高能级强夯室内模型试验研究

基于相似理论,自行设计了室内模型试验装置,利用该装置对3000kN.m8、000kN.m和10000kN.m能级强夯开展了室内模型试验研究。研究结果表明：强夯的动应力在锤底有变化,夯锤两侧的动应力几乎为零。随着夯击次数的增加,在锤底浅层土体形成应力集中层,在该集中层上,动应力的增幅较为明显;动应力随着深度的增加而衰减,...     

武广高铁某涵路过渡段动力特征分析

以武广高铁密集涵洞过渡段为例,建立了列车-轨道耦合的三维动力学分析模型,分析了350km/h高速行车条件下过渡段路基的动力响应特性。分析表明:①过渡段路基基床表层、底层的竖向振动的位移、速度、加速度均在涵洞顶最小,在涵洞侧面出现较快速增长;动应力的变化趋势则与之相反,在涵洞顶最大,涵洞两侧逐渐降低。②动响应沿路基深度呈指数函数形式衰减,基床表层至基床底层衰减较快,路基面下1m左右动响应幅值衰减渐趋于平缓,路基面下3m动响应衰减基本趋于稳定。其中振动加速度衰减最为明显,动位移、振动速度、动应力衰减则相对较缓。现场实车试验测试值与仿真计算值较为接近,表明采用的仿真分析方法较为可靠。     

刚性路面结构动力反应的试验研究

叙述在美国明尼苏达州Mn/ROAD研究设施进行的刚性路面动力反应试验研究工作。试验中选择了三个刚性路面研究断面,通过采集两种重量的卡车以不同速度通过时,刚性路面板不同位置和不同深度部位处动应变计、缩缝传力杆钢筋应变计的应变时域变化曲线和路基顶面动土压力计的土压力时域变化曲线,获得了刚性路面板顶面和底面的纵向和横向动应变特征、缩缝传力杆动应变特征和路基顶面动土压力特征以及影响刚性路面板动应变特征的参数等的测试数据,为进行理论分析提供了重要基础。     

受力模式对沥青混合料动态模量的影响

采用不同受力模式对3种沥青混合料进行动态模量试验,分析了受力模式、围压、应变水平等因素对沥青混合料动态模量主曲线的影响,通过Fillers-Moonan-Tschoegl模型和改进Sigmoidal模型建立了沥青混合料移位因子-围压和动态模量围压之间的函数关系式.结果表明:二次拟合可以消除沥青混合料动态模量主曲线上动态模量极值对移位因子计算模式的依赖;在相同换算频率时,沥青混合料单轴压缩、间接拉伸和四点弯曲动态模量有差别,在低温高频段更明显,但三者之间存在较好的线性关系;在高温低频段,围压对沥青混合料三轴压缩动态模量的影响较显著;沥青混合料四点弯曲动态模量对应变水平变化较为敏感.     

Numerical simulation on rockburst of underground opening triggered by dynamic disturbance

The dynamic disturbance, which is termed as the time-dependent loading such as explosion, vibration, stress impact from neighboring rockbursts, earthquakes, may trigger the rockbursts around the underground opening at depth. A numerical model capable of studying the dynamic failure process of rock under coupled static geo-stress and dynamic disturbance is proposed, and it is implemented into the Rock Failure Process Analysis (RFPA), a general finite element package to analyze the damage and failure process of engineering materials such as rock and concrete. Based on the consideration of the static geo-stress, the RFPA-Dynamics is used to simulate the rockburst that is deemed to be triggered by dynamic disturbance around the deep underground opening. The effect of lateral pressure coefficient and dynamic disturbance waveform on the development of failure zone around the underground opening is numerically simulated. The numerical results indicate that the dynamic disturbance is one of the most important mechanisms that trigger the rockbursts around underground opening. Therefore, it is of theoretical and practical significance to investigate the effect of dynamic disturbance on the rockbursts of underground opening, especially for the underground excavation at depth where the surrounding rockmass is highly stressed. The numerical results also reveal that the contribution of the dynamic disturbances is closely pertinent to both the static geo-stress condition and the waveforms of the dynamic disturbance. In general, dynamic disturbance brings about the greater influences on the stability of underground opening with its increasing magnitude and prolonged duration. However, with regard to the specific static geo-stress condition and characteristics of dynamic disturbance, the contribution of dynamic disturbance to trigger the rockbursts must be examined based on numerical analysis according to the specific geo-stress conditions and characteristics of the dynamic disturbance.     

