RB-DEM Modeling and Simulation of Non-Persisting Rough Open Joints Based on the IFS-Enhanced Method

When the geological environment of rock masses is disturbed,numerous non-persisting open joints can appear within it.It is crucial to investigate the effect of open joints on the mechanical properties of rock mass.However,it has been challenging to generate realistic open joints in traditional experimental tests and numerical simulations.This paper presents a novel solution to solve the problem.By utilizing the stochastic distribution of joints and an enhanced-fractal interpolation system(IFS)method,rough curves with any orientation can be generated.The Douglas-Peucker algorithm is then applied to simplify these curves by removing unnecessary points while preserving their fundamental shape.Subsequently,open joints are created by connecting points that move to both sides of rough curves based on the aperture distribution.Mesh modeling is performed to construct the final mesh model.Finally,the RB-DEM method is applied to transform the mesh model into a discrete element model containing geometric information about these open joints.Furthermore,this study explores the impacts of rough open joint orientation,aperture,and number on rock fracture mechanics.This method provides a realistic and effective approach for modeling and simulating these non-persisting open joints.

Shear mechanical properties and energy evolution of rock-like samples containing multiple combinations of non-persistent joints

Discontinuities are often considered as important factors responsible for the instability caused by shear failure in engineering rock mass,and energy-driven instability is the root cause of rock failure.However,few studies focus on the energy evolution during the failure process using a three-dimensional(3D)numerical model.In this study,a series of laboratory direct shear tests on rock-like samples is numer-ically simulated using bonded particle models(BPMs)with multiple combinations of discontinuous in the particle flow code(PFC3D),in which the location and size of the particles conform to the uniform distribution.The effects of joint row number and inclination on the stress-strain characteristics and failure mode of rock were studied from the perspective of microcrack growth and energy evolution.The results showed that,when the number of joint rows Nr>1,the shear failure region does not change with the increase of Nr for the type B(2-columnn multiple-row at center)and the type C(2-column multiple-row at edge)as compared to the type A(1-column multiple-row at center)joint models.Notably,joints significantly increase the post-peak energy dissipation but have little effect on the proportion of energy before the peak.Friction consumes most of the energy while kinetic energy accounts for less than 1%of total energy during the shear process.Peak elastic strain energy follows the variation trend of peak shear displacement.The development and accumulation of microcracks directly affect the energy dissipation,and there is a significant linear relationship between the cumulative number of critical microcracks and the critical dissipated energy at the failure,when the dip direction of joints is opposite to the shear direction,more microcracks will be accumulated at the peak time,resulting in more energy dissipation.The results contribute to deeply understanding the shear failure process of non-persistent jointed mass.

Strength behaviour of a model rock intersected by non-persistent joint

Several constructions in the field of civil engineering quite often need to deal with rocks.Strength behaviour of rock intersected by a discontinuity or a set of discontinuities has been a topic of keen interest for engineering community.The popular attributes of discontinuities that have been given due importance are their frequency,orientation and surface characteristics.Non-persistency,however,has been given little attention.This article presents an experimental study wherein focus has been made on the effect of non-persistency of the joint on the uniaxial compressive strength(UCS)of a model rock for various geometries such as orientation,discontinuity length ratio and number of joint segments.The applicability of single plane of weakness theory(SPWT)to assess the strength of jointed specimens has also been evaluated.It has been noticed that SPWT captures the strength behaviour only for a narrow range of discontinuity orientations.As an improvement,an approach is suggested by extending concepts of degree of persistence and joint factor to have a better understanding towards strength behaviour of rocks intersected by non-persistent joints.

