建筑结构控制爆破拆除的力学分析与应用

应用运动学、动力学理论建立建(构)筑物控爆坍落过程的力学模型,进而研究在非定常约束条件下坍落结构的力学特征。首次提出了采用延时起爆技术时,非自由质点系及其广义坐标应是建立在每一段位上的瞬间虚位移。在此基础上,分析求解运动过程中时控单元的质点自由度,为精确选定爆破部位及时序提供了设计理论和计算依据。同时,结合振动理论,将控爆时差、结构载荷分布调制为振动系统,形成坍落结构梁板单元的强迫振动,充分实现在运动中进一步解体、破碎其自身结构,并形成具有明显缓冲效果的下落过程。应用实践结果证明力学分析是正确的,为工程结构爆破拆除计算机辅助设计及动态模拟技术的有效应用奠定了基础。     

基于FLAC3D的破碎围岩巷道支护效果分析

为了解破碎围岩分别采用锚杆支护、锚喷支护以及锚喷+锚索耦合三种支护方式下的支护效果,进而为破碎围岩巷道选择合理的支护方式提供参考。通过借助FLAC^3D软件建立数值模型,分析不同支护条件下的破碎围岩巷道位移量、应力分布以及塑性区的时空演化特征。结果表明,采用锚喷+锚索耦合支护时,可以较好的控制巷道围岩的位移量、减小应力集中效应、缩小塑性区的影响范围。     

库水位变动下庄屋滑坡变形与稳定性分析

库水位变动是三峡库区滑坡等地质灾害频发的重要原因之一。为研究库水位变动对库岸涉水滑坡变形和稳定性的影响,以庄屋滑坡为例,结合GPS位移监测数据和数值模拟分析,探讨了该滑坡在库水升降过程中变形和稳定性的响应规律。结果表明,庄屋滑坡受库水影响滑坡后缘变形大于前缘,为推移式滑坡。水位变动过程中,滑坡渗流和稳定性变化具有动水压力型滑坡特点,即在水位上升时滑体内地下水浸润线呈内凹趋势,水位下降时滑体内地下水浸润线呈外凸趋势,且具有一定的滞后性;库水位上升时滑坡稳定性系数增大,水位下降时减小;当库水位保持在恒定水位时,稳定性系数也逐渐趋于稳定。     

基于修正幂律模型流体的柳叶形扶正器旋流规律及应用

为提高注水泥过程中水泥浆顶替效率，国内外愈来愈多地使用旋流扶正器。但是，目前旋流扶正器结构参数主要靠经验设计，缺乏理论基础也没有相关行业标准。针对依据文丘里效应设计的柳叶形旋流扶正器，基于修正幂律流体模型，构建了旋流扶正器旋流长度计算模型。通过数值模拟对旋流扶正器井下旋流规律进行研究，推导出了旋流扶正器在修正幂律流体条件下，周向平均速度和完全顶替的临界速度公式。基于旋流扶正器井下旋流规律，分析了井眼环空结构、流体性能、井下井壁附着力对水泥浆顶替效率的影响，优化了柳叶形旋流扶正器旋流角、扶正棱长度、扶正棱有效体积和扶正器高度等设计参数。对比分析了柳叶形与常规旋流扶正器在不同工况下的旋流长度，柳叶形扶正器的旋流长度比常规扇形平均提升了32%，比常规梯形扶正器平均提升了47%。柳叶形扶正器在新疆顺北油田顺北3井等20多井次超深井应用，应用井固井质量明显优于常规扇形的旋流扶正器。     

粉土界面恒刚度循环剪切试验研究

竖向循环荷载作用下桩土界面的作用机理是研究桩土摩擦疲劳的关键。针对循环荷载作用下桩-粉土界面的剪切性能,使用改进的剪切试验装置在恒刚度条件下进行循环剪切试验,研究循环次数、累积位移和法向刚度对其摩擦疲劳性能、循环后单调剪切性能的影响。试验结果表明,粉土在循环剪切过程中,法向应力和剪应力在初始10个循环内随循环数增加快速衰减,随着循环进行,逐渐趋于稳定;单次循环内在剪切位移方向变化时,土体呈现表现出剪缩-剪胀-剪缩交替现象,总体变形呈现剪缩的趋势;循环荷载作用下,粉土界面的法向应力和剪应力随法向刚度增大衰减速率增大,达到稳定的累积循环位移越小;粉土循环后的单调剪切、法向应力恢复的单调剪切的剪应力比小于首次单调剪切试验值,且法向应力恢复的循环后剪切试验的剪胀程度较小,表明循环剪切过程中界面处粉土颗粒棱角破碎,颗粒变得光滑。在对试验数据分析的基础上,提出了与累积位移、法向刚度和初始应力相关的无量纲累积位移,建立了法向应力和界面摩擦角随累积位移的衰减方程。     

