Semi-solid Casting of High Speed Steel Ingots Using Inclined Slope Pre-crystallization Method

Semi-solid casting of M2 high speed steel ingots was investigated by inclined slope pre-crystallization method. Effects of casting temperature and slope length on the microstructure of M2 HSS ingots were investigated. M2 cast ingots of non-dendritic primary austenite and fine eutectic ledeburite network carbide structure were obtained, with the casting temperature, slope length and angle of 1480 ℃, 500 mm and 60° respectively. Meanwhile, the microstructure of cast samples was quantitatively assessed by Image tool software. Results show that optimum mean equivalent diameter of primary austenite crystal grain is 50.8 μm, shape factor is 0.83, and mean thickness of network carbide is 5.21 μm.

Hydrodynamic characteristics and particle tracking of 90° lateral intakes at an inclined river slope

Lateral intakes are common in rivers.The pump effciency and sediment deposition are determined by the local hydrodynamic characteristics and mainstream division width.The hydraulic characteristics of lateral withdrawal from inclined river slopes at different intake elevations should be investigated.Meanwhile,the division width exhibits significant vertical non-uniformity at an inclined river slope,which should be clarified.Hence,a three-dimensional(3-D)hydrodynamic and particle-tracking model was developed with the Open Source Field Operation and Manipulation(Open FOAM),and the model was validated with physical model tests for 90°lateral withdrawal from an inclined side bank.The flow fields,withdrawal sources,and division widths were investigated with different intake bottom elevations,withdrawal discharges,and main channel velocities.This study showed that under inclined side bank conditions,water entered the intake at an oblique angle,causing significant 3-D spiral flows in the intake rather than two-dimensional closed recirculation.A lower withdrawal discharge,a lower bottom elevation of the intake,or a higher main channel velocity could further strengthen this phenomenon.The average division width and turbulent kinetic energy were smaller under inclined side bank conditions than under vertical bank conditions.With a low intake bottom elevation,a low withdrawal discharge,or a high main channel velocity,the sources of lateral withdrawal were in similar ranges near the local inclined bank in the vertical direction.Under inclined slope conditions,sediment deposition near the intake entrance could be reduced,compared to that under vertical slope conditions.The results provide hydrodynamic and sediment references for engineering designs for natural rivers with inclined terrains.

Exploring mechanism of hidden,steep obliquely inclined bedding landslides using a 3DEC model:A case study of the Shanyang landslide in Shaanxi Province,China

Catastrophic geological disasters frequently occur on slopes with obliquely inclined bedding structures(also referred to as obliquely inclined bedding slopes),where the apparent dip sliding is not readily visible.This phenomenon has become a focal point in landslide research.Yet,there is a lack of studies on the failure modes and mechanisms of hidden,steep obliquely inclined bedding slopes.This study investigated the Shanyang landslide in Shaanxi Province,China.Using field investigations,laboratory tests of geotechnical parameters,and the 3DEC software,this study developed a numerical model of the landslide to analyze the failure process of such slopes.The findings indicate that the Shanyang landslide primarily crept along a weak interlayer under the action of gravity.The landslide,initially following a dip angle with the support of a stable inclined rock mass,shifted direction under the influence of argillization in the weak interlayer,moving towards the apparent dip angle.The slide resistance effect of the karstic dissolution zone was increasingly significant during this process,with lateral friction being the primary resistance force.A reduction in the lateral friction due to karstic dissolution made the apparent dip sliding characteristics of the Shanyang landslide more pronounced.Notably,deformations such as bending and uplift at the slope’s foot suggest that the main slide resistance shifts from lateral friction within the karstic dissolution zone to the slope foot’s resistance force,leading to the eventual buckling failure of the landslide.This study unveils a novel failure mode of apparent dip creep-buckling in the Shanyang landslide,highlighting the critical role of lateral friction from the karstic dissolution zone in its failure mechanism.These insights offer a valuable reference for mitigating risks and preventing disasters related to obliquely inclined bedding landslides.

Effect of the inclined weak interlayers on the rainfall response of a bedded rock slope

Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geomechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG(Fiber Bragg Grating) sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from thesuperficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon 0.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.

