基于Mohr强度理论的双参数抛物线型屈服准则

从Mohr强度理论出发,对双参数强度理论进行分析,特别是对双参数抛物线型屈服准则进行研究,推导了双参数抛物线强度准则的多种表达形式,分析了该屈服准则在应力空间中的展布特征,证明了双参数抛物线准则在偏平面上分别以两种曲线形式出现,即分段抛物线和分段直线,两者在应力空间中是光滑连接的.两种曲线构成的屈服轨迹都含有角点,对角点进行了修圆处理.通过将该屈服准则嵌入有限元程序,实现了基于双参数抛物线型屈服准则的破坏计算分析.     

对岩土体屈服强度准则的探讨(Ⅰ)--理论与模型

对岩土体常用的单剪屈服强度准则、双剪屈服强度准则和三剪屈服强度准则进行了系统的论述，通过对单剪、双剪和三剪屈服强度准则进行转化，指出岩土的屈服强度准则一般可表达为t8=g(θσ)f(σm)的函数形式，阐明了单剪、双剪和三剪屈服强度准则的差异主要表现在g(θσ)函数的不同，并进一步解释了中间主应力σ2对岩土类材料屈服强度的影响。     

一个新的屈服准则及其推广

在现有Ｔｒｅｓｃａ屈服准则、Ｍｉｓｅｓ屈服准则和双剪应力屈服准则的基础上，提出了一个新的屈服准则，并建立了一个统一表达式。分析结果表明，所建立的屈服准则，体育馆了Ｔｒｅｓｃａ准则和Ｍｉｓｅｓ准则，以及介于二之间的一族屈服准则，这些准则不仅满足Ｄｒｕｃｋｅｒ公设的屈服面外凸性条件，而且与材料性质有关。即不同的材料对应不同的屈服准则，Ｔｒｅｓｃａ准则和Ｍｉｓｅｓ准则可作为本的特殊形式。     

三剪应力统一屈服准则研究

为克服单剪屈服准则仅考虑最大主切应力和双剪准则只考虑两个较大主切应力的缺点，以菱形十二面单元体为依据，同时考虑单元体上的三个主切应力τ13、τ12、和τ23、对材料屈服的影响，认为这三者的组合达到某一极值时，材料即出现屈服．提出了三剪应力统一屈服准则，三剪屈服准则可更大限度地发挥材料的强度潜力．该屈服准则比单剪屈服准则和双剪屈服准则更具有一般性．它还可以考虑单元体上所作用的全部剪应力的不同组合，从而构成外凸和非凸两大族屈服面．     

等效Mohr—Coulomb屈服准则在岩质边坡稳定性分析中的应用

基于等效Molar—Coulomb屈服准则原理，通过岩体材料参数的人工换算，实现其在有限元软件Ansys中的应用，并论证了转化后的材料参数与原参数的大小关系，即转化后参数恒比原参数小。结合算例分析，得知采用等效Molar—Coulomb屈服准则计算得到的岩质边坡安全系数偏小、保守，可用来模拟岩体材料；同时，对不同位移及应力工程精度要求的岩质边坡工程，提出采用不同屈服准则的建议。     

剪应力屈服准则的统一形式

本文建立了剪应力屈服准则的统一形式。这是一个以等腰八面体切向剪应力的两个分量为函数的屈服准则。说明了各种剪应力屈服准则是有联系的,屈服准则与所研究的材料相关。这个一般的屈服准则,可以还原为各种现已知道的剪应力屈服准则。     

基于双剪屈服准则的空心旋转圆盘弹塑性分析

为了分析空心旋转圆盘的弹塑性应力分布机理,采用双剪应力屈服准则对理想弹塑性材料、等厚度空心旋转圆盘进行了弹塑性应力分析.结果表明,空心旋转圆盘的径向应力随着弹塑性转速的增大而增加,随后却随着转速的进一步增大而减小;而环向应力随着弹塑性转速的增大一直趋于增加;塑性极限转速随着空心旋转圆盘的内外径比值的增大而减小.由于双剪应力屈服准则与Tresca屈服准则的屈服轨迹分别对应屈服轨迹的上限和下限,在结构设计中,基于双剪应力屈服准则的设计,能够充分发挥材料的潜能,而基于Tresca准则的设计则趋向于保守     

