Numerical Simulation of Dam-Break Flows Using Radial Basis Functions: Application to Urban Flood Inundation

Dam-break flows pose significant threats to urban areas due to their potential for causing rapid and extensive flooding. Traditional numerical methods for simulating these events struggle with complex urban landscapes. This paper presents an alternative approach using Radial Basis Functions to simulate dam-break flows and their impact on urban flood inundation. The proposed method adapts a new strategy based on Particle Swarm Optimization for variable shape parameter selection on meshfree formulation to enhance the numerical stability and convergence of the simulation. The method’s accuracy and efficiency are demonstrated through numerical experiments, including well-known partial and circular dam-break problems and an idealized city with a single building, highlighting its potential as a valuable tool for urban flood risk management.

Rock Breaking Performance of a Pick Assisted by High-pressure Water Jet under Different Configuration Modes

In the process of rock breaking, the conical pick bears great cutting force and wear, as a result, high-pressure water jet technology is used to assist with cutting. However, the effect of the water jet position has not been studied for rock breaking using a pick. Therefore, the models of rock breaking with different configuration modes of the water jet are established based on SPH combined with FEM. The effect of the water jet pressure, distance between the jet and the pick bit, and cutting depth on the rock breaking performance as well as a comparison of the tension and compression stress are studied via simulation; the simulation results are verified by experiments. The numerical and experimental results indicate that the decrease in the rates of the pick force obviously increases from 25 MPa to 40 MPa, but slowly after 40 MPa, and the optimal distance between the jet and the pick bit is 2 mm under the JFP and JSP modes. The JCP mode is proved the best, followed by the modes of JRP and JFP, and the worst mode is JSP. The decrease in the rates of the pick force of the JCP, JRP, JFP, and JSP modes are up to 30.96%, 28.96%, 33.46%, 28.17%, and 25.42%, respectively, in experiment. Moreover, the JSP mode can be regarded as a special JFP model when the distance between the pick-tip and the jet impact point is 0 mm. This paper has a dominant capability in introducing new numerical and experimental method for the study of rock breaking assisted by water jet and electing the best water jet position from four different configuration modes.

Experimental Study of Pore Water Pressure and Bed Profile Change Under Regular Breaking Waves

There lies a close relationship between the seabed destruction and the distribution of pore water pressure under the action of breaking wave. The experiments were carried out in a wave flume with a 1：30 sloping sandy seabed to study regular breaking wave induced pore water pressure. A wide range of measurements from the regular wave runs were reported, including time series of wave heights, pore pressures. The video records were analysed to measure the time development of the seabed form and the characteristics of the orbital motion of the sand in the wave breaking region. The pore water pressure in the breaker zone showed the time variation depending on the wave phases including wave breaking and bore propagation. The time-averaged pore water pressure was higher near the seabed surface. The peak values of pore water pressure increase significantly at the breaking point. The direction of pore water pressure difference forces in the breaker zone is of fundamental importance for a correct description of the sediment dynamics. The upwards- directed pressure differences may increase sand transport by reducing the effective weight of the sediment, thereby increasing the bed form evolution. The seabed configuration changed greatly at the wave breaking zone and a sand bar was generated remarkably. The amplitude of the pore water pressure changed with the seabed surface. The results are to improve the understanding of sand transport mechanisms and seabed responses due to breaking regular waves over a sloping sandy bed.

A method for detecting the breaking of wind-generated waves in deep water

The breaking of wind-generated waves is an important phenomenon in the ocean, having close relation to many aspects of the ocean, such as air-sea interaction, ocean wave dynamics, oceanic remote sensing and ocean engineering. The first problem encountered in both its theoretical study and practical measurement is how to detect the breaking of waves.

Analysis of Water Pipeline Breaks

This study explores the arrivals of water pipeline break failures. The aim is to assist the facility manager in the decision making process. Based on characteristics of the data set ranging from 2011 to 2014, two steps of analysis were presented in the paper. This first step is the analysis of partially complete data set (2011 data). The 2-sample KS test is adopted to check the similarity between this data set and the entire data set with no underlying distribution implied. In order to conduct the reliability analysis, the Weibull distribution is adopted to evaluate the data. For annual data set, the 2-parameter Weibull distribution fits data sets pretty well. The shape parameters are a little greater than 1, indicating a slightly increasing arrival rate of such failures. For the entire data set, the 3-parameter Weibull tends to fit the data better than the 2-parameter Weibull. The shape parameter is well above 1, indicating an increasing arrival rate of the failures. To eliminate the impact of missing points for the 2011 data set, data from 2012 to 2014 were also considered as a new set, the Weibull distribution generated a decent fitting. The shape parameter is a little greater than 1. Therefore, there is a slightly increasing arrival rate of those pipeline failures. Results from this study provide decision makers valuable information in terms of whether additional efforts shall be made to enhance the system’s performance in order to reduce the failure rate.