强夯法施工工艺发展综述及对各种吹填土的适用性

本文首先简要介绍了强夯法的原理,然后以此为主线,分别介绍了强夯置换、低能级强夯、高能级强夯、动力排水固结法及动力主动排水固结法(预排水动力固结法)五种工法的原理、应用情况及适用条件,并分析它们相互之间的关系及对各种吹填土的适用性。从强夯法的演变发展历程中可以看出,一种工法伴随着工程的需要它应运而生,但它同时也必须不断地改进以适应新情况。     

基于温度变化的路基盐渍土动强度参数试验研究

基于英国GDS动三轴试验系统,对青海西部地区的路基盐渍土进行动三轴试验,在温度变化条件下探讨其破坏动应力、动黏聚力及动内摩擦角等相关参数随围压、频率的变化规律,建立了不同动载频率下破坏动应力-围压-温度关系曲面,得到了与温度相关的曲面拟合方程。试验结果表明：土-冰-盐的胶结作用对温度变化极其敏感,随着温度降低,盐渍土的破坏动应力明显增大;动黏聚力和动内摩擦角随温度的降低而增大。     

滨海含软土夹层粉细砂地基高能级强夯加固试验研究

滨海粉细砂场地地基常分布有软土夹层或淤泥包且地下水位较高,地基处理难度大。目前采用高能级强夯加固滨海粉细砂场地的工程案例较少。结合具体工程研究了某地下水位较高且含软土夹层的滨海粉细砂场地上开展的5、8、12、15MN·m能级强夯加固试验。除5MN·m能级强夯试验区外,其余试验区均先采取高能级点夯加固深层土体,然后采用中等能级点夯加固夯点间土,最后利用低能级满夯加固地基浅层。对比分析了夯沉量和强夯前后的旁压、静力触探测试数据,发现夯击7~8击后夯沉量变化明显减小,每遍的单点夯击击数宜控制在8~9;在有效加固深度范围内,土体的旁压模量和静力触探锥尖阻力均明显提升,高能级强夯能有效消除滨海粉细砂的液化势。试验场地内上述各个能级的有效加固深度分别为7.5、9、10.5、10m,在有效加固深度范围内,表征土体相对加固程度的提升系数沿深度大致呈直线下降。现场试验数据还表明,将地下水位降低到距地表以下2.5m有助于提高加固效果;软土夹层的存在会明显影响加固效果及限制有效加固深度的发展,因受软土夹层的影响,场地15MN·m能级强夯的有效加固深度明显偏小。建议在级配不良的滨海粉细砂场地上按照规范JGJ 79—2012中细颗粒土的标准来确定高能级强夯的有效加固深度。     

客运专线路基填筑质量Evd检测试验方法的探讨

介绍了国内外对动态变形模量Evd的研究概况,阐述了动态变形模量Evd的计算式、工作原理和操作步骤,分析了动态变形模量Evd的优点及其在国内的应用,可为动态变形模量Evd的推广应用提供一定的依据.     

强夯法加固煤矸石地基动应力模型试验研究

通过强夯法加固煤矸石地基物理模型试验,用 DH5939 动态应变仪完整地记录了强夯每一击作用下煤矸石地基中的 动应力 ,系统地研究了不同夯击能和夯击次数作用下不同深度煤矸石地基动应力的分布特征及其衰减规律。结果表明,在强夯冲击荷载作用下,动应力为单一的波峰,沿夯锤不同深度的动应力达到峰值具有明显的时滞性。强夯动应力在水平方向的衰减速度比竖直方向快,竖直方向的影响范围比平方向大。在相同的夯击能作用下,动应力峰值随深度衰减很快,近似呈负幂指数规律衰减。另外,对不同的测点,在夯击能一定的条件下,随着夯击次数的增加,有效加固范围内的动应力增加明显,但在 3 ～ 6 击后基本稳定。研究为精确模拟分析强夯加固机理提供了有效途径。     