Impact of Divalent Ions on Heavy Oil Recovery by in situ Emulsification

Many reservoir formation brines are characterized by high salinity and contain high concentrations of divalent ions such as calcium, magnesium, and potassium. These challenging conditions can render the surfactants ineffective during chemical flooding for enhanced heavy oil recovery. Various brine types can have an impact on the stability of emulsions generated with chemicals as chemicals have various resistant levels toward hard divalent ions and salinities. To investigate the impact of brine hardness on heavy oil-in-water emulsion stability, glass tube experiments, microscopic visualization and sandpack flooding experiments, and Hele-Shaw visualization experiments were conducted in this study under low-salinity/hard-brine, high-salinity/hard-brine conditions using commercial chemicals, which are designed for specific reservoir brine conditions. Recovery results demonstrated that complex colloidal solution introduced in the previous study with silica and Dodecyltrimethylammonium bromide (DTAB) along with screened chemicals from glass tube tests in this study can enhance heavy oil recovery significantly with an addition of low concentration of xanthan gum (Lee and Babadagli 2018). The results confirmed the robustness of the complex colloidal solution formula to enhance oil recovery with low concentration of polymer under any reservoir brine conditions. The study also demonstrates the potential of polymer as an emulsion stabilization additive for enhanced heavy oil recovery by in situ emulsion generation. Polymer effects seemed to be particularly dominant under the low-salinity conditions than high-salinity conditions.     

节理峰前剪切刚度软化模型及其影响因素分析

节理峰前剪切应力-位移曲线是研究节理剪切行为的重要内容。然而目前对于节理峰前剪切行为大多以线性描述,不能较好的描述非线性的特点。对于非线性的描述也仅仅是唯象描述剪切应力-位移曲线,未能反映影响模型的参数物理意义及影响因素。以峰前节理刚度软化行为为出发点,采用归一化的思想将节理剪切刚度与位移无量纲化,用双曲线函数表示出剪切刚度与位移之间的关系。提出了考虑刚度软化的峰前剪切本构关系,通过与试验结果对比验证了本构关系的合理性。影响该模型最重要的两个因素是初始剪切刚度与峰值剪切位移。以Greenwood和Williamson模型为基础在细观上探讨了初始剪切刚度的影响因素;抓住法向应力与节理粗糙度主要因素,探讨了影响峰值剪切位移的影响因素。对模型参数的研究有助于进一步阐明节理峰前剪切机理。     

复杂应力区段煤柱合理留设宽度仿真研究

针对南关煤矿3205运输巷道工作面掘进与支护困难、巷道变形严重且维修频繁的现状,为破解复杂应力情况下煤柱合理留设宽度这一关键性问题,借助FLAC 3D软件进行了应力场与位移场仿真分析。研究结果表明:显著的水平应力场、邻近的采动应力场与劣化的围岩稳定性三重因素的综合作用是制约3205运输巷正常掘进作业的瓶颈。在不同煤柱宽度方案比选过程中,窄煤柱在应对较强水平应力与剪切应力作用时处于劣势。煤柱宽度越大,采动应力场对煤柱及工作面的影响越小,采掘活动更为安全。经过方案比选,最终确立留设煤柱在复杂应力区段的合理宽度为30 m。     

Relating video game exposure,sensation seeking,aggression and socioeconomic factors to school performance

ABSTRACT

The time displacement hypothesis has been widely used to explain the effects of media use on academic performance. This approach has been criticised for its monocausality and weak explanatory power. Utilising a combination of different theoretical perspectives is better suited than utilising only one. Considering displacement, excitement, attraction and third variable hypothesis, this paper argues that the relation between video game use and school performance is not the same for all types of gamers by considering the influence of socioeconomic, psychological and contextual factors. It investigates how gaming patterns (frequency, time of day) and psychological characteristics (sensation seeking, aggression) are related to academic performance for primary and secondary school students. Five hundred and seven students from five primary and four secondary schools in Singapore participated in a paper-pencil survey. Results showed support for a combination of displacement and third variable hypothesis, as overall time spent on video games was negatively associated with primary school children’s and active gamers’ school performances. There was no significant relationship for secondary school children. For primary school children who play games in the morning and afternoon, video game use was negatively associated with school performance. There was no support for the attraction and excitement hypotheses.     

隧道洞口上方危岩崩塌块石运动规律及其对隧道的危害

为揭示危岩崩塌块石的运动规律及其对下方隧道洞口的危害,以都香高速昭通段乐红隧道洞口高陡边坡危岩区崩塌体为研究对象,运用理论计算与Rockfall数值计算2种形式对危岩区崩塌体失稳后块石的运动特征进行预测,运用Abaqus有限元软件模拟不同初速度、不同冲击落点下块石冲击隧道结构的动力响应,揭示不同因素对块石冲击隧道结构的影响程度.结果 显示:理论计算与Rockfall数值计算结果吻合,崩塌块石经坠落、碰撞、滚动最终会与隧道引洞段上表面发生碰撞;与冲击落点相比,块石初速度对隧道结构的动力响应特性影响更大;块石冲击落点位于隧道圆拱圆心正上方位置时对隧道结构的损伤最大;不同冲击落点对碰撞回弹后块石的速度影响不大.