A hydraulic fracture height mathematical model considering the influence of plastic region at fracture tip

To predict fracture height in hydraulic fracturing, we developed and solved a hydraulic fracture height mathematical model aiming at high stress and multi-layered complex formations based on studying the effect of plastic region generated by stress concentration at fracture tip on the growth of fracture height. Moreover, we compared the results from this model with results from two other fracture height prediction models(MFEH, Frac Pro) to verify the accuracy of the model. Sensitivity analysis by case computation of the model shows that the hydraulic fracture growth in ladder pattern, and the larger the fracture height, the more obvious the ladder growth pattern is. Fracture height growth is mainly influenced by the in-situ stresses. Fracture toughness of rock can prohibit the growth of fracture height to some extent. Moreover, the increase of fracturing fluid density can facilitate the propagation of the lower fracture tip.

Computer Simulation of Plastic Deformation in GrainBoundary Region under High Rate Loading

The computer simulation of Al three-dimensional crystallite containing grain boundary of special type was carried out and its behaviour under high rate loading was investigated. The molecular dynamics method was used and interaction betwen atoms was described based on pseudopotential method. Vortical character of the atom movements in the grain boundary region is realized under shear loading in certain directions. Back and forth movements of atoms in the direction which is perpendicular to the shear also arise. Amplitude of such movements is approximately equal to an interplanar distance in this direction.

PERFECTLY PLASTIC FIELDS AT A RAPIDLY PROPAGATING PLANE-STRESS CRACK TIP

Under the condition that all the perfectly plastic stress components at a crack tip are the functions of only, making use of the Mises yield condition , steady-state moving equations and elastic perfectly-plastic constitutive equations, we derive the generally analytical expressions of perfectly plastic fields at a rapidly propagating plane-stress crack tip. Applying these generally analytical expressions to the concrete crack, we obtain the analytical expressions of perfectly plastic fields at the rapidly propagating tips of modes I and II plane-stress cracks.

EFFECTS OF MICROSTRUCTURE ON THE MACROSCOPIC ELASTO-PLASTIC PROPERTIES OF METAL MATRIX COMPOSITES

The generalized self-consistent finite-element iterative averaging method was adopted to analyze the elasto-plastic tensile properties of SiC whiskers reinforced aluminum matrix composites. The effects of varying fiber's aspect ratio and volume fraction on the macroscopic elasto-plastic deformation of the composites were studied. By the analysis of microscopic stress fields, the relation between the propagation of the elasto-plastic region in the matrix and the macroscopic elasto-plastic deformation of composites was discussed. It was found that the propagation of the plastic region in the matrix between the fiber's ends would affect prominently the elasto-plastic tensile behaviour of the composites. It was shown that the characterization of the stress-strain response in terms of the 0.2% offset yield strength is incomplete.

The cumulative analgesic effect of repeated electroacupuncture involves synaptic remodeling in the hippocampal CA3 region

In the present study, we examined the analgesic effect of repeated electroacupuncture at bilateral Zusanfi （ST36） and Yanglingquan （GB34） once a day for 14 consecutive days in a rat model of chronic sciatic nerve constriction injury-induced neuropathic pain. In addition, concomitant changes in calcium/calmodulin-dependent protein kinase II expression and synaptic ultrastructure of neurons in the hippocampal CA3 region were examined. The thermal pain threshold （paw withdrawal latency） was increased significantly in both groups at 2 weeks after electroacupuncture intervention compared with 2 days of electroacupuncture. In ovariectomized rats with chronic constriction injury, the analgesic effect was significantly reduced. Electroacupuncture for 2 weeks significantly diminished the injury-induced increase in synaptJc cleft width and thinning of the postsynaptJc density, and it significantly suppressed the down-regulation of intracellular calcium/ calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. Repeated electroacupuncture intervention had a cumulative analgesic effect on injury-induced neuropathic pain reactions, and it led to synaptic remodeling of hippocampal neurons and upregulated calcium/calmodulin-dependent protein kJnase II expression in the hippocampal CA3 region.

