Retrospective and prospective review of the generalized nonlinear strength theory for geomaterials

Strength theory is the basic theory for calculating and designing the strength of engineering materials in civil,hydraulic,mechanical,aerospace,military,and other engineering disciplines.Therefore,the comprehensive study of the generalized nonlinear strength theory(GNST)of geomaterials has significance for the construction of engineering rock strength.This paper reviews the GNST of geomaterials to demonstrate the research status of nonlinear strength characteristics of geomaterials under complex stress paths.First,it systematically summarizes the research progress of GNST(classical and empirical criteria).Then,the latest research the authors conducted over the past five years on the GNST is introduced,and a generalized three-dimensional(3D)nonlinear Hoek‒Brown(HB)criterion(NGHB criterion)is proposed for practical applications.This criterion can be degenerated into the existing three modified HB criteria and has a better prediction performance.The strength prediction errors for six rocks and two in-situ rock masses are 2.0724%-3.5091%and 1.0144%-3.2321%,respectively.Finally,the development and outlook of the GNST are expounded,and a new topic about the building strength index of rock mass and determining the strength of in-situ engineering rock mass is proposed.The summarization of the GNST provides theoretical traceability and optimization for constructing in-situ engineering rock mass strength.

Assessing the range of blasting-induced cracks in the surrounding rock of deeply buried tunnels based on the unified strength theory

Blasting-induced cracks in the rock surrounding deeply buried tunnels can result in water gushing and rock mass collapse,posing significant safety risks.However,previous theoretical studies on the range of blasting-induced cracks often ignore the impact of the in-situ stress,especially that of the intermediate principal stress.The particle displacement−crack radius relationship was established in this paper by utilizing the blasthole cavity expansion equation,and theoretical analytical formulas of the stress−displacement relationship and the crack radius were derived with unified strength theory to accurately assess the range of cracks in deep surrounding rock under a blasting load.Parameter analysis showed that the crushing zone size was positively correlated with in-situ stress,intermediate principal stress,and detonation pressure,whereas negatively correlated with Poisson ratio and decoupling coefficient.The dilatancy angle-crushing zone size relationship exhibited nonmonotonic behavior.The relationships in the crushing zone and the fracture zone exhibited opposite trends under the influence of only in-situ stress or intermediate principal stress.As the in-situ stress increased from 0 to 70 MPa,the rate of change in the crack range and the attenuation rate of the peak vibration velocity gradually slowed.

Stability analysis of shallow tunnels subjected to seepage with strength reduction theory

Based on strength reduction theory,the stability numbers of shallow tunnels were investigated within the framework of upper and lower bound theorems of limit analysis. Stability solutions taking into account of water seepage were presented and compared with those without considering seepage. The comparisons indicate that the maximum difference does not exceed 3.7%,which proves the present method credible. The results show that stability numbers of shallow tunnels considering seepage are much less than those without considering seepage,and that the difference of stability numbers between considering seepage and without considering seepage increase with increasing the depth ratio. The stability numbers decrease with increasing permeability coefficient and groundwater depth. Seepage has significant effects on the stability numbers of shallow tunnels.

Rock strength interval analysis using theory of testing blind data and interval estimation

The concepts of rock strength intervals are presented in this work, furthermore, central values of intervals and their corresponding credibility are provided using two-case study based on blind data theory and fuzzy interval estimation. 60 granite specimens are first tested, the compressive strength interval and tensile strength interval are [ 103.68, 219.6 l ] and [7.53, 11,86] MPa, while the tested mean values of compressive strength and tensile strength are 152.86 and 10.14 MPa, the credibilities are less than 58.4% and around 70.4%, respectively, the credibility of shear strength is between 40% and 60%. Then 70 other rock specimens are designed and tested, the similar conclusions can be reached. The results show that the conventional definite values are the particular values within the intervals, and the credibility of them often fails to reach the high-precision engineering requirement. The results demonstrate the feasibility and application potential of this proposed algorithm for the engineering practice. The references for engineering value selection of rock strength under different credibility or according to frequency distribution of central values are provided to increase the reliability and precision of calculation.

New Asphalt Pavement Failure Criterion Based on Unified Strength Theory

This study aims to introduce an appropriate analytical method for asphalt pavement based upon unified strength theory （UST）. The traditional maximum shear stress strength theory （MSST） cannot describe the marked difference between tension strength and compressive strength or variable intermediate principal stress, which significantly affects the geotechnical materials. Our studies try to find a new asphalt pavement failure criterion that considers the influence of both tension-compression strength ratio and intermediate principal stress of asphalt mixture. In order to select a suitable theory on pavement material, the UST is introduced and compared with the traditional theory. Results show that the tension-compression strength ratio of asphalt mixture, which is used as a material parameter, dramatically affects the stress and stress distribution law in pavement; the pavement stress level increases dramatically after considering the intermediate principal stresses. Therefore, the UST which considers both tension-compression strength ratio and intermediate principal stress is more in line with the material characteristics of asvhalt pavement.