Failure behavior around a circular opening in a rock mass with non-persistent joints:A parallel-bond stress corrosion approach

The stability of underground excavations is influenced by discontinuities interspaced in surrounding rock masses as well as the stress condition. In this work, a numerical study was undertaken on the failure behavior around a circular opening in a rock mass having non-persistent open joints using PFC software package. A parallel-bond stress corrosion(PSC) approach was incorporated to drive the failure of rock mass around the circular opening, such that the whole progressive failure process after excavation was reproduced. Based on the determined micro parameters for intact material and joint segments, the failure process around the circular opening agrees very well with that obtained through laboratory experiment. A subsequent parametric study was then carried out to look into the influence of lateral pressure coefficient, joint dip angle and joint persistency on the failure pattern and crack evolution of the rock mass around the circular opening. Three failure patterns identified are step path failure, planar failure and rotation failure depending on the lateral pressure coefficient. Moreover, the increment of joint dip angle and joint persistency aggravates the rock mass failure around the opening. This study offers guideline on stability estimation of underground excavations.

Bearing capacity of foundations on rock slopes intersected by non-persistent discontinuity

Rocks encountered in foundations of heavy structures are invariably intersected by discontinuities(joints).In the past,several studies have been performed by researchers to incorporate the effect of fully persistent joints in the assessment of the load-carrying capacity of rocks.However,in the field,the joints are non-persistent,and an assumption of full persistency will underestimate the capacity.Recently,Shaunik&Singh have studied the influence of non-persistency,number of joint segments and discontinuity orientation on the strength behaviour of rock specimens(Shaunik and Singh,2019).Bell’s approach can be used to obtain the bearing capacity of shallow foundations placed in jointed rocks.In the present study,results of the experimental work(Shaunik and Singh,2019)conducted by Shaunik&Singh have been used to suggest expressions by extending Bell’s approach for computing bearing capacity of the foundation placed near the crown of a rock slope.Easy to use design charts are also presented for field application.Finally,a real-life problem from Indian Garhwal Himalayas is considered,and the approach suggested in this study is utilised to obtain the bearing capacity of a bridge foundation as a function of uniaxial compressive strength(UCS)of intact rock,joint friction,spacing and orientation of joint,nonpersistency and number of joint segments.

基于表层温度深度学习的电缆接头绝缘劣化非接触式诊断

为提升电缆中间接头绝缘层劣化程度的现场诊断效率和准确度,提出一种基于表层温度自适应深度学习的接头绝缘劣化状态非接触式诊断方法。首先,对电缆接头及两端电缆的绝缘表层进行红外热成像,实现电缆接头中心两边多个对称区域的表层温度、接头两端电缆的表层温度的非接触式采集;其次,构建基于双隐层自编码极限学习机的深度学习网络,以挖掘表层温度数据内部深层次隐含特征,将提取的深度隐含特征作为随机森林诊断模型输入;然后,提出一种非线性动态自适应旋转角的量子旋转门以改进量子烟花算法的更新策略,并用于诊断模型参数优化;最后,结合接头表层红外温度和绝缘介质损耗角正切值构建数据集,对诊断模型进行训练和现场测试。实验结果表明,改进后的量子烟花算法可以较好地逼近全局最优解、收敛效率高,深度学习随机森林诊断模型具有较强的特征抽取和分类能力,参数优化后诊断模型的分类精度和稳定性得到有效提高,在小样本训练集条件下就能达到较好的诊断效果,可实现接头绝缘劣化状态的非接触式诊断。

FPSO串靠外输作业溢油风险分析及应对措施

深入研究浮式生产储卸油装置(FPSO)串靠外输作业溢油风险问题,通过归纳、总结FPSO串靠外输作业的特点和溢油原因及可能导致的环境和经济影响,提出一系列应对措施,包括加强天气的预测及前期准备工作、设备定期检查和隐患整改、人员技能提高、各项安全制度的贯彻执行等,从而有效降低FPSO串靠外输作业溢油风险,保护海洋生态环境,保障经济利益,也可为相关领域的研究提供借鉴。

Influence of degree of interlock on confined strength of jointed hard rock masses