A Simulation Study of Support Break-Off and Water Inrush during Mining under the High Confined and Thick Unconsolidated Aquifer

The thick Cenozoic unconsolidated aquifer is deposited under Sunan syncline core in Huaibei coalfield, the water yield property of unconsolidated bottom aquifer is strong and water pressure is high in some areas (up to 4 MPa in some areas). Water inrush accident often occurs during mining under unconsolidated aquifer, the biggest characteristic is abnormal mine pressure and support break-off during water inrush accident comparing with normal condition. In order to study mechanism of?support break-off and water inrush during mining under the high confined thick unconsolidated aquifer, a simulation of similar material was designed. The experimental results indicated that, under normal condition, the compound breakage sequence of water-resisting key strata between coal seam and high confined thick unconsolidated aquifer is from top to bottom and the basic reason of synchronous fracture is the load of bottom key strata increased suddenly when the breakage of top key strata happened. Because of high confined thick unconsolidated aquifer, surface acts on the bottom key strata soil layer in the form of uniformly distributed load, which is the load-transfer mechanism of confined thick unconsolidated aquifer. Once the overlying key strata compound breaks, the height of unstable strata will reach far more than 30 meters and exceed support capability of current fully-mechanized mining supporter, which leads to support break-off accident during mining process under confined unconsolidated aquifer.

白云南洼珠海组陆架坡折带演化特征与深水沉积耦合关系

白云南洼珠海组沉积时期,盆地处于断陷向拗陷转化阶段,陆架坡折形态以及位置发生巨大变化,导致深水沉积的类型和特征具有明显差异。针对这种坡折演化对深水沉积类型的影响开展研究,通过对白云南洼珠海组三维地震剖面进行解译,识别珠海组各层段陆架坡折带,定量分析坡折特征及其演化规律,探讨坡折演化过程与深水沉积的耦合关系。研究结果表明,通过对珠海组沉积时期陆架坡折带定量分析,将其迁移演化类型划分为下降型、平直型、低角度上升型、高角度上升型4类;在井震结合的基础上,根据地震相组合以及沉积体系分布特点,识别出斜坡扇、块状搬运沉积、深水水道体、盆底扇4种主要的深水沉积类型;并发现陆架坡折演化类型与深水沉积类型存在明显的耦合关系:平直型、高角度上升型、低角度上升型和下降型陆架边缘迁移轨迹分别对应斜坡扇、块状搬运沉积、深水水道体和盆底扇的优势发育。此外,珠海组四段至珠海组三段陆架坡折带整体由下降型向低角度上升型转变,深水沉积体系以斜坡扇及深水水道体发育为主;珠海组三段至珠海组一段早期整体由低角度上升型向下降型转变,深水沉积体系以深水水道-盆底扇沉积体系为主;珠海组一段晚期整体由下降型向高角度上升型演化,深水沉积体系几乎不发育。本研究揭示了陆架坡折迁移对深水沉积体系类型和分布的控制作用,对深入理解深水沉积过程和油气勘探具有重要意义。

含磨料脉冲射流破岩效果试验研究

为探究脉冲磨料水射流的破岩效果,选用五种不同强度的硬岩,开展了脉冲纯水/磨料水射流破岩试验,并以冲蚀孔尺寸为指标,将脉冲纯水/磨料水射流的破岩效果同连续纯水/磨料水射流进行了对比。结果表明:连续磨料水射流冲蚀岩体过程主要依赖磨料粒子的磨削作用,而脉冲磨料水射流则是连续的水锤效应和磨料粒子磨削作用的叠加;无磨料粒子时,连续水射流破岩主要依赖射流初期的单个水锤效应,而脉冲水射流则是多个连续的水锤压力持续冲击岩石,导致岩体表面出现破碎区。