Fatigue properties of intact sandstone samples subjected to dynamic uniaxial cyclical loading

In this paper, the fatigue behaviour of intact sandstone samples obtained from a rockburst prone coal mine and studied under dynamic uniaxial cyclic loading in the laboratory is presented. Tests were conducted on dry and saturated samples with loading frequencies ranging from 0.1, 1 and 10 Hz and amplitudes of 0.05, 0.1 and 0.15 mm. From the laboratory investigations, it was found that the loading frequency, as well as the amplitude, was of great significance and influenced the rock behaviour in dynamic cyclic loading conditions. The dynamic fatigue strength and the dynamic axial stiffness of the rock reduced with loading frequencies and amplitude. The dynamic modulus was found to increase with the loading frequency but decrease with the amplitude. In the case of the saturated samples, it was found that the dynamic fatigue strength reduced by approximately 30 per cent, while the dynamic Young's modulus reduced by about 20 per cent. From the presented study, the dynamic energy was found to be independent of the testing conditions while other rock properties were found to be dependent on these. Finally, it was concluded that rock would more readily succumb at low frequencies and amplitude than at high frequencies and amplitude for a given energy availability.     

Estimation of dynamic tensile strength of sandstone

A series of dynamic tests on Kimachi sandstone for measuring dynamic tensile strength are carried out using underwater shock waves. An emulsion explosive is used as the source of dynamic loading, and a pipe filled with water was arranged between the explosive and a cylindrical specimen. The length of the pipe is varied to produce different strengths of the incidence shock wave into the specimen. The velocity at the free end of the specimen and the position of a crack are observed using a laser vibration meter and a high-speed camera, respectively. A simple method of estimating dynamic tensile strength is proposed based on experimental results. The complete velocity profile at the free end without fracture information is completely constructed under a simple assumption. The point at which the crack may be markedly activated has been defined by the velocity profile at the free end as “the averaged fracture point”. Instead of the distance from the free end to the fracture position, the distance from the free end to the averaged fracture point is employed in estimating dynamic tensile strength. The dynamic tensile strength of Kimachi sandstone was obtained by an improved method within strain rates of 10–40 s⁻¹. This study has indicated that the dynamic tensile strength varies with strain rate to the 1/3 power.     

高速铁路路桥过渡段振动特性试验研究

通过某高速铁路试验段现场动载试验,测试过渡段不同断面、不同深度处路基的动应力、弹塑性变形和路基综合动刚度,分析在模拟列车动荷载作用下的动态反应和工程特性。测试结果表明:①级配碎石基床表层对过渡段路基动应力的衰减效果明显,基床表层动应力衰减系数沿纵向逐渐减小,基床底层则逐渐增大;②各断面弹塑性变形主要集中在基床表层,沿纵向呈增大趋势,沿深度逐渐减小;③路基综合动刚度与基床表层、底层、路堤本体的刚度有关。过渡段路基从动应力传递规律、弹塑性变形、路基综合动刚度等方面起到了过渡作用。     

偏压隧道洞口边坡地震动力反应及稳定性分析

用动力有限元法研究了偏压隧道洞口横向边坡在水平地震、垂直地震以及水平和垂直地震同时作用下的全时程动力反应规律。在动应力计算结果的基础上,叠加静应力场,分析三种工况下最危险滑动面的动力安全系数时程,并采用平均动力安全系数法和地震永久性变形评价洞口横向边坡的地震动力稳定性,最终建立了偏压隧道洞口横向边坡的地震动力响应分析及稳定性评价模型。     