The strength of jointed rock mass is strongly controlled by the degree of interlock between its constituent rock blocks.The degree of interlock constrains the kinematic freedom of individual rock blocks to rotate and slide along the block forming joints.The HoekeBrown(HB)failure criterion and the geological strength index(GSI)were developed based on experiences from mine slopes and tunneling projects in moderately to poorly interlocked jointed rock masses.It has since then been demonstrated that the approach to estimate the HB strength parameters based on the GSI strength scaling equations(called the‘GSI strength equations’)tends to underestimate the confined peak strength of highly interlocked jointed rock masses(i.e.GSI>65),where the rock mass is often non-persistently jointed,and the intact rock blocks are strong and brittle.The estimation of the confined strength of such rock masses is relevant when designing mine pillars and abutments at great depths,where the confining pressure is high enough to prevent block rotation and free sliding on block boundaries.In this article,a grain-based distinct element modeling approach is used to simulate jointed rock masses of various degrees of interlock and to investigate the influences of block shape,joint persistence and joint surface condition on the confined peak strengths.The focus is on non-persistently jointed and blocky(persistently jointed)rock masses,consisting of hard and homogeneous rock blocks devoid of any strength degrading defects such as veins.The results from this investigation confirm that the GSI strength equations underestimate the confined strength of highly interlocked and non-persistently jointed rock masses.Moreover,the GSI strength equations are found to be valid to estimate the confined strength of persistently jointed rock masses with smooth and non-dilatant joint surfaces.

止血带对类风湿关节炎患者全膝关节置换围术期失血量的影响

背景:不使用止血带行全膝关节置换可以减少围术期总失血量。而诊断为类风湿关节炎的患者在行全膝关节置换术中不使用止血带会影响围术期出血量,尤其是隐性失血。目的:探讨止血带对类风湿关节炎患者在全膝关节置换围术期失血量的影响。方法:回顾分析2016年1月至2021年12月在上海市光华中西医结合医院关节外科行单侧全膝关节置换的类风湿关节炎患者80例作为研究对象,所有患者均在全麻下行全膝关节置换,试验组39例患者全程不使用止血带,对照组41例患者全程使用止血带。记录并比较两组患者总失血量、术中出血量、显性失血量、隐性失血量、隐性失血百分比、术后输血率、手术时间、术后3 d膝关节肿胀度、术后换药次数及切口延迟愈合率。结果与结论:①试验组术后隐性失血百分比均低于对照组,差异有显著性意义(P<0.05);试验组术中出血量、手术时间均大于对照组,差异有显著性意义(P<0.05);两组围术期总失血量、隐性失血量、显性失血量、输血率比较,差异均无显著性意义(P>0.05);②试验组术后3 d膝关节肿胀度小于对照组,差异有显著性意义(P<0.05);两组术后换药次数、切口延迟愈合例数相比差异均无显著性意义(P>0.05);③提示类风湿关节炎患者在全膝关节置换过程中全程不使用止血带,不会增加围术期总失血量、隐性失血量,且可以减少术后肢体肿胀的发生。

