Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an experimental investigation and stability analysis

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

Stability analysis for main roof of roadway driving along next goaf

Focusing on the stability of surrounding rock around the roadway driving along next goaf with a narrow coal pillar, a mechanics model of the triangle block structure of main roof above the roadway is established, and the sliding stability coefficient K 1 and the rotation stability coefficient K 2 are proposed to describe the stability of the triangle block structure quantitatively. The structure can keep a self stability before and after the roadway excavation, at the stage of mining induced effect, the stability of the structure is lowered, and the structure may become instability with decreasing the coal strength, increasing the mining height of working face and the mining depth.

Numerical analysis on stability of surrounding rock mass around deep roadway

Numerical simulations of the deep roadway were carried out through application of the strain-softening constitutive model. Differences between the deep and shallow roadway of the rock bearing structure were analyzed. Influences of the supporting resistance on the rock bearing structure at the deep roadway were discussed. The results show that there is alternation of strong and weak strength-softening region in the surrounding rock of deep roadway. However, the increase in the supporting resistance cuts down the size of strength-softening region of surrounding rock, decreases its strength-softening degree, and im- proves the stress distribution condition of the surrounding rock mass. It is concluded that the supporting resistance can raise the self-supporting ability of surrounding rock through controlling its strength-softening so as to make the rock bearing structure of deep roadway stable.

Stability analysis and control technology of gob‑side entry retaining with double roadways by flling with high‑water material in gently inclined coal seam

To ameliorate the defects of insufcient support resistance of traditional roadside flling bodies for gob-side entry retaining(GER),overcome the inability to adapt to the deformation of surrounding rock,and isolate the goaf efectively,a new type of high-water material as a roadside flling body for GER technology with double roadways was proposed.The instability analysis and control technology of GER with double roadways by flling high-water material into a gently inclined coal seam were studied.The basic mechanical properties of the new high-water material were investigated through laboratory experiments,and their main advantages were identifed.The reasonable width of the roadside flling wall of a high-water material was obtained by combining ground pressure observation and theoretical calculations.The distribution characteristics of the stress and plastic zone of surrounding rock of GER after being stabilized by the disturbance of the working face were studied using numerical simulations,and the failure range of GER by flling with high-water material was revealed.Based on this,a coupling control technology of anchor cables and bolts+single props+metal mesh+anchor bolts is proposed.Through the coupling methods of arranging borehole peeping and observing the convergences of surrounding rock,the results demonstrate that GER with double roadways by flling with a 1.8-m-wide high-water material has a good control efect.The above research will play an active role in promoting the application of high-water materials in GER roadside flling.

Primary Investigations on Yangtze River Bank Slope Stability in Wanzhou for the Three Gorges Reservoir Project

This paper investigates the main factors contributing to bank slope failures, such as the structure of rock and soil, water level change, bank slope gradient, vegetation, weathering and human activities. Based on these investigations, the bank slope failure models are analyzed. The stability of bank slopes in Wanzhou is investigated using geological surveying, 2D resistivity imaging surveying, excavated trenches and other methods. Finally, the disasters of bank slope failures in Wanzhou were investigated in detail. The results show that instability problems might occur in 60.38 km of bank slopes when the water level rises to 175 m. It is suggested that 37.8 km of unstable bank slopes should be stabilized, and 14.2 km of unstable banks should be moved or avoided after further geological surveying and reconnaissance. These results provide scientific basis and reliable data for the government to develop the third geodisaster prevention plan for the Three Gorges reservoir.