A novel limiting strain energy strength theory

With applied dislocation theory,the effects of shear and normal stresses on the slide and climb motions at the same section of a crystal were analyzed.And,based on the synergetic effect of both normal and shear strain specific energies,the concept of the total equivalent strain specific energy(TESSE)at an oblique section and a new strength theory named as limiting strain energy strength theory(LSEST)were proposed.As for isotropic materials,the plastic yielding or brittle fracture of under uniaxial stress state would occur when the maximum TESSE reached the strain specific energy,also the expressions on the equivalent stresses and a function of failure of the LSEST under different principal stress states were obtained.Relationship formulas among the tensile, compressive and shear yield strengths for plastic metals were derived.These theoretical predictions,according to the LSEST,were consistent very well with experiment results of tensile,compressive and torsion tests of three plastic metals and other experiment results from open literatures.This novel LSEST might also help for strength calculation of other materials.

Fundamental Issues Towards Unified Design Theory of Recycled and Natural Aggregate Concrete Components

In the past 20 years,recycled aggregate concrete(RAC),as a type of low-carbon concrete,has become a worldwide focus of research.However,the design methodology for RAC structural components remains a challenge.Consequently,demands for a unified design of natural aggregate concrete(NAC)and RAC components have been presented.Accordingly,this study analyses the necessity of a unified design theory and provides an in-depth demonstration of the strength determination,compressive constitutive relationship,and design method of concrete components.The coefficient of variation of RAC strength is found to be generally higher than that of NAC strength.The compressive and tensile strengths of RAC can be defined and determined using the same method as that used for NAC.The uniaxial compressive constitutive relationship between NAC and RAC has a unified mathematical expression.However,the elastic modulus of RAC decreases,and its brittleness exhibits an increasing trend compared with that of NAC.Finally,to unify the design formulae of RAC and NAC components for bearing capacity,modification factors for RAC components are proposed considering safety and reliability.Additionally,the feasibility of the proposed unified time-dependent design theory is demonstrated in terms of conceptual design and structural measures considering the effects of strength degradation and reinforcement corrosion.It is believed that this study enriches and develops the basic theory of concrete structures.

Incompleted Field Strength Calculation of the Potential Term Adopted from Landau-Ginzberg Theory Applied in Particle Physics

Completion of field strength calculation of the potential term originated in theories of condensed matter applied in particle physics is discussed.

Study on the biaxial tensile strength of special made concrete based on the Hill theory

This paper mainly studies on the biaxial tensile strength and its calculative formula of a special made concrete. According to the Hill theory and the uniaxial tensile experiment results, the expression of the concrete biaxial tensile strength is deduced, which is then combined with experiment data and checked. The result shows： the biaxial tensile strength of this kind of concrete is about 15%-30% lower than its uniaxial tensile strength, and the calculative value is basically consistent with the experiment value, with less than 11% difference. This kind of biaxial tension weakening effect is very important to the structure designs of concrete road. The author suggests further research.

Analysis of Young Girls’Eagerness to Spend for Disney Virtual Characters Based on Marketing Mix Theory

A virtual character is a design of a fictitious creature with distinctive characteristics created by people,and Disney virtual characters are those Intellectual Property(IP)images that appeared in Disneyland and Disney movies.This investigation aimed to explore why many younger females are keen to spend money on Disney virtual characters.This paper adopted the Marketing Mix Theory strategy(product,price,placement,and promotion(4P)),and the SWOT analysis method has been utilized.This paper investigated the relationship between the 4Ps and consumers’purchasing intentions,and it turned out that unique design and effective promotion in this Disney case would promote consumers’purchase intention,while the higher price and less accessible placements affected their purchase intentions.Thus,the high price and limited places somewhat inhibit customers’desire to buy;due to the attractiveness of the product itself and the promotion on the internet,the target consumers are still willing to consume.