基于物质点法的深部煤层水射流破岩成孔机制和影响因素

我国深部煤层气资源丰富,但深部煤层渗透率极低,高应力−压力环境下深部煤层气解吸困难,导致产量低下。水平井水射流冲孔造穴是一种大范围卸压增透煤层的新技术,但在深部赋存环境下其破岩成孔机制还有待研究。由于深部煤层赋存于高地应力、高应力差的地质环境,室内物理模拟实验难以开展。因此,首先基于黏弹塑性理论和物质点法建立了水射流冲孔破岩数值模型,该模型集成拉格朗日和欧拉算法的优势,能有效模拟射流破岩过程中的动量交换、煤岩大变形、破岩、流体剥蚀携岩反排等全过程。然后,通过该数值模型开展了深部煤层水射流破岩成孔机制和影响因素研究,得到结论如下:①深部煤层以高地应力荷载作用造成的剪切破坏为破岩的主导机制,射流主要起到冲蚀和携岩反排的作用,而无应力荷载时以水射流碰撞煤岩产生的应力波造成张拉破坏为破岩的主导机制,由于煤岩塑性较强,水楔效应不明显。②深部煤层高地应力荷载作用加速了破岩过程,冲出煤量比无应力荷载时高,同时应力荷载促使煤体向开孔方向移动,造成空腔体积减小,但塑性损伤区较无应力荷载时明显增大。③冲出煤量、塑性损伤区面积都随射流时间增加而增加,但增幅逐渐变缓。冲出煤量、塑性损伤区面积随入射角度的增加整体呈下降趋势,射流角度越小,水射流冲孔破岩效果越好,射流垂直入射并不是破岩的最佳方式。④冲出煤量、塑性损伤区面积随应力差、煤岩开孔宽度的增加而增加,但应力差的增加对深部煤层射流破岩的促进作用不大。煤层开孔宽度不宜过高,适当增加开孔宽度可以提高射流破岩效率。

水击补气式压力罐及水力瞬变仿真

空气阀常常安装在输水管检修孔侧壁,进气后部分气体就会存留在检修孔上部产生气垫式压力罐的水击防护作用。据此,提出了水击补气式压力罐装置的设计方法,即利用泵站事故断电产生的水击负压现象,通过真空破坏阀或空气阀给压力罐补气,以防止输水管发生液体汽化现象并削减水击最大压力。然后,建立了水击补气式压力罐水力瞬变数值仿真数学模型。最后,以一个实际输水工程为例,计算比较了分别设置空气阀、空气阀调压室及真空破坏阀补气式压力罐时的水击防护效果,结果表明,补气式压力罐水击防护效果最好。

围压条件下粒子冲击破岩裂隙扩展机理研究

为揭示粒子冲击下围压对岩石裂隙形成及扩展机制的影响,开展了粒子冲击破岩试验和微纳米工业CT(compnted tomography)扫描试验,明确了围压对粒子冲击作用下岩石裂隙扩展特征的影响;并对不同围压条件下的粒子冲击进行数值模拟,分析了岩石的应力场和裂隙场演化过程,揭示了围压影响裂隙扩展的内在机制。结果表明,粒子冲击岩石后,在岩石内部形成破碎区和晶间主裂隙扩展区。压应力导致形成的剪切应力和拉应力是破碎区形成的主要原因,而晶间主裂隙扩展区形成的主要原因是切向衍生拉应力。围压使岩石颗粒间产生预应力,导致切向衍生拉应力需克服颗粒之间的初始压应力才能形成张拉裂隙;围压的增大导致岩石颗粒间剪切裂隙比例和摩擦效应提升,产生相同裂隙数目消耗能量增大,抑制了晶间主裂隙扩展区和破碎区的形成,破碎效果降低。

高压水射流辅助锥形PDC齿破碎花岗岩试验研究

深部地层岩石硬度高、研磨性强、可钻性差,地质条件复杂、施工难度大,高压水射流辅助钻井可有效延长钻头寿命,提高钻进效率。采用室内试验与理论分析相结合的方法,开展了高压水射流辅助锥形PDC齿破碎花岗岩试验,分析了高压水射流辅助锥形PDC齿和常规PDC齿破碎花岗岩特性,揭示了射流压力、喷射距离、喷嘴直径及喷射角度等因素对锥形PDC齿破岩效果的影响规律。研究结果表明:在高压水射流辅助破岩条件下,锥形PDC齿与常规PDC齿的破岩比能分别降低了17.36%与19.63%;射流压力越大,射流辅助锥形PDC齿破岩效果越好;在研究条件下,喷距范围为5~10 mm可使水射流辅助锥形PDC齿破岩效果最佳;当喷嘴直径为2 mm时,切削力离散系数最小;喷射角度为30°时,锥形PDC齿切削力与破岩比能达到最小值;喷射角度为20°时,切削力离散系数最小,切削力最稳定。研究结果可为适用于深部硬岩钻井的锥形PDC钻头水力结构设计与优化提供理论支撑。