Quantitative analysis of parameters’influence on the stability of coal roadway clamped by upper and lower soft rock with extra thickness

In this paper,a physical model of coal roadway which is clamped by upper and lower softrock with extra thickness was built according to the characteristics of soft rock strata in china's western mining area.Then,a series of orthogonal numerical experiments were carried out by selecting the strength and stiffness parameters of soft rock and coal seam as well as the in situ stress of soft rock strata as experimental factors and roadway displacements(convergence displacements of sides,displacement of roof to floor)as experimental indexes.By constructing the F statistics with different inspection levels,evaluation method for influence of the experimental factors on stability indexes were defined.Thus,influence degrees of specified parameters on the stability of roadway were divided into five classes as follows:highly significant influence,significant influence,relatively significant influence,little significant influence,and no influence respectively which realize the quantitative analysis of the influence degrees of experimental factors.The finite element calculation results showed that main failure mode of coal roadway that usually showed as tension failure of coal seam in roof and deformation factors of coal seam had the most remarkable effect on roadway displacements.The conclusions provide theoretical basis for further analysis of the mechanism of"roof burst"in roadway maintenance.

潞安煤矿2605工作面巷道支护方案优化设计与研究

现场调研、数值模拟、理论分析相结合的方法,结合现场工程实践,对潞安漳村2605工作面巷道稳定性进行研究。选取2605工作面运巷、中风巷和进风巷为研究对象,根据相关地质资料,设计支护方案;对区域巷道变形破坏进行数值模拟分析,包括顶板下沉量、巷道两帮收敛及锚杆锚索工作载荷等。得到各支护方案的巷道变形破坏结果,并结合数值模拟结果确定2605工作面巷道的合理支护方案。

基于关键块体的井巷围岩稳定性分析及支护研究

为了进一步研究关键块体对巷道围岩稳定性的影响及通过关键块体分析进行支护措施的设计。以蒙库铁矿地下开采某一巷道为研究对象,通过工程地质调查与现场测试工作,对围岩节理裂隙统计与分段,并进行岩块强度试验和岩体的波速测试,获得了岩体完整性参数,依据此进行了详细的岩体工程分级,给出不同岩体的分级力学参数,再通过Unwedge进行关键块体分析,对不稳定岩块进行划定,确定了锚喷支护的参数及重点支护位置,然后采用有限元软件模拟开挖过程并分析了开挖过程中围岩及支护的应力应变变化情况,最后进行现场采动应力的监测与分析。研究结果表明:经过关键块体分析,更准确地辨别出可能导致巷道失稳的不稳定岩块,针对关键块体分析结果提出稳定性支护措施,并应用于现场,进行采动应力监测与分析,取得了良好的效果。研究结果在一定程度上为围岩稳定性分析及支护设计提供了可靠依据。

原位剪切试验在工程滑坡勘察中的应用

岩土体的抗剪强度指标,尤其是作为薄弱层的岩体结构面的抗剪强度,在滑坡稳定分析中起着至关重要的作用。现场原位剪切试验,试样受扰动小,试验状态与岩土体所处真实状态较为吻合,得到的参数也更加真实,是滑坡勘察原位测试的重要手段之一。适用于测定边坡的岩土结构面、岩土接触面、滑动面以及含碎石黏土的混合土层和其他粗颗粒土层的抗剪强度。重庆华宇·观澜华府项目工程滑坡勘察,在现场做原位剪切试验的同时,采集原状样品进行室内直剪试验,获取2种不同试验下的抗剪强度参数,分别取用2种参数对不同工况下的滑坡体进行稳定性分析计算,并与滑坡体的实际变形特征进行比较,从而验证了原位剪切试验确定岩土体抗剪强度参数的合理性,可为类似工程提供参考和借鉴。

基于FLAC3D的开采扰动下巷道稳定性研究

近矿体巷道围岩稳定性与开采扰动密切相关,本文以大柴旦矿业有限公司青龙沟北矿段深部西矿体及3280北风井回风巷道为主要研究对象,基于现场地质调查和室内岩石力学试验,对岩体质量进行分级和岩体力学参数进行估算;依据矿山生产计划,建立数值计算模型,分析位移规律及采动应力演化过程。结果表明:随着深部西矿体开采工作的进行,巷道变形整体较小,并向采场方向倾斜移动;随着开采深度增加巷道右帮、拱肩应力集中区域与顶板应力较低区域呈顺时针转动,在开采完5个中段后后续矿体的开采对巷道周围应力分布影响较小;3280北风井回风巷道及左侧斜坡道、二者间联络道出现了应力集中现象,针对千枚岩岩体质量较差应在全面了解该区域岩体质量后进行支护优化设计。