基于均匀化理论与上限分析的膨胀土滑坡稳定性分析

在膨胀土和滑坡共同作用下,隧道洞口段施工更容易引发地表开裂甚至滑坡等工程灾害,在隧道内采用微型桩群防治滑坡比抗滑桩具有优势。本文基于均匀化理论与上限分析对某高速公路隧道洞口段膨胀土滑坡的稳定性进行计算,并评价微型桩群和削方卸载不同组合方式的处置效果,计算时将微型桩群及桩周土通过均匀化理论等效为符合摩尔库仑强度准则的等效加固体来,以此提高计算效率,最后通过对现场削方+微型桩群加固处置后的滑坡变形监测来验证计算的合理性,得出如下结论:相较于土的强度参数,等效加固体内摩擦角保持不变,黏聚力从26kPa提高到85.36kPa。处置前后的滑坡稳定性评价结果表明,不做处理时,滑坡滑动面从滑坡上方岩土交界面延续到隧道洞口前;仅采用微型桩群加固时,滑坡安全系数在1.17左右,滑动面从岩土交界面延续到隧道洞口后;同时采用微型桩群加固和削方卸载时,滑坡安全系数提高到1.26~1.28,滑动面上缘由土石交界面前移。现场变形监测表明地表变形与深层土体变形均不超过3mm,该措施能保障滑坡的稳定性,同时也验证了计算方法的合理性,可为同类工程提供参考。

非对称破坏模式下临坡地基的Meyerhof承载力新解

利用统一强度理论的平面应变强度方程,综合考虑中间主应力、基础至坡肩的水平距离、边坡高度和基底粗糙情况等因素,提出临坡地基坡面非对称破坏模式和坡底非对称破坏模式,继而建立条形基础下临坡地基新的Meyerhof承载力解答,给出具体应用步骤并开展理论退化分析与对比验证。研究表明:考虑坡后土体强度贡献所提出的非对称破坏模式更符合临坡地基的实际破坏形态;所得临坡地基Meyerhof承载力解答与文献模型试验和数值模拟均吻合良好;中间主应力可明显提高临坡地基的承载力;临坡地基承载力随边坡高度增加先减小后恒定。研究结果合理反映了土体强度的中间主应力效应、破坏模式的非对称性以及基础旁侧土体强度等工程实际情况,对临坡地基优化设计具有一定的理论指导意义。

考虑中间主应力影响的非饱和黄土边坡抗滑桩间距研究

理论研究和工程应用中土体破坏准则的合理选用对研究和设计结果影响较大,同时由于中间主应力效应的影响,导致平面应变试验和常规三轴试验的试验结果的差异也被广泛证实。基于土拱破坏理论,采用理论推导的方式将统一强度理论、统一滑移线场理论和土拱破坏理论应用于非饱和黄土边坡抗滑桩间距研究中,并根据试验数据确定了非饱和黄土中间主应力参数b,推导了基于土拱理论的非饱和黄土边坡抗滑桩间距表达式。通过工程实例研究了非饱和黄土边坡抗滑桩间距随中间主应力参数b和基质吸力的变化规律。研究结果表明,考虑中间主应力效应的影响可增大抗滑桩设计间距,从而降低工程造价。研究对优化非饱和黄土地区抗滑桩间距具有重要的参考价值。

考虑温度和时间双重影响的混凝土蠕变模型构建

为了研究温度对混凝土结构蠕变特性的影响,开展不同温度作用下混凝土三轴蠕变试验,分析了不同温度作用下混凝土结构的轴向蠕变特性。在温度作用下,混凝土的内部损伤与非均匀程度参数有关,建立非均匀程度参数与温度之间的关系;假定混凝土蠕变模型是关于温度和时间的函数,结合上述损伤变量和微元体强度分布概率模型,建立了考虑温度和时间双重影响的混凝土蠕变模型。基于最小二乘法和试验数据对模型的准确性进行验证,并采用西原模型对其优越性作进一步验证。结果表明:不同温度作用下蠕变损伤模型与试验数据的吻合度都较好,且相关性系数在0.95以上,说明了所建立模型的正确性;同时,该模型与试验数据的吻合度要优于西原模型,并且在描述加速蠕变方面具有一定的优越性。该理论模型为地下工程中混凝土支护结构的长期变形预测研究提供理论依据。

美国公众对中美科技实力认知的情感控制研究——基于“寰球民意指数”(2023)调查数据的分析

国家间科技实力的较量在大国博弈中作用显著,也是影响中美关系的重要变量。基于“寰球民意指数”(2023)调查数据,本文探讨了美国公众对中美科技实力的比较性认知及其影响因素。研究发现,在情感控制论的认知框架下,受访者对中国大国地位评价越积极,越认可中国的科技实力,但这种认知呈现出内部分裂的特质,积极与消极并存。美国政府对中国科技政策的损己效能显著影响公众对中美科技实力比较的认知,国际事务关注度则对中国科技实力的认知具有消极影响。研究勾勒了美国公众对中国科技实力和形象认知的民意轮廓,为我们思考跨文化情境下国际公众的情感政治基础提供了分析框架。