Complex regional pain syndrome: From diagnosis to rehabilitation

Complex regional pain syndrome(CRPS) is a debilitating pathology characterised by intense chronic pain associated with vasomotor, sensory and motor dysfunction of the affected limb. Although the pathophysiology of CRPS is not fully understood, it is recognised that inflammatory processes and autonomic dysfunction are involved. These processes are associated with peripheral and central sensitisation as well as changes in brain structure and function, and are reflected in the clinical presentation of CRPS. CRPS management requires an interdisciplinary team and requires the therapeutic approach to be individualised. With regard to pharmacological treatment, bisphosphonates, corticosteroids, ketamine and anticonvulsants have been demonstrated to be effective for CRPS management. Psychotherapy, including cognitive-behavioural therapy, has produced promising results but more studies are needed to confirm its efficacy. Among rehabilitation interventions, there is evidence of the efficacy of physiotherapy and occupational therapy in diminishing CRPS symptoms and achieving a higher level of functioning. In this regard, the rehabilitation modality that seems the most promising according to the actual literature is graded motor imagery, which can help to reverse the maladaptive neuroplasticity occurring in CRPS.

Ice-and cryogel-soil composites in water-retaining elements in embankment dams constructed in cold regions

There are a number of serious problems connected with building and repairing water-reining elements in embankment dams in cold regions. One of them is the difficulty in finding inexpensive clay materials with the necessary structural properties and using them in the winter. Another is the cracks that appear in the upper part of a dam when the core freezes to the banks, and leakage along the cracks threatens to desWoy the dam. Still another is the process of erosion at the bottom of the core which may occur through fissures in the rock foundation of a dam and in transport constructions. Also, the behaviour of water-retaining elements during eazthquakes is unreliable. All of these problems can be solved by using iceand cryogel-soil composites created by cryotropic gel formation （CGF）. Our laboratory investigations demonstrate that the materials proposed for water-retaining elements have the necessary permeable, plastic, thermophysical, and slrength properties to solve all of these problems. Certain consmactious of water-retaining elements which may prove to be both safe and cost-effective are proposed. However, these iceand cryogel-soil composites need to be field-validated before they are used in dams and transport structures in cold regions.

基于纤维梁柱单元的墩柱弹塑性性能数值分析模型

基于OpenSees开源平台,采用基于位移的纤维梁柱单元和零长度单元,建立了考虑钢筋混凝土墩柱塑性弯曲变形和粘结滑移效应的滞回推覆(Pushover)分析有限元模型,分析了塑性铰区单元长度对墩柱弹塑性性能数值模拟结果的影响,探讨了单元长度的合理取值,最后,基于美国PEER结构试验数据库中3个弯曲破坏的钢筋混凝土悬臂墩的拟静力试验结果,验证了数值模型的正确性。结果表明:采用基于位移的梁柱单元模拟钢筋混凝土墩柱弹塑性性能时,塑性铰区单元长度对其最大水平抗力和位移延性都有显著的影响;合理单元长度为等效塑性铰长度,而等效塑性铰长度可以采用Priestley等提出的经验公式计算。

基于生命周期评价的东北地区覆膜水稻环境影响分析

为探明覆膜水稻生命周期过程的资源消耗和环境影响,本研究基于2021—2022两年的田间试验对东北地区覆膜水稻进行生命周期评价。结果表明:仅考虑资源消耗、气候变化和环境酸化的情况下,覆PE膜旱直播水稻的环境影响潜值更小,对环境更友好。东北地区覆PE膜育秧移栽水稻能源消耗、水资源消耗、气候变化、环境酸化、富营养化和生态毒性6个环境影响指标对应的环境影响潜值分别为14046.40 MJ、957082.47 kg、1663.15 kg CO_(2)-eq、8.70 kg SO_(2)-eq、1.84 kg PO^(3-)_(4)-eq和57.05 kg 1,4-DCB-eq;东北地区覆PE膜旱直播水稻这6个环境影响指标对应的环境影响潜值分别为11990.32 MJ、312102.92 kg、1071.41 kg CO_(2)-eq、6.85 kg SO_(2)-eq、1.88 kg PO^(3-)_(4)-eq和73.75 kg 1,4-DCB-eq。造成资源消耗和气候变化的主要原因是氮肥和燃油的生产及使用,另外地膜生产和滴灌设备的生产也对环境造成了较大的影响。研究表明,水稻清洁生产的关键在于农资产品生产技术的优化和氮肥的合理施用。在两种覆膜水稻栽培方式中,覆膜旱直播水稻造成的环境影响更低,更适合我国农业绿色低碳发展。

塑性铰区ECC-钢管混凝土组合截面柱抗震性能研究

为研究塑性铰区ECC-钢管混凝土组合截面柱的抗震性能,完成了2根ECC-钢管混凝土组合截面柱和1根普通钢筋混凝土柱对比的低周反复水平荷载试验,并对试验结果得到的滞回曲线、骨架曲线、延性系数、残余位移、耗能能力等抗震性能指标进行量化分析。试验结果表明,与普通钢筋混凝土柱相比,塑性铰区ECC-钢管混凝土组合截面柱的承载力、刚度及耗能能力均有较大程度提高,残余位移也得到有效控制,ECC材料能够与钢管及钢管内部填充材料协同工作和共同变形。