线性水利工程社会稳定风险调查工作要点

风险调查是社会稳定风险分析的基础性工作,是识别项目风险因素、制订风险防范化解措施、判断风险等级的重要依据。本文结合线性水利工程的突出特点,从风险调查的内容和重点、调查方法的选择、调查的准备工作、调查组织实施要点等方面,对线性水利工程社会稳定风险调查工作的要点进行了探讨。

降雨作用下三维矿山边坡的力学状态响应

矿山边坡稳定性是影响矿山开采的重大安全生产难题,安全的环境是进行矿山开采的重要前提,因此,开展矿山边坡稳定性分析,对矿山的安全生产具有重要的指导意义。以重庆皇华石灰岩矿山边坡为例进行数值建模分析,首先利用无人机倾斜摄影得到矿山边坡几何形状并识别出岩体结构面,基于摄影识别结果建立三维地质模型,然后采用有限元强度折减法对边坡进行数值计算,对比分析天然工况及暴雨工况下矿山边坡稳定性,揭示降雨作用对于边坡稳定性的影响规律。结果表明,暴雨工况下边坡变形和应变比天然工况下的更大,安全系数更小;暴雨工况下的变形和应变分别比天然工况高30%、40%~60%,安全系数减小了5%~7%,数值模拟结果基本合理;该矿山边坡稳定性较高,整体滑移破坏的可能性较低,但需防范局部块体掉落的风险,还需要进一步研究是否需要进行局部边坡加固。研究结果验证了现场调查、室内试验、三维模型判定、二维剖面重点分析的综合研究方法对岩质边坡稳定性进行评价的适用性与可靠性。

掘进扰动下巷道冒落特征研究

针对某矿山因掘进扰动冒落问题,采用FLAC和PFC3D耦合程序,计算了联络巷道在掘进过程中的冒落特征和冒落区范围,得出:掘进过程中自5#斜井开始,冒落会持续发生,初始冒落范围为5#斜井与联络道交岔点的位置;联络道为冒落的高发区域,主要表现为顶板冒落,自联络巷道掘进开始至6#斜井掘进完成,冒落会持续产生,不易控制,冒落区较大,为相同条件地下矿山开采提供一定参考。

浅埋纵向交叉巷道潜在失稳模式分析

针对某矿山运输巷道持续大面积冒落问题,通过数值分析的方法,利用FLAC和PFC3D耦合程序,计算了巷道不同暴露时间下与充填后冒落分布情况,表明冒落会持续发生,随着暴露时间的增加,联络道及5#巷道中的冒落持续发展,其中以第一个月的冒落最为严重,冒落集中区以联络道及其交岔点的部位居多,为相同条件地下矿山开采提供一定参考。

高边坡勘察新技术在水利工程中的应用现状、挑战与展望

随着大批超高边坡工程的兴建,高边坡失稳灾害风险日益凸显,传统勘察技术难以满足精细化、定量化分析需求,亟须发展新理论和新技术。系统综述了近年来高边坡勘察领域的关键技术进展。在遥感技术方面,无人机倾斜摄影测量、热红外成像等提供了精细刻画边坡地质结构的新途径;在钻探技术方面,定向钻探、绳索取芯、CT扫描等实现了钻芯的定向获取与精细结构表征;物探方面,多种方法的联合反演、多源数据的协同反演是研究热点;原位测试、CT扫描等新型岩土试验技术不断涌现。同时,考虑结构面影响的有限元法、非连续变形分析法、基于动力学的离散元法、多场耦合分析法等为边坡稳定性评价提供了更加精细和量化的工具。未来,随着大数据、人工智能、物联网、5G等现代信息技术与传统勘察技术的深度融合,智能化、体系化将成为重要发展方向。建议加强跨学科交叉研究,发展多尺度、全过程、定量化的高边坡勘察理论与方法,为水利工程高边坡灾害防治提供关键技术支撑。

