出现在缺陷附近,直到贯通试样右边界;在剪切带传播过程中,塑性区沿切向及法线向外扩展;剪切带内部单元的剪切应变率一时步曲线经历了稳定、线性上升和非线性上升3个阶段.然而,剪切应变增量随时步持续增加.剪切带倾角接近于Arthur倾角,表明数值计算结果是可信的。  相似文献
4.
A mechanical model for strain softening pillar is proposed considering the characteristics of progressive shear failure and strain localization. The pillar undergoes elastic, strain softening and slabbing stages. In the elastic stage, vertical compressive stress and deformation at upper end of pillar are uniform, while in the strain softening stage there appears nonuniform due to occurrence of shear bands, leading to the decrease of load-carrying capacity.In addition, the size of failure zone increases in the strain softening stage and reaches its maximum value when slabbing begins. In the latter two stages, the size of elastic core always decreases. In the slabbing stage, the size of failure zone remains a constant and the pillar becomes thinner. Total deformation of the pillar is derived by linearly elastic Hooke‘s law and gradient-dependent plasticity where thickness of localization band is determined according to the characteristic length. Post-peak stiffness is proposed according to analytical solution of averaged compressive stressaverage deformation curve. Instability criterion of the pillar and roof strata system is proposed analytically using instability condition given by Salamon. It is found that the constitutive parameters of material of pillar, the geometrical size of pillar and the number of shear bands influence the stability of the system; stress gradient controls the starting time of slabbing, however it has no influence on the post-peak stiffness of the pillar.  相似文献
5.
岩石软化的细观损伤模型   总被引:4,自引:0,他引:4  
通过分析岩石材料应变软化的细观损伤力学过程,建立了岩石软化阶段的细观损伤力学模型,从而得到单向拉伸状态下岩石软化过程的应力应变本构关系。  相似文献
6.
节理倾角对单节理岩样变形破坏影响的数值模拟   总被引:4,自引:1,他引:3  
采用FLAC模拟了节理倾角对各向异性岩样峰值强度、力学行为及剪切带图案的影响。节理由实体单元模拟。对于节理之外的岩石,采用莫尔库仑与拉破坏复合的破坏准则,峰后本构关系选择线性应变软化模型;对于节理,采用理想弹塑性的莫尔库仑准则。结果表明,无节理密实岩石的峰值强度最高。节理岩样的剪切应变或集中在节理上,或集中在新剪切带上,峰值强度随节理倾角而改变。新剪切带启动于节理的端部,然后沿其固有方向传播。当节理倾角适中时,节理岩样的峰值强度较低,岩样的行为受控于节理。当节理倾角较高或较低时,可观测到应变软化行为。若节理倾角较低,新剪切带的长度随节理倾角的降低而增加,这导致了陡峭的峰后应力-应变曲线。若节理倾角较高,由于节理倾角对新剪切带的厚度和倾角几乎没有影响,因此,峰后斜率不依赖于节理倾角。  相似文献
7.
应变软化及剪胀性土体中考虑大应变的孔扩张问题解析   总被引:3,自引:1,他引:2  
采用应力跌落模型模拟土体的应变软化,以Mohr-couloub屈服准则和不相关联的流动法则考虑土体屈服塑性流动和剪胀特性,引进对数应变考虑土体的大变形,给出了应变软化及剪胀性土体中考虑大应变的孔扩张问题的弹塑性解析解,为了对比,还给出了小应变情况下位移的解析表达式.分析了大、小应变理论、不同剪胀特性、不同软化程度和考虑塑性区弹性变形与否对结果的影响.结果表明:在孔扩张压力较大时,用小应变理论会引起很大误差,必须考虑大应变;在相同扩张力作用下,土体的软化程度越高,扩张率越大,土体的剪胀角越大则扩张率越小.土体的软化和剪胀特性还影响极限扩张压力,软化越严重,极限扩张压力越小;剪胀角越大,极限扩张压力越大.  相似文献
8.
土体应变软化特性的桩孔扩张弹塑性解析   总被引:2,自引:0,他引:2  
从土的基本工程性质出发,提出了考虑土的应变软化特性的线性弹塑性模型,并用以解析桩孔扩张条件下桩孔周边土体的应力应变及位移,分析了庆变软化状态到塑性流动的残余状态的强度准则的变化特征以及两个塑性区的存在方式,从理论上分析了桩孔扩张的反例-桩孔开挖应力释放条件下的桩孔壁土体状态与存在条件。  相似文献
9.
Considering the influence of strain softening, the solutions of stress, displacement, plastic softening region radius and plastic residual region radius were derived for circular openings in nonlinear rock masses subjected to seepage. The radial stress distribution curve, ground reaction curve, and relation curve between plastic softening region radius and supporting force in three different conditions were drawn respectively. From the comparisons among these results for different conditions, it is found that when the supporting force is the same, the displacement of tunnel wall considering both seepage and strain softening is 85.71% greater than that only considering seepage. The increase values of radial displacement at 0.95 m and plastic softening region radius at 6.6 m show that the seepage and strain softening have the most unfavorable effects on circular opening stability in strain softening rock masses.  相似文献
10.
Estimation of compaction grouting pressure in strain softening soils   总被引:2,自引:2,他引:0  
A new method was proposed to predict the limited compaction grouting pressure for the soft soils. Theoretical basis of the method considered the conical shear failure above the grout bulb. Using the Mohr-Coulomb yield criterion as the initial yield function, the limited compaction grouting pressure was determined, according to the softening elastic-plastic model based on the conventional triaxial compression tests to simulate the strain softening soils. The small strain in the elastic zone and large stain in the plastic zone and the rational yield function for the strain softening phase stage, the analytical solutions to the compaction grouting pressure were presented. The results indicate reasonable agreement and show a good potential of the proposed method for rationally optimizing the design of compaction grouting operations. Foundation item: Project (200550) supported by the Foundation for the Author of National Excellent Doctoral Dissertation of China; Project (09JJ1008) supported by Hunan Provincial Natural Science Foundation of China  相似文献
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