塑料产业集群效应对区域经济发展的影响

本文首先对我国塑料产业的集群概况和影响效应做了初步的定性分析,随后采用区位熵方法对2019—2021年我国塑料产业的产业集群情况进行测算,接着利用邓氏灰色关联度模型研究塑料产业集聚对区域经济发展的作用效果。研究表明,塑料产业集群发展与区域经济增长表现出良好的相关性,塑料产业集聚能够促进区域经济水平的提高。最后,本文提出充分发挥塑料产业集群效应、全面推进区域经济协调发展的对策建议,对我国经济增长提质增效具有一定的实践意义。

基于健康行为改变整合理论的健康教育对颌面部外伤整形患者创面愈合的影响

目的:探讨基于健康行为改变整合理论(Integratedtheory of health behavior change,ITHBC)的健康教育对颌面部外伤整形患者创面愈合的影响。方法:选取2019年6月-2022年6月笔者医院收治的预行整形美容缝合术的102例颌面部损伤患者,按随机数字表法分为对照组和观察组,每组51例。对照组采用常规护理干预,观察组在对照组基础上采用基于ITHBC的健康教育。比较两组创面愈合优良率、并发症总发生率、满意度及心理状态和生活质量评分。结果:观察组创面愈合优良率高于对照组(P<0.05),观察组并发症总发生率低于对照组(P<0.05)。干预前,两组抑郁自评量表(Selfrating depression scale,SDS)评分、焦虑自评量表(Self-rating anxiety scale,SAS)评分及36项简明生活质量量表(36-item short form health survey,SF-36)各项评分比较,差异无统计学意义(P>0.05)。干预后,两组SDS、SAS评分均降低,且观察组低于对照组(P<0.05);两组SF-36各项评分均升高,且观察组高于对照组(P<0.05)。观察组满意度评分高于对照组(P<0.05)。结论:基于ITHBC的健康教育可有效减少颌面部外伤整形美容患者创面感染,促进创面愈合,改善患者心理状态及生活质量,患者满意度较高,临床应用效果较好。

不同区域粉土累积塑性应变预测模型

机场道基在长期服役过程中,不同区域粉土的累积塑性应变发展有显著差异。目前研究中鲜有考虑粉土区域性差异影响,尚未有预测模型能够对不同区域机场的道基粉土进行统一量化和预测。为确定影响粉土累积塑性应变的关键指标,有针对性地预测各区域粉土塑性应变,保证道基的长期服役性能,从华北地区3个不同机场取现场道基粉土,开展了不同区域和不同黏粒含量下粉土的动三轴试验,以揭示了不同条件下粉土累积塑性应变发展规律;通过SPSS灰色关联分析探究了不同区域粉土的矿物成分、颗粒级配、液塑限、最优含水率和最大干密度等指标与其循环荷载下最终累积应变的相关性,确定了黏粒含量为关键评价指标;基于试验结果建立了最终累积塑性应变预测模型。结果表明:不同区域粉土的颗粒级配、液塑限和最大干密度均有显著差异;循环荷载下累积塑性应变也差异显著,且受动应力影响;通过灰色关联分析,确定了以黏粒含量作为评价各地粉土最终累积塑性应变的量化指标;基于不同黏粒含量的动三轴试验结果,建立了考虑区域差异和动应力幅值的最终累积塑性应变预测模型。该预测模型能较好适用于不同区域机场道基粉土,基于当地粉土黏粒含量情况,较为准确地预测其长期服役过程中的累积塑限应变。

非对称荷载作用下土体劈裂注浆压力分析

为研究在非对称荷载作用下土体劈裂注浆压力,基于扩孔理论和统一强度准则并考虑非对称荷载的作用,建立基于扩孔理论的劈裂注浆启劈压力分析模型,推导出浆泡周围塑性区土体的应力场、位移场、塑性区半径以及启劈注浆压力的理论解答,并以工程算例进行论证。结果表明,考虑对称荷载作用下的启劈注浆启劈压力较考虑非对称荷载作用下的值要大,对称荷载作用下的分析方法低估了塑性区半径;无论是柱形劈裂还是球形劈裂,当K 0 1时,启劈压力会随着K 0的增大而增大,塑性半径会随着K 0的增大而明显减小;当K 0 1时,启劈压力会随着K 0的增大而减小,而塑性半径的变化是有限的。预先了解土体的初始应力条件对正确的确定劈裂注浆启劈压力至关重要,可为劈裂注浆的设计和施工会提供更加完善的理论依据。