地下水封洞库施工巷道支护结构稳定性分析

以“湛江国家石油储备地下水封洞库工程”为依托,对施工巷道局部支护方案进行分析并通过有限元数值模拟计算的手段对该处支护方案进行校核得出锚杆、喷层、钢拱架与围岩共同承担开挖荷载。边墙腰部位置的锚杆应力较大,最大数值为288.705 MPa;喷层则主要承受压应力,在喷层拱座位置压应力最大,数值为–7.638 MPa,为局部的应力集中区域,其余位置的喷层压应力约为–2.546~–0.850 MPa,计算结果均在材料的设计强度范围内。洞内开挖过程中由于洞内施工致使地下水位下降,出现地表土体开裂,在表面进行固表灌浆效果较好,现场施工中针对局部变形较大情况加强拱脚支撑,增加锁拱锚杆,或加水平横撑等措施均能达到控制变形的目标。

基于PLAXIS的高陡边坡勘察及稳定性分析研究

高陡边坡的稳定性是岩土工程中的关键问题,直接影响到工程的安全和可靠性。本研究采用PLAXIS有限元分析软件进行高陡边坡的稳定性分析。首先建立了详细的地质模型,并模拟了实际边界条件和岩土参数,以评估边坡的稳定性。通过对比分析不同条件下的模拟结果,识别影响高陡边坡稳定性的关键因素,并提出了有效的评价方法。研究结果表明,边坡的物理和力学参数是决定其稳定性的主要因素。最后,基于分析结果,本文提出了针对性的工程建议和后续研究方向,旨在提高边坡工程的设计和施工质量。

市政道路土岩组合边坡勘察要点解析及边坡稳定性分析

对市政道路土岩组合边坡勘察要点进行了深入细致的解析,对工程地质测绘和调查的方法及内容进行了分析,对土岩组合边坡勘探线、点进行了科学合理的布置,对主要岩土层及岩体结构面均提供了满足工程需要的边坡力学参数,对土岩组合边坡稳定性进行了全方位评价,对边坡可能存在的各种破坏模式进行了系统深入的计算分析,解决了工程实践中如何进行土岩组合边坡勘察及边坡稳定性分析的问题,其可为类似土岩组合边坡勘察及边坡稳定性分析提供借鉴和参考。

三山岛高应力腐蚀环境裂隙围岩支护技术与控制研究

针对三山岛金矿深部开采面临的高应力腐蚀环境下围岩稳定性问题,分析了当前支护下管缝式锚杆锚固力腐蚀退化过程,提出了深部高应力腐蚀环境围岩控制的树脂锚杆支护方案,综合采用工程类比、经验公式和理论计算3种方法确定了树脂锚杆支护参数。同时,采用FLAC^(3D)数值模拟方法,分析了管缝式锚杆支护、树脂锚杆支护和锚网穿带(树脂锚杆+锚网+穿带)支护3种形式下的围岩应力与变形特征。结果表明:锚网穿带支护下的围岩变形控制效果最优,树脂锚杆支护次之,管缝式锚杆最差。此外,在深部-1005 m水平腐蚀环境下采用锚网穿带进行支护试验,并对围岩应力、变形、支护状况进行监测,监测点1~3在监测周期内巷道最终水平收敛平均值为23 mm左右,巷道顶板平均下移量为25 mm。通过监测结果可知,该支护方案对巷道围岩的稳定性起到了预期的岩层控制效果。

国际水电工程地质勘察实践探讨

作为国际水电工程勘测设计的主要基础性资料,地质勘察成果的国际工程咨询审批进度往往对工程进度甚至成本有较大影响。在总结对标研究工作成果、中国水电技术标准“走出去”之工程测量与地质勘察篇研究成果的基础上,结合国际水电工程地质勘察实践,对地震参数确定、坝基岩体力学参数确定、边坡稳定分析、洞室围岩分类及支护建议等关键技术问题进行了初步分析,总结了中外技术标准的主要差异,初步提出了探讨性的对策及建议,可供业内人士参考。