基于响应面分析的淹没水射流破土施工参数优化设计

针对水射流破土过程中射流孔深度及径宽难以确定的问题,以圆柱形喷嘴为研究对象,基于拉格朗日-欧拉流固耦合算法建立了淹没水射流破土的有限元模型,并通过室内实验验证了该有限元模型计算结果的准确性。基于响应面法建立了射流孔深度与径宽的预测模型,分析了喷嘴直径、射流靶距和射流压力3个因素及其交互作用对射流孔深度及径宽的影响规律,结合满意度函数对破土施工参数进行优化。结果表明:当选取特定破土深度(10 cm、15 cm和20 cm)时,较大的射流压力(7.2 MPa)、较小的射流靶距(1 cm)及合适的喷嘴直径(0.928 mm、1.164 mm和1.345 mm)可最大程度地保证射流孔的稳定性。针对特定目标破土深度,优化后的射流孔深度及径宽的预测值与实验值的误差均小于15%,表明预测结果合理可靠。

水射流技术在海洋水合物钻采过程中的应用研究进展

天然气水合物是一种储量巨大、清洁高效的新型能源,我国海洋天然气水合物资源非常丰富,安全高效开采水合物能够助力实现我国能源结构转型与“双碳”战略目标。水合物储藏具有非成岩、弱胶结与温压敏感性强的特点,水射流技术应用于水合物钻采过程可有效解决常规方法引起的井壁坍塌与地层失稳等工程问题。本文总结了现有的水射流钻采水合物工艺与水射流钻具,分析了水射流冲击作用下含水合物沉积物破碎过程影响因素与破碎机理,最后对水射流技术在水合物钻采过程中的应用研究方向进行了展望,以期为我国海洋天然气水合物钻采技术研究提供参考。

基于高压水射流的钢筋混凝土破拆技术研究及应用

高压水射流技术的发展为钢筋混凝土建(构)筑物向绿色化拆除提供了新的技术保障。为了探究高压水射流技术在钢筋混凝土建(构)筑物拆除工程中的应用效果,采用理论分析、设计计算和室外试验,开展了基于高压水射流技术的钢筋混凝土结构体局部破拆模拟试验。试验结果表明:与传统机械破拆方法相比,高压水射流破拆效率提高50%以上,破碎程度高,破拆界面平整。同时,水射流破拆不会产生大量的粉尘,减少了对环境的污染,避免了碎石飞溅对作业人员的生命安全产生威胁。钢筋混凝土建(构)筑物高压水射流技术的应用可为国内外同类工程提供重要参考依据。

柔性环氧树脂材料性能研究

通过对环氧树脂材料中活性稀释剂、固化剂进行调配,提高环氧材料分子链中柔性成分的含量,从而改善固化后环氧树脂脆性大的问题。采用红外光谱、固结体力学性能、动态热机械法分析、断面形貌分析手段对材料由“脆”变“柔”进行了分析。结果表明,环氧树脂材料中主要是由于引入了醚基柔性基团,且随着固化剂含量增加,材料“脆”性得到改善。在试样EP-5时,具有最佳的“柔”性,此时断裂伸长率达到45%。动态热机械法分析数据表明试样EP-5有最低的玻璃化转变温度,EP-5试样断面形貌的“带状”数量最多且复杂,皆可反映出材料的“脆”性得到极大改善。

基于ALE算法的连续水射流破煤特征数值模拟研究

为了探究环境介质对水射流破煤特征的影响规律,采用ALE算法和LS-Dyna软件开展了连续水射流冲击破煤数值模拟研究,分析了淹没/非淹没环境下水射流传播特征、破煤特征,及两者破煤深度关系的时变特征。结果表明:由于水射流损耗较大,淹没环境下射流传播速度远小于非淹没状态下;淹没射流在环境介质的阻碍下发散导致破煤面积增大及深度降低,但损伤单元变化不大;淹没环境下开展破煤造穴时需要合理延长冲击时间或者缩小钻孔间距。

基于高压水射流破拆技术的混凝土界面质量分析

破拆处理是混凝土维修加固工程中不可缺少的一个环节,破拆界面的质量直接影响维修加固后的整体性和耐久性,采用不同破拆技术,混凝土处理界面的质量也差异较大。文中制备C40混凝土试块,分别采用机械和水射流技术对其界面进行破除。通过观察和计算,分析对比了破除界面的坚实度、裂纹分布、骨料暴露比和边缘完整性等质量指标,完善了质量对比的评价体系,验证了水射流破拆技术的优越性和应用前景。

聚合物水泥防水涂料耐水性能影响因素研究

研究了聚合物乳液种类、聚合物乳液Tg值、水泥用量、填料种类和硅烷偶联剂用量对Ⅱ型JS防水涂料浸水后拉伸强度保持率、断裂伸长率和吸水率等指标的影响,结果表明,随着浸水时间的延长,JS防水涂料的拉伸强度、断裂伸长率都有不同程度的下降;选用Tg值为-15.3℃的丁苯乳液,水泥用量为50%,填料选用重钙,适量添加硅烷偶联剂制得的JS防水涂料耐水性能较佳。

大社矿地面水射流径向水平破煤瓦斯治理技术研究

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