化瘀止血方对初次人工全膝关节置换术隐性失血与术后膝关节功能恢复的影响

【目的】观察化瘀止血方对中晚期膝骨性关节炎(KOA)患者初次人工全膝关节置换(TKA)术后隐性失血及膝关节功能康复的影响。【方法】将98例中晚期KOA拟行单侧TKA治疗的患者随机分为中药联合组和对照组,每组各49例。2组患者均予以TKA治疗,对照组给予围术期常规使用氨甲环酸和术后常规西药治疗,中药联合组在对照组的基础上,于术后第1天开始给予口服化瘀止血方治疗,疗程为14 d,并给予3个月以上的随访。观察2组患者术前、术后血红蛋白、红细胞计数、膝关节美国特种外科医院(HSS)评分的变化情况,比较2组患者术后血虚症状积分、凝血功能以及术后并发症的差异。【结果】(1)研究过程中,有3例患者失访,最后共有95例患者完成随访,其中对照组为48例,中药联合组为47例,平均随访时间为(1.50±0.23)年。(2)与对照组相比,中药联合组患者在术后1周的平均血红蛋白和红细胞计数均明显升高(P<0.05或P<0.01),且中药联合组在术后1周的平均血虚症状积分明显低于对照组(P<0.01)。(3)与对照组相比,中药联合组在术后1周的平均凝血酶原时间明显延长(P<0.01),平均D-二聚体水平明显降低(P<0.01),但2组患者在术后1周的部分凝血活酶时间比较,差异无统计学意义(P>0.05)。(4)术后1个月和3个月,2组患者的膝关节HSS评分均明显高于术前(P<0.05),术后3个月,2组患者的膝关节HSS评分又均明显高于术后1个月(P<0.05);组间比较,中药联合组在术后1个月和3个月的膝关节HSS评分均明显高于对照组(P<0.01)。(5)中药联合组的术后并发症发生率为2.13%(1/47),明显低于对照组的14.58%(7/48),组间比较,差异有统计学意义(P<0.05)。【结论】化瘀止血方能显著升高初次TKA术后短期血红蛋白及红细胞水平,促进凝血功能恢复,改善患者的整体血虚症状,减少术后隐性失血量,促进术口愈合以及膝关节功能康复,降低术后并发症的发生风险。

基于多重联合概率与改进加权HMM的风电功率预测方法

为解决传统风电功率预测中气象因素与功率数据结合应用时相互约束性不足且风电功率序列的历史时序信息随时间逐步衰减的问题,提出一种基于多重联合概率与改进加权隐马尔可夫模型(HMM)的风电功率预测方法。首先,提出多重联合概率方法将数值天气预报(NWP)中的气象因素进行逐步联合,并改进HMM中的释放概率,使NWP气象数据与功率时间序列融合以互相约束;然后,采用条件熵改进粗糙集以计算多步预测的合理属性权重,加权运算多步预测值,以获得风电功率预测值;最后,经过风电场实际算例验证,通过将NWP数据与功率数据相互融合、互相约束,可有效地提高风电功率预测精度。

Gut Microbes’Fatty Acid Gifts Enable Specialized Immune Defenders

Our trillions of gut microbes aren’t just along for the ride–they actively shape our health in unseen ways.Now,a research team,jointly led by Dr.SONG Xinyang from the Shanghai Institute of Biochemistry and Cell Biology(SIBCB)of the Chinese Academy of Sciences and Dr.Dennis L.Kasper from the Harvard Medical School,illuminates a hidden immune pathway sparked by bacterial fatty acids.

隐性失血对双侧人工全膝关节同期置换手术的影响

[目的]研究双侧人工全膝关节同期置换术术后隐性失血的相关因素。[方法]对2005年2月～2007年2月44例双侧人工全膝关节同期置换术患者进行回顾性分析,通过Gross方程,根据身高、体重及手术前后的红细胞压积推算术后平均显性失血量及平均隐性失血量。[结果]平均总失血量2065ml,其中显性失血量1198ml,隐性失血量867ml,使用自体血回输患者总失血量为2180ml,隐性失血量为937ml(42%);未使用自体血回输患者的总失血量是1950ml,隐性失血量是799ml(41%);两组的隐性失血相比差异无统计学意义。[结论]双侧人工全膝关节同期置换术术后隐性失血量占总失血量的比例较高,且使用自体血回输不能完全满足机体恢复体循环的需要,在围手术期要特别注意及时补充血容量。