高海拔铁路隧道斜井机械化配套与快速施工

为解决高海拔高寒地区斜井施工存在气压低、含氧量低、温差大、严寒干燥等问题,以某高海拔铁路隧道斜井工程为背景,结合围岩等级、断面大小、海拔高度,根据斜井施工机械化配套原则,提出高海拔陡坡长斜井机械化安全快速进洞施工工法,并选配超前支护、钻爆、装运、喷锚支护、衬砌等机械化作业线的成套设备。基于高度机械化的设备配套,提出“快挖、快运、快支”的高效施工技术以及各工序快速衔接工艺。以控制围岩变形为核心,构建一套积极干预加固围岩、注重早期支护并快速闭合的主动支护体系。结果表明:与普通钻爆法施工相比,采用三臂凿岩台车高度机械化配套施工效率高,月最快进尺为180 m,较人工钻爆法施工月进尺为130 m相比提高了近30%,施工质量稳定,作业人员投入少,且拱顶沉降和周边收敛均小于规范要求值,衬砌强度可靠,可实现高海拔小断面隧道“快挖、快支、主动支、快封闭”。

青藏高原多年冻土区单桩受斜坡地基土原位冻胀影响下的力学特性研究

在青藏高原多年冻土区铁路建设中,由于高原山区地形地貌复杂,建设在斜坡中的桩基础不在少数,地基土经历冻融过程以后桩基常常发生倾斜,严重影响铁路运行安全。为揭示在地基冻胀影响下多年冻土区斜坡单桩的倾斜机理,基于传热学与弹性力学,建立桩体体系热力耦合计算模型并进行室内试验验证计算模型的合理性,考虑地基土原位冻胀、水分相变、大气变暖等因素,进行地基土冻胀影响下斜坡桩基力学特性模拟分析。研究表明:斜坡桩体在地基土冻胀过程受到不均匀水平冻胀力、产生水平位移以及桩体弯矩,且水平位移随着地基斜坡坡度增大而增大;因不均匀水平冻胀引起的桩体应力占总应力的46.3%,对桩体安全性以及工程寿命产生较大影响。进行受到斜坡地基土冻胀影响下单桩力学特性分析,揭示在地基冻胀影响下多年冻土区斜坡单桩的倾斜机理,对多年冻土区斜坡桩基设计及运营有一定的参考价值。

岩石结构面Grasselli二维粗糙度指标优化及其JRC估算

采用只考虑迎剪侧表观倾角而忽略内部起伏角的Grasselli二维形貌参数θ_(G)来估算结构面粗糙度系数JRC仍有待改进。从θ_(G)的物理意义出发,发现爬坡区内部凸起高度对粗糙度的贡献可表示为其在总爬坡水平距离上的坡角,所有爬坡区提供的坡角之和定义为结构面内部起伏体粗糙贡献,将结构面迎剪侧表观平均倾角θ_(G)和爬坡区内部平均坡角θ_(H)叠加,提出岩石结构面粗糙度新指标θ_(C)。通过获取十条标准JRC剖面线的θ_(C),分析其与JRC之间的关系,建立基于θ_(C)的JRC估算式。计算不同采样间距和不同采样方向下的新指标θ_(C),结果显示θ_(C)具有分形特征且能够反映结构面形貌各向异性。进一步将JRC估算式应用于JRC-JCS模型,通过对比已有研究得到的试验结果以及不同抗剪强度模型的预测效果,验证基于新指标θ_(C)估算的JRC可以准确预测结构面峰值抗剪强度。最后,对二维指标θ_(C)进行三维拓展,提出三维粗糙度新指标(θ_(C))_(3D),并通过结构面形貌各向异性表征验证了其合理性。

单排微型桩加固缓倾长大裂隙土边坡的力学机制

预制混凝土微型桩广泛应用于南水北调工程含长大裂隙膨胀土边坡抢险加固工程,研究其加固力学机制,对膨胀土边坡安全防护具有重要意义。在相似模型试验的基础上,建立含裂隙面边坡滑体及微型单排桩模型;以平行裂隙面方向施加推阻力,开展了相似模型试验及数值模拟。结果表明:微型单排桩加固表现出较好的阻滑效果,将坡体系统的抗滑力维持在较高水平,边坡抵抗破坏的韧性增加,边坡稳定性显著提高。边坡抗滑阻力随桩间距增加而减小,单根微型桩的影响范围有限,随着桩间距的增大,土拱效应逐渐减弱,当桩间距为12倍桩直径时,桩之间的相互作用可以忽略,建议桩间距取8倍桩直径;布置在边坡中部的微型桩加固效果较布置在边坡上1/3位置的微型桩加固效果更好。