地应力对地下洞室开挖的塑性区影响研究

结合河南宝泉抽水蓄能电站地下洞室开挖过程的三维非线性分析,讨论了地应力场中侧压力系数对围岩塑性区分布的影响。其中,岩体材料为理想塑性,屈服准则采用Drucker-Prager准则,从理论上推导了地应力中侧压力系统和材料参数与围岩塑性区之间的关系,主要是对洞室中典型的马蹄形洞室的3个最易出现塑性的区域进行了研究,得出了它们的塑性区分布规律与侧压力系数的关系。在河南宝泉抽水蓄能电站洞室开挖过程的三维非线性分析中,验证了这个规律。这些规律和认识可作为工程设计的参考和导则。

考虑裂尖塑性区影响的水力压裂缝高计算模型

为了对水力压裂裂缝高度进行准确预测,针对高应力多分层的复杂地层,基于断裂力学理论分析裂缝扩展过程中裂缝尖端应力集中产生的塑性区分布对缝高扩展的影响,建立水力压裂缝高计算模型并进行求解,通过与其他2种缝高模型(MFEH、FracPro)计算结果进行对比以验证该模型的准确性。模型实例计算的敏感性分析表明:水力压裂的缝高会呈现阶梯生长的扩展形态,且裂缝缝高越大,阶梯生长的现象越明显;地应力对裂缝缝高的生长起主要的控制作用,地层岩石断裂韧性只在一定程度上对缝高生长有抑制作用;压裂液密度的增大有利于裂缝下尖端的扩展。

任意截面无粘结预应力混凝土梁的极限非线性分析

在材料非线性应力-应变关系基础上,提出了确定任意截面无粘结预应力混凝土梁抗弯强度以及计算无粘结预应力筋极限应力的通用方法。利用修正的RODRIGUEZ截面模型进行截面强度分析,按截面顶点把截面划分为若干个梯形单元,通过对梯形单元积分求出混凝土内力。将极限状态下无粘结预应力梁等效塑性区长度与破坏截面中性轴高度之比看作一常数,通过对引自7个不同文献的140片无粘结预应力试验梁的非线性回归分析,认为这个常数取为9.78较为合理。计算结果与试验值吻合较好。

断层周围的弹塑性区及其地质意义

采用弹塑性有限单元方法 ,通过模拟符合实际状况的逐步加载过程所引起应力场和塑性形变区的研究 ,得出如下结果 :①在塑性或韧性剪切形变情况下 ,断裂或形变带的共轭剪切角往往大于 4 5° ;②在双向挤压应力条件下 ,先存断裂的前缘部位没有拉伸应力存在 ,但可能有伸展形变发生 ;③与最大主压应力夹角为 3 0°～ 90°的断层前缘是偏应力的优势方位 ,容易发生塑性剪切形变 ,特别是夹角为 60°左右的断层是最易发生新的构造活动的断层 ;④多数断层两侧一定范围内以及断层内部是相对的低应力区。这些应力的低值区 ,非常有利于矿液和油气的运移。

断续节理在Ⅱ型受载下的弹塑性分析

运用线场分析方法对岩体内的断续节理在面内剪切荷载作用下进行弹塑性分析，求得节理线附近塑性区应力场和节理线上塑性区长度随外载的变化规律。通过与试验结果的分析对比，计算结果与试验结果［１，２］有较好的一致性。

高强混凝土剪力墙抗震性能及其性能指标试验研究

为了改进高强混凝土(HSC)剪力墙的变形能力,按变形能力设计方法设计5个剪跨比分别为1.5和1.0的剪力墙试件,进行拟静力试验。根据试验结果,研究中高、低矮HSC剪力墙的破坏形态、破坏机理及变形性能。结果表明,分段约束箍筋对提高弯曲型剪力墙的变形能力是有效的;剪力墙变形能力设计方法在一定程度上是可靠的;剪力墙塑性铰区转角与其破坏程度有较好的相关性。根据墙体不同阶段的破坏程度,将剪力墙结构的性能划分为"使用良好、保证人身安全、防止倒塌"三个水平,提出用层间位移角和塑性铰区转角共同作为剪力墙结构的性能控制指标,并给出了三性能水平的建议值。将该HSC剪力墙与已有的普通混凝土剪力墙的试验结果进行比较,表明只要采取合理有效的抗震措施,并按强剪弱弯原则进行截面承载力设计,HSC剪力墙的抗震性能能满足设计要求。