一种考虑主应力空间的岩石非线性真三轴强度准则

为评估岩石的真三轴强度特性,首先根据常规三轴试验岩石强度的变化规律,提出基于偏应力极值的非线性强度准则,并与12种岩石试验强度和4种典型岩石强度准则进行对比,发现该强度准则的预测值与试验强度非常接近,相关性系数R~2均在0.98以上,平均相对误差(MAPE,E_(MAP))均小于4%(除7号岩石为6.83%);该强度准则、指数准则、H-B准则、MM-C准则和D-P准则对所有12种岩石预测E_(MAP)的平均值分别为2.32%、2.43%、5.28%、7.39%和13.74%,说明该强度准则能够很好地预测不同类型岩石的强度,其预测精度略优于指数准则(岩石力学界认为预测精度较高的强度准则),远好于其他3种强度准则。在上述所建常规三轴强度准则的基础上,通过引入中主应力参数和罗德应力参数,构建考虑中主应力效应的真三轴强度准则,并与8种岩石的真三轴试验强度进行对比,该强度准则很好地反映了大主应力随中主应力的增加呈先增大后减小的变化规律,所得R~2均在0.9以上,其中5种岩石的R~2大于0.96;除了13和14号岩石(E_(MAP)分别为7.79%和4.84%),其余6种岩石的平均相对误差E_(MAP)均小于4%,说明该强度准则能够较好地预测岩石的真三轴试验强度,很好地反映了中主应力效应,具有良好的普遍适用性。子午面和偏平面的应力空间特征也说明该强度准则很好地反映了岩石的静水压力效应和中主应力对大主应力的影响规律。     

双τ^2屈服准则及其统一表达式

分析了三个主剪应力对材料屈服的影响，提出了双τ２屈服准则，并建立了一个统一表达式．分析结果表明，所建立的屈服准则，包含了Ｍｉｓｅｓ准则和双剪应力屈服准则，以及介于二者之间的一族屈服准则．这些准则不仅满足Ｄｒｕｃｋｅｒ公设的屈服面外凸性条件，而且与材料性质有关，即不同的材料对应着不同的屈服准则，Ｍｉｓｅｓ准则和双剪应力准则均为该统一表达式的特殊形式．     

脆性岩石真三轴能量强度准则研究

基于岩石材料拉压强度不等和中间主应力对强度影响特点,从可释放弹性能角度出发推导和建立了可考虑中间主应力对岩石破坏弹性能释放影响的真三轴能量强度准则,利用厚壁圆筒试验数据和已有文献真三轴试验数据以及从能量准则参数物理含义三方面分析验证了所建真三轴能量强度准则的合理性及可靠性.结果表明,所建真三轴能量准则能适应于厚壁圆筒及真三轴压力试验的多种复杂应力状态;花岗岩、石灰岩中间主应力影响大于红砂岩、中细砂岩;对同种岩石来说,岩石中间主应力影响系数随应力状态不同而不同,总体变化趋势随中间主应力增加而先增大后减小;岩石能量强度准则与岩石应力状态和材料物理性质密切相关.     

平面应变条件下基于Lade-Duncan强度准则中主应力条件的土压力及其适用性

针对实际工程中大量存在的挡土墙、基坑开挖等平面应变问题,考虑中主应力对强度的影响,将平面应变条件下Lade-Duncan强度准则的中主应力关系代入SMP、Lade-Duncan、AC-SMP和广义Mises强度准则中得到新的平面应变强度准则。据此建立基于各强度准则的主、被动土压力计算公式,进而推广至黏性土,并将主、被动土压力理论计算值与实测值进行对比分析。结果表明,Mohr-Coulomb强度准则因其未考虑中主应力的影响,致使计算结果相比实测情况偏保守;SMP强度准则、Lade-Duncan强度准则考虑到中主应力对土压力大小的影响,计算结果相比Mohr-Coulomb强度准则更接近实测情况;AC-SMP强度准则、广义Mises强度准则在一定内摩擦角范围内可以描述挡土墙的土压力大小,但超出适用范围时,二者均不再适用于描述挡土墙的土压力大小;广义Mises强度准则在适用范围内的计算结果相比SMP强度准则、Lade-Duncan强度准则更接近实测数据。     