深部高应力动压巷道支护方法研究

深部高应力巷道的支护方法是目前的工程难点问题。中平能化集团十二矿31010己15煤层皮带巷和回风巷埋深超过1 000m,同时将承受上部保护层开采的动压作用,巷道稳定性不易控制。首先通过地应力测试和围岩松动圈测试,得知巷道为高地应力环境下大松动圈巷道;之后通过三维数值计算分析,获得了上部保护层开采过程中下部巷道的矿压显现规律,得知巷道将受到高应力动压作用。针对此巷道高应力动压特点采用卸压让压以及高强锚索的联合支护方法,即在围岩卸压让压的基础上采用高强锚索进行加强支护,同时采用单体柱进行局部临时加强支护。现场工业试验结果说明卸压让压以及高强锚索组成的联合支护系统可用于深部高应力动压巷道的稳定性控制。     

输水管道水锤效应作用下斜拉桥结构动力响应研究

为研究斜拉桥上铺设的大型输水管道发生水锤效应时桥梁结构的动力响应,以某独塔斜拉桥为工程背景,根据水锤效应的基本理论和作用方式,将管道对桥梁的动力效应简化为一随时间变化的动力荷载。通过分别建立管道水锤计算模型和桥梁动力计算模型,得到水锤效应发生时阀门位置顺桥向冲击力随时间的变化情况,再将此冲击力作为动力荷载施加到桥梁模型上。计算结果表明：水锤冲击力随时间呈周期性变化,阀门短时间关闭时将产生较大的冲击荷载;漂浮体系独塔斜拉桥各构件在水锤冲击作用下的动力响应以顺桥向方向为主,同时伴随有竖向的位移与应力。主梁上的应力变化可忽略不计,桥塔及斜拉索中应力变化分别可达0.7MPa和1.5MPa左右。单侧布置的管道还会产生偏心作用,使结构的动力响应呈现非对称性。     

浅析湿陷性黄土地基的处理方法

阐述了湿陷性黄土的性质,介绍了几种湿陷性黄土地基的处理方法,包括垫层法、强夯法、灰土桩挤密法、化学加固法、预浸水法等,以提高人们对湿陷性黄土地基处理方法的认识。     

软土地层地铁及地下构筑物抗震动力分析研究现状

从软土的动力特性、土 结构动力相互作用、软土地基的动力反应分析和地下结构动力可靠度计算等方面 ,介绍了国内外软土地层中地下构筑物的抗震动力分析研究情况。并介绍了笔者在这方面的一些研究成果     

Dynamic rock tensile strengths of Laurentian granite: Experimental observation and micromechanical model

Tensile strength is an important material property for rocks. In applications where rocks are subjected to dynamic loads, the dynamic tensile strength is the controlling parameter. Similar to the study of static tensile strength, there are various methods proposed to measure the dynamic tensile strength of rocks. Here we examine dynamic tensile strength values of Laurentian granite (LG) measured from three methods: dynamic direct tension, dynamic Brazilian disc (BD) test, and dynamic semi-circular bending (SCB). We found that the dynamic tensile strength from direct tension has the lowest value, and the dynamic SCB gives the highest strength at a given loading rate. Because the dynamic direct tension measures the intrinsic rock tensile strength, it is thus necessary to reconcile the differences in strength values between the direct tension and the other two methods. We attribute the difference between the dynamic BD results and the direct tension results to the overload and internal friction in BD tests. The difference between the dynamic SCB results and the direct tension results can be understood by invoking the non-local failure theory. It is shown that, after appropriate corrections, the dynamic tensile strengths from the two other tests can be reduced to those from direct tension.     

输电塔在断线荷载作用下的动力响应

目前,许多有关输电塔在断线荷载作用下的响应分析,都假定多根导线同时断裂,然而大多数情况下多根导线并不是同时断裂的。针对这个问题,本文采用有限元分析方法,对导线同时断裂和不同时断裂所引起的动力响应进行了分析计算,得到了不同情况下输电塔的动力响应规律。结果表明,导线断裂存在时间差时所引起的动力响应,比导线同时断裂引起的动力响应更加剧烈。然而,目前施行的杆塔设计规范,将断线荷载视为静力荷载,并未考虑断线荷载引起的动力效应,望本文内容可以为现行规范提供参考。