柱状节理玄武岩隧洞破坏模式及其力学机制模拟

柱状节理岩体由于其内部赋存大量的隐节理面,开挖卸荷后极易出现隐节理面开裂松弛等特征,导致其破坏模式异于一般岩体。其破坏模式主要受到异常发育的节理面和较高地应力的共同作用影响。由于柱状节理岩体节理面发育,岩体结构控制型破坏占主要部分,包括单临空面节理面滑移(塌方)、多临空面节理面滑移(塌方)、与错动带、断层等弱面相组合的坍塌等破坏模式;应力控制型破坏主要为河谷侧顶拱喷层开裂;应力-结构面型破坏主要为岩性交界处的节理岩体塌落等。柱状节理岩体表层主要发生柱内竖直隐节理面和柱间节理面的拉破坏,而围岩内部的柱状节理主要发生柱间节理面的剪切破坏。因此,现场柱状节理的支护也应主要包括两个方面:以喷射混凝土钢纤维来阻止柱状节理岩体表层的张性开裂,以系统锚杆来控制柱状节理岩体内部的剪切破坏。

基于双正交法的焊缝早期隐性损伤临界状态磁记忆特征

针对焊缝早期隐性损伤临界状态磁记忆特征提取及评价难题,在大量试验基础上提出双正交法:即焊缝检测路径的正交性和磁场矢量分析的正交性。以Q235B焊接试件为试验材料,通过测量焊缝纵向和横向磁记忆信号分布,引入磁场正交矢量空间图和李萨如图,研究疲劳载荷下焊缝隐性损伤演化的磁记忆表征规律,对比扫描电镜和X射线检测结果,获得焊缝早期隐性损伤临界状态磁记忆特征:隐性损伤出现时李萨如图会产生涡动性的局部闭合,随着损伤的扩展涡动性局部闭合的面积越来越大直至断裂时完全闭合。在此基础上提出正交矢量梯度积分S(K)和正交矢量合成梯度比Kr的概念,建立Kr与剩余寿命Nr定量关系模型,为焊缝早期隐性损伤临界状态的定量研究提供一种新的思路。

膝骨性关节炎分级与全膝关节置换后隐性失血

背景:人工膝关节置换的对象群体年龄偏高,常伴有高血压病、糖尿病等基础性疾病,身体条件较差,所以围置换期失血成为影响置换安全的重要影响因素。目的:分析初次行人工膝关节置换围置换期的隐性失血量,以及根据膝骨性关节炎严重程度对围置换期出血量进行置换前评估的方法。方法:对行人工膝关节置换的膝骨性关节炎患者126例进行回顾性分析,根据Kellgren和Lawrecne影像学分级把患者分为Ⅲ级组与Ⅳ级组,对两组患者的隐性失血量进行统计学分析。结果与结论:纳入患者平均总失血量1560mL,其中隐性失血量865mL(55%),Ⅲ级组平均总失血量1290mL,其中隐性失血量684mL(占总失血量53%),Ⅳ级组平均总失血量1644mL,其中隐性失血量921mL(占总失血量56%),对两组数据进行统计学分析比较,在平均总失血量与隐性失血量上差异有显著性意义(P<0.05),而在隐性失血所占比例上差异无显著性意义。结果提示膝骨性关节炎影像学分级等级越高,人工全膝关节置换围置换期平均总失血量和隐性失血量越大,而隐性失血的比例变化不明显。对不同严重程度的膝骨性关节炎患者进行关节置换前出血量预测评估,对加强患者围置换期血液管理及保证患者生命安全有积极意义。

人工关节置换术后失血的相关研究

人工全髋关节置换术(total hip arthroplasty,THA)和人工全膝关节置换术(total knee arthroplasty,TKA)的患者在术后常存在严重的隐性失血,通常导致患者下床行走的时间推迟,功能恢复缓慢,严重影响临床疗效。隐性失血量可以根据Gross方程来计算,虽然在髋、膝关节置换术后预防贫血减少异体输血量的治疗方面已经取得了很多经验,但隐性失血的真实机制尚未明确。对隐性失血机制的正确研究有助于提高临床评估能力,可帮助关节置换患者顺利度过围手术期,有利于术后早期开展关节功能锻炼。文中就人工关节置换术后的隐性失血的机制及治疗方面进行分析,为今后的临床治疗及研究奠定基础。