基于三剪屈服准则的材料弹塑性统一本构方程

为了改进双剪统一强度理论公式的分段表达,克服双剪统一弹塑性本构模型在θ=θb点上的双重滑移角现象,考虑十二面体单元上所有三个主剪应力共同作用的三剪屈服准则建立了材料的弹塑性统一本构方程,该弹塑性统一本构方程适合于服从Tresca屈服准则到Von Mises屈服准则的全部材料。     

Electromagnetic radiation early warning criterion of rock burst based on statistical theory

Rock bursts are serious natural disasters encountered worldwide in coal mining and rock engineering.In order to forecast rock bursts more effectively,a new rock burst forecasting index E,consisting of intensity and the number of pulses,is proposed,on the basis of abnormal characteristic symptoms of electromagnetic radiation(EMR)generated before rock bursts,combined with statistical theory.The index is distributed as a X2 distribution with 2 degrees of freedom,i.e.,E～X2(2).Via this index,a quantitative comprehensive forecasting criterion of EMR was initially established.E values were calculated when the occurrence probability of the occurrence of a rock burst was 50%,70% and 90%.Appropriate measures should be taken when using these values on the scene.Using EMR data collected in the Nanshan Mine of the Hegang mining area,we verified that the analytical result were consistent with actual situations.This index is of theoretical importance and as a reference for forecasting rock bursts in coal mines.     

Elasto-plastic analysis of the surrounding rock mass in circular tunnel based on the generalized nonlinear unified strength theory

The present paper aims to establish a versatile strength theory suitable for elasto-plastic analysis of underground tunnel surrounding rock. In order to analyze the effects of intermediate principal stress and the rock properties on its deformation and failure of rock mass, the generalized nonlinear unified strength theory and elasto-plastic mechanics are used to deduce analytic solution of the radius and stress of tunnel plastic zone and the periphery displacement of tunnel under uniform ground stress field. The results show that: intermediate principal stress coefficient b has significant effect on the plastic range,the magnitude of stress and surrounding rock pressure. Then, the results are compared with the unified strength criterion solution and Mohr–Coulomb criterion solution, and concluded that the generalized nonlinear unified strength criterion is more applicable to elasto-plastic analysis of underground tunnel surrounding rock.     

Failure criterion for soft rocks considering intermediate principal stress

The significant differences between hard rocks(more brittle) and soft rocks(more ductile) may suggest the use of different failure criteria. A strength criterion for soft rocks that includes intermediate principal stress was proposed. The new criterion includes two independent parameters: the uniaxial compressive strength(rci), which can be obtained from common laboratory tests or indirectly estimated by alternative index tests in the laboratory or field; and f(joint), which is used to characterize the rock mass quality and can be easily estimated. The authors compared the predictive capabilities of the new criterion with other criteria using the database of soft rocks under two conditions: with and without triaxial data. For the estimation of triaxial and true-triaxial strengths, the new criterion generally produced a better fit. The proposed criterion is practical for an approximate first estimation of rock mass strength, even without triaxial data, as it balances accuracy(lower prediction error) and simplicity(fewer independent parameters).     

Modified Mohr-Coulomb strength criterion considering rock mass intrinsic material strength factorization

With the increase of mining depth of mineral resources,the rock mass stress state is being more and more complex.The rock mass show different features,namely,with the increase of hydrostatic pressure,rock mass failure mode turns from brittle tension failure to structure ductile failure and its limit strength also increases.The restriction of minimal principal stress on the initiation and development of microcrack and the change of micro-unit stress state by the intermediate principal stress play a decisive role in the increase of rock mass limit strength.Based on the rock mass failure behavior law under complex stress state and theσ2-dependence on the rock mass strength,we proposed a Modified Mohr-Coulomb(M-MC)strength criterion which is smooth and convex.Finally,the M-MC criterion is validated by multiaxial test data of eight kinds of rock mass.We also compared the fitting results with Mohr-Coulomb criterion(MC).It shows that the new criterion fits the test data better than the Mohr-Coulomb criterion.So the M-MC strength criterion well reveals the rock mass bearing behavior and can be widely used in the rock mass strength analysis.The results can provide theoretical foundations for stability analysis and reinforcement design of complex underground engineering.