基于离散元法的反倾边坡动力破坏模式及分区研究

在地震作用下,一旦诱发反倾路堑边坡的失稳破坏,将对高速公路的安全运行带来不可估量的损失。为研究反倾边坡的动力响应特征,利用UDEC离散元软件模拟了Scavia反倾边坡模型在双向地震作用下的位移过程,分析了块体的运动模式。结果表明:在双向地震作用下,反倾边坡各岩块从稳定状态到滑出坡体的运动状态是相互转换的,靠近坡体后缘岩块运动状态的相互转换更为剧烈;根据块体的运动状态,可以分为3个区域,其中位于坡体前端的岩块主要经历“滑动—倾倒—滑动-倾倒”的状态变化,坡体中部则在滑动-倾倒与滑动状态之间相互转换,且转换速度慢,而坡体后缘岩块运动模式为“滑动—倾倒—滑动-倾倒—滑动”状态,其中滑动-倾倒状态到滑动状态相互转换,且转换速度快。

基于FLAC3D软件的岩质边坡稳定性分析方法研究

山地丘陵地貌中普遍分布岩质边坡,此类边坡存在严重滑坡隐患,因此本文基于FLAC3D软件研究岩质边坡的稳定性。以金属开采矿区为研究对象,获取基本工程概况与边坡参数,并分析滑坡基本概念。利用混合离散技术与拉格朗日差分法求解FLAC3D软件运动方程,构建研究区域边坡稳定性模型,通过仿真计算分析岩质边坡稳定性。实验结果表明:该研究区域整体稳定性较好,仅边坡上部被结构面控制的区域应力与位移较大,存在安全隐患;弱面倾角比坡脚倾斜度更大时,顺倾向边坡的稳定性更高;坡脚倾斜度越大,岩质边坡的稳定性越差。

降雨作用下倾斜层理岩质边坡稳定性数值模拟分析

为研究倾斜层理的岩质边坡在降雨条件下的稳定性情况,结合云南普朗铜矿重点地质灾害协同演变及智能监测预警系统关键技术研究工程实践,选取普朗地区一处具有代表性的边坡,采用数值模拟软件进行单项流固耦合分析,从边坡的含水率、坡体位移和安全系数等方面,进行不同层理倾角的边坡稳定性分析。研究结果表明坡体处于稳定状态,层理倾角的大小会对边坡的稳定性产生影响,层理倾角为75°时,坡体的最大位移量最小,安全系数最大。

缓倾软弱夹层对顺层岩质边坡稳定性的影响

为详细了解缓倾软弱夹层对顺层边坡稳定性的影响,以广西六宾高速K23+350~K23+550右侧挖方边坡为例,采用理论计算和数值模拟的方法开展软弱夹层对上覆弃渣体顺层岩质边坡稳定性影响的研究。研究结果表明,在最不利工况下软弱结构面处的位移相对较小,岩质顺层边坡处于稳定状态。弃渣体堆载体部分在暴雨工况下安全系数不满足规范要求,需对其进行加固。

含缓倾结构面的岩质桥址边坡地震稳定性评价及加固优化

桥址边坡地震稳定性评价在桥梁建设中十分重要,山区岩质桥梁桥址边坡稳定性多受结构面控制.文中依托某公路桥梁典型桥址边坡,利用有限元数值模拟技术,考虑了岩土材料应变软化特性,研究了含缓倾软弱结构面桥址边坡地震作用下安全稳定性.结果表明:考虑岩土材料应变软化的有限元数值仿真技术能较好地揭示含缓倾结构面的桥址边坡的多级潜在滑动特征.地震荷载作用加剧了坡内多级滑面的渐进发展趋势,多级滑面发育的时空顺序为:一级主滑面-二级主滑面-次级滑面,安全设计需要依据墩台部位的上下边坡地震工况下的稳定性进行.根据该桥主墩位置上下边坡地震的稳定性和变形特征,提出了针对缓倾结构面注浆加固和预应力锚索联合加固优化方案.