黄土地区公路暗穴顶板临界厚度的确定方法

针对西部黄土地区暗穴的发育会对公路路基、桥涵、公路隧道、路堑与路堤边坡及边坡支挡工程等的稳定性造成严重威胁的问题,在野外调查的基础上,对暗穴的分布规律、发育形态、破坏机制等进行了归纳与研究,提炼出几种破坏模式,结合黄土地区的土质特点,考虑了节理对黄土暗穴的影响,采用结构力学等方法,提出了一些确定顶板临界厚度的方法,并进行了对比讨论。通过对路基暗穴的安全厚度的正确估算,为研究公路暗穴有效防治措施提供了可靠的依据。

静脉应用氨甲环酸对初次全膝关节置换术后失血与关节肿胀程度的影响

目的:研究氨甲环酸对初次人工全膝关节置换术(total knee arthroplasty,TKA)术后失血和膝关节肿胀程度的影响。方法:将行初次全膝关节置换术的60例膝关节骨性关节炎患者随机分为2组,氨甲环酸组30例在松止血带前静脉滴注氨甲环酸(15 mg/kg),对照组30例给予等量生理盐水静脉滴注。比较两组显性失血量、隐性失血量、输血率、术后D-二聚体、C反应蛋白以及关节肿胀程度,并观察术后是否出现下肢深静脉血栓等围术期并发症。结果:氨甲环酸组显性失血量、隐性失血量、输血率、术后C反应蛋白浓度均明显低于对照组(P<0.05)。氨甲环酸组在术后1周及2周髌上周径和腓肠肌周径均明显小于对照组(P<0.05)。两组患者术后D-二聚体差异无统计学意义(P>0.05),且均未出现下肢静脉血栓及肺栓塞的临床表现。结论:静脉应用氨甲环酸可以明显减少初次人工全膝关节置换术的显性及隐性失血量,降低输血率,同时可以减轻患肢关节的术后肿胀程度,并且不增加静脉血栓栓塞的风险,有利于患者术后早期康复。

全膝关节置换静脉滴注氨甲环酸联合含氨甲环酸鸡尾酒局部应用的止血效果及安全性

背景:膝关节置换围术期出血较大,含有氨甲环酸的"鸡尾酒"有止血和镇痛的双重作用,然而如何联合静脉使用氨甲环酸进一步减少出血仍值得探讨。目的:在使用含氨甲环酸的"鸡尾酒"前提下,对比联合不同方式静脉使用氨甲环酸在全膝关节置换术中的止血效果和安全性。方法:回顾性分析2017年6月至2019年9月中山市人民医院骨一科收治行初次单侧全膝关节置换膝骨关节炎62例患者的病历资料,分成3组,其中A组26例术中关闭切口前局部给予含有氨甲环酸的"鸡尾酒";B组25例在A组基础上术前切皮前静脉点滴1.0 g氨甲环酸;C组11例在B组基础上于术后3 h再次静滴1次1.0 g氨甲环酸,对比分析3组患者显性、隐性及总失血量、术后血红蛋白最大丢失量、输血率、术后住院时间、术后并发症等。结果与结论:①在总失血量、隐性失血量、术中出血量、术后引流量、显性失血量、血红蛋白最大丢失量方面,B、C组均低于A组,差异有显著性意义(P<0.05);B组与C组间比较差异无显著性意义(P>0.05);②输血率和术后住院时间,3组间差异无显著性意义(P>0.05);③3组在伤口并发症、关节腔积液、肌间静脉血栓并发症发生率方面,差异均无显著性意义(P>0.05),且3组均未发现下肢深静脉血栓形成及肺动脉栓塞;④结果表明,在全膝关节置换手术切皮前静脉使用1次1.0 g氨甲环酸以及联合含0.5 g氨甲环酸的"鸡尾酒"具有明显的止血效果,但是术后3 h再次静脉使用1次1.0 g氨甲环酸未能进一步减少出血;而且前两者均不增加术后并发症,有一定的安全性。