基于统一强度理论的扰损围岩巷道脆塑性解答

钻爆法施工常造成岩质巷道扰损区围岩性能劣化。针对扰损围岩、扰损外围岩的弹塑性状态下不同的扰损围岩巷道力学模型,采用统一强度理论、弹-脆-塑性模型和非关联流动法则,建立扰损围岩巷道有关应力、位移和塑性区半径的脆塑性解答,探讨巷道力学模型的转换路径及判定方法,并将结果进行对比、验证,获得各因素的影响规律。研究表明:提出的巷道脆塑性解答合理反映了中间主应力、围岩扰损范围和峰后强度、剪胀特性的综合影响,通过参数组合变换可退化为多种解答并得到正确性验证,具有重要的理论意义和应用前景;巷道力学模型判定与中间主应力、围岩扰损范围密切相关,显著影响巷道应力-位移分布和围岩特征曲线;支护压力和巷道稳定变形随着围岩峰后强度下降、剪胀特性参数增加而明显增大。

早期目标导向活动对机械通气患者短期预后的应用研究

目的探讨早期目标导向活动在重症加强护理病房(ICU)机械通气患者中应用的短期预后效果。方法采用便利抽样法,选取76例机械通气患者作为研究对象,以病区为单位,入住ICU A区的38例患者为对照组,实施常规康复护理方案;入住ICU B区的38例患者为实验组,采用Richmond躁动-镇静评分、标准化5问题问卷、ICU活动量表评估研究对象镇静程度、配合程度及ICU活动能力,实施早期目标导向活动。观察2组患者肌力及握力水平、ICU活动能力、机械通气时间及ICU住院时间。结果干预第4 d及出科前实验组肌力、握力及出科前的活动能力得分高于对照组(P<0.05);实验组机械通气时间及ICU住院时间短于对照组(P<0.05)。结论早期目标导向活动有助于提高机械通气患者的肌力、活动能力,缩短ICU停留时间,改善患者短期预后。未来可进一步随访,探究早期目标导向活动的远期效果,为早期目标导向活动的推广及应用提供临床指导。

论中国本土的执行理论与实践

在中国,执行是政治意图及其实现的全过程,涉及公共权力系统的全部运作,极富中国本土特色。中国的执行可以提炼为一个由“政治意图”“具体化”“部门化和本土化”“可操作化”“操作”“影响环境”以及“反馈和调整”七个环节构成的闭环结构,这一结构可以视为一个全新的本土化分析框架和理论模型。新的框架清晰表达了中国执行背后的独特运作特征,充分揭示了中国政治体制守正变通的显著优势所在。中国的执行既是整体协调、一体运作的政治杰作,又是单独成篇、羽化成蝶的精彩过程。然而,在中国执行体制中,从政治意图的传递到最后实现实际还有多个“断点”“堵点”和“痛点”,执行的技术操作和经验积累还相对不足,仍需在改革实践和制度建设中补齐弱项短板,加以不断发展完善。

中国典型集体离职案例的思考与启示——基于事件理论分析改革开放40余年来的典型案例

企业员工集体离职对相关组织和员工群体影响深远。研究以1978年至2021年中国改革开放的43年为时间背景,从中国知网(CNKI)的5个子数据库中甄选出我国集体离职案例102个和典型集体离职案例16个。基于编码分析、事件分析等案例研究方法,主要发现:典型集体离职案例的事件强度在新颖度、中断度、重要度中占据其一,即具有代表性;事件空间主要受所在企业规模、行业地位、社会影响力等因素影响;事件时间主要受集体离职人员的层级、重要性、不可替代性等因素影响。分析典型集体离职案例既要考虑时代背景、法律变迁、文化冲突等宏观因素——这些因素可能诱发集体离职;更要考虑外部诱惑、股东更替、高管套现等微观因素——这些因素可能直接导致集体离职。集体离职的发生受到中国改革开放进程的影响:发生地呈现由沿海向内陆变迁的趋势;所涉行业多集中在制造业,这一点尤其在中国加入世贸组织后更加明显;离职人员所涉层级由高层向中层和基层扩展,同时涉及高层、中层和基层的连带离职对企业影响更大。研究还提炼出影响集体离职的宏观因素和微观因素的作用与特征模型,并有针对性地提出预防集体离职事件发生的意见建议。

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。