高铁隧道进口斜井反坡排水施工方案与管控

为有效消除水害对隧道施工的安全威胁,必须采取合理有效的施工技术。该文以某高铁富水隧道为例,结合其水文地质条件复杂、涌水量大等情况,制定相应的斜井反坡排水施工方案,根据总体方案确定科学合理的设备选型和排水系统构建,并提出相应的排水管理和方案实施管控措施,确保隧道施工安全。该文旨在为类似隧道施工提供参考。

急倾斜煤层回采参数研究

近年来由于煤炭资源的不断开采,矿井深度增加导致煤层地质条件不断恶化,尤其是急倾斜煤层的回采工作,对开采工艺有着极高的要求。结合当前急倾斜煤层开采工艺现状,通过分析急倾斜煤层回采参数,提出一种新型斜坡短臂采煤工艺,为该类复杂型煤层的开采提供借鉴。

长斜井衬砌智能化台车设计与应用研究

针对陡坡长、斜井多工作面同时开展衬砌的施工需求和现有台车的施工缺陷,文章以滇中引水香炉山隧洞2号施工支洞为研究对象,结合应用于公路、铁路等平洞的数字化、智能化整体液压钢模台车设计理念,应用智能化步履行走式整体液压台车,实现了斜井台车定位智能化和安全状态自动监测,大大提高了陡坡斜井衬砌效率和质量。

大坡段俯斜开采综放工作面运输机窜动及防倒架管理

为了研究运输机窜动控制及防倒架管理方法,分析、探讨控制运输机窜动的主要原因,结合综放工作面设备结构和采场条件,研究综放工作面运输机上窜下滑控制及架型调整的具体方法。结果表明,除了常用的“伪斜法”辅以“单向推溜法”控制运输机窜动以外,还要做好日常架型的管理,以及介绍架型管理及防倒架的具体方法,对综采工作面运输机上窜下滑、架型管理及防倒架管理具有借鉴意义。

Mechanical response of bridge piles in high-steep slopes and sensitivity study

The bridge piles located in high-steep slopes not only endure the loads from superstructure, but also the residual sliding force as well as the resistance from the slope. By introducing the Winkler foundation theory, the mechanical model of piles-soils-slopes system was established, and the equilibrium differential equations of pile were derived. Moreover, an analytic solution for identifying the model parameters was provided by means of power series method. A project with field measurement was compared with the proposed method. It is indicated that the lateral loads have great influences on the pile, the steep slope effect is indispensable, and reasonable diameter of the pile could enhance the bending ability. The internal force and displacements of pile are largely based upon the horizontal loads applied on pile, especially in upper part.

倾斜抗滑桩护坡承载特性试验研究

为充分探究倾斜抗滑桩护坡承载特性,弥补倾斜抗滑桩在相应试验研究方面的不足,采用模型试验方法,对倾斜与竖直抗滑桩支护结构的受力状态、坡顶沉降位移、桩身内力变化规律和桩后土压力进行测量对比分析。试验结果表明倾斜桩体桩后土压力随着桩体埋深的增加先增大后减小,其形态类似于抛物线型分布;桩体在同一位置不同加载荷载下,土压力值随着荷载的增大而增大,与竖直桩体相比其受力更加合理,更能充分发挥抗滑桩护坡作用。桩身弯矩形态近似呈“S”形分布,桩身弯矩随着桩体埋深的增加先增大,后出现弯矩重分布现象反向增大最后减小,在桩体埋深为35 cm处,弯矩值出现重分布现象;桩体在同一位置不同加载荷载下,弯矩值随着荷载的增大而增大且桩顶处弯矩值大于桩底弯矩。倾斜比竖直桩体在相同状况下所受弯矩值明显小很多,即能承受更大的土体作用而不发生破坏,从而使护坡效果明显增强,为在实际工程中采用与坡面大致垂直的抗滑桩比竖直抗滑桩能达到更好的护坡效果提供了理论指导。

顺倾软弱起伏基底内排土场边坡稳定性影响因素分析

为了更有效地指导内排土场边坡参数的动态优化设计,最大限度利用内排空间,结合霍林河南露天矿工程实际,应用刚体极限平衡法,分析了边坡形态、基底倾角、断层落差等因素对内排土场边坡稳定性的影响,获得了规律性认识;将得到的规律应用于霍林河南露天矿内排土场边坡参数设计,并应用数值模拟手段进行验证。研究结果表明:顺倾软弱起伏基底内排土场边坡稳定性与边坡高度、边坡角、基底倾角呈负相关,与断层落差呈先降低后升高、与断层相对坡脚距离L呈先升高后降低关系;随着内排土场推进距离的逐渐增加,边坡滑坡模式由上部边坡沿下盘基底切层–顺层滑动转变为从下部边坡沿上盘基底切层–顺层滑动;霍林河南露天矿内排土场边坡高度216 m、边坡角20°、基底倾角5°的工况下,断层落差为30 m时,其稳定性系数最小。