小间距隧道爆破动力特性试验研究   总被引：5，自引：2，他引：3  

张庆松  李利平  李术才  丁万涛  洪卫良 《岩土力学》2008,29(10):2655-2660

分岔隧道是一种新型隧道结构形式。以漆树槽分岔隧道为工程背景,进行了掘进爆破的围岩震动效应试验,通过不同掏槽结构下爆破震动作用隧道围岩衬砌质点振动速度的频谱分析与质点振动速度幅值的分布情况分析,对小间距公路隧道混凝土衬砌及其围岩在爆破地震波作用下的力学特征进行论述,重点研究了小间距隧道中隔墙及爆破掌子面的震动特性及变化规律。试验与分析结果表明,（1）中墙迎爆侧为振速峰值区,以水平径向振速最大,且沿着中墙走向呈现规律性变化;（2）掏槽孔爆破产生的地震效应最为强烈,其震动强度是扩槽眼和周边眼的2倍左右;（3）衬砌振速主振频率主要分布在低频段,以20～95 Hz为集中频段,高频地震波衰减极快;（4）同一测试断面中最大振速峰值出现在拱顶和边墙中部位置的概率最大,且大小比较接近,爆破掌子面附近的振速不适合萨道夫斯基预测公式,受爆破夹制及自由面的影响较大。  相似文献   

山岭隧道堵水限排围岩力学特性分析   总被引：10，自引：4，他引：6  

王秀英  谭忠盛  王梦恕  张弥 《岩土力学》2008,29(1):75-80

为了尽可能减少隧道长期大量排水带来的严重环境问题,高水位地区的深埋山岭隧道应采取“以堵为主,限量排放”即“堵水限排”的防排水设计准则。但在堵水限排情况下围岩的力学特性如何？是当前隧道衬砌结构设计急需解决的关键问题之一。首次建立了山岭隧道堵水限排情况下围岩力学特性分析的解析模型并进行了理论推导,分析了不同排水工况下围岩力学特性的变化并绘制了相应的围岩特征曲线,为堵水限排衬砌结构设计提供了理论依据。  相似文献   

Finite strain elastoplastic solutions for the undrained ground response curve in tunnelling          下载免费PDF全文

Apostolos Vrakas  Georgios Anagnostou 《国际地质力学数值与分析法杂志》2015,39(7):738-761

The instantaneous response of saturated low permeability grounds to tunnel excavation is important for deformations and stability close to the tunnel face. It is characterized by zero volume change in combination with the development of excess pore pressures. In tunnelling through poor quality ground under great depth of cover and high in situ pore pressure, heavily squeezing conditions (characterized by very large convergences) may occur soon after excavation. This paper presents exact finite strain analytical solutions for the undrained ground response around cylindrical and spherical openings that are unloaded from uniform and isotropic initial stress states, on the basis of the Modified Cam Clay (MCC) model and the Mohr–Coulomb (MC) model. The solution for a Drucker–Prager material is also given as it requires only a very small modification to the MC solution. The so‐called ground response curve, that is, the relationship between the support pressure and the cavity wall displacement, is derived in closed form for the MC model. The solution for the MCC problem is semi‐analytical in that it uses the trapezium rule for the computation of a definite integral. The influence of the significant parameters of the problem on the predicted deformation behaviour is shown by means of dimensionless charts. Finally, the practical usefulness of the solutions presented is illustrated by applying them to the breccia zones of the planned Gibraltar Strait tunnel – an extreme case of weak, low permeability ground under high pore pressure. The solutions can serve as a trustworthy benchmark for numerical procedures that incorporate material and geometric nonlinearities. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

浅谈城市过江隧道沉降监测实践中的体会     

孟庆来  李琦  刘振宇 《测绘与空间地理信息》2014,(10):226-229

城市构筑物沉降现象,在我国各大、中型城市中普遍存在。本文以上海市城市过江隧道沉降监测为例,论述了利用二等水准测量方法进行隧道沉降监测（城市沉降监测的一种）的实践过程,总结了城市隧道沉降监测工作中的一些具体做法和经验,对掌握沉降规律、预测沉降趋势具有积极的现实意义。  相似文献   

Experimental study on the hydrodynamic forces induced by a twin-propeller ferry during berthing     

Teresa Abramowicz-Gerigk   《Ocean Engineering》2008,35(3-4):323-332

The paper presents the experimental study on the influence of wall effect on the hydrodynamic forces induced by the propellers and thrusters of a ferry during the berthing. The program of the model tests was developed for the twin-propeller, twin-rudder, man-manned model of a car–passenger ferry in 1:16 scale, equipped with two bow thrusters. The different combinations of the operational settings of bow thrusters and propellers operating in the push–pull mode allowed to observe and quantify the variation of the hydrodynamic forces due to the changes of the water depth to draft ratios and distances to the quay. The results of model tests are introduced and discussed in the paper. The difference between the measured total hydrodynamic force and superposition of the component forces induced by the propellers and thrusters has been investigated. According to the structure of the generally accepted modular manoeuvring model, the proposition of the weight factors for the component forces comprising the interaction effects has been introduced and discussed.  相似文献   

2D and 3D upper bound solutions for tunnel excavation using ‘elastic’ flow fields     

Assaf Klar  Ashraf S. Osman  Malcolm Bolton 《国际地质力学数值与分析法杂志》2007,31(12):1367-1374

This paper presents 2D and 3D upper bound solutions for the problem of tunnel excavation in soft ground. The solution invokes the use of incompressible flow fields derived from the theory of elasticity and the concept of sinks and sources. Comparison is made with previously published results. For some geometries the current calculation results in lower (better) upper bound values; however, the results were generally close to previously published values. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

新型职业农民对城市郊区耕地利用“大棚化”转型的影响——以南京市为例     

闫梦露  王柏源  赵小风  钟太洋 《地理科学进展》2019,38(9):1294-1304

随着中国农业商品化转型的不断发展,传统露天种植模式逐渐被取代,城市郊区大棚面积迅速扩张,出现较为普遍的耕地利用“大棚化”转型。与此相随,耕作者也由传统“自给自足”型农民为主逐步转变为面向市场的“新型职业农民”。然而,到目前为止,少有研究分析新型职业农民在城市郊区耕地利用“大棚化”转型中扮演的角色。论文以南京市为例,基于2018年郊区291份农户问卷调查的一手数据,构建Logistic回归模型,研究微观尺度下新型职业农民对大棚化转型的影响。结果表明：① 新型职业农民是影响郊区耕地利用大棚化转型的根本因素,其中外来职业农民大棚化种植的可能性是其他类型农民的4.7倍左右;② 新型职业农民的务农年数和经营规模对大棚化转型具有显著的正向作用,其年龄对大棚化转型的作用方向相反;③ 对研究区所有农民而言,销售占比和单位面积耕地农业年度纯利润对大棚化转型具有显著正向作用。此外,相较于坡地和梯田,平地更加有利于农民大棚化种植。  相似文献   

An In-Situ Study on the Influence of Ascidian Suspension Feeding on the Subtidal Nepheloid Layer in the Northern Adriatic Sea     

Mark G. J. Hartl  & Jörg A. Ott 《Marine Ecology》1999,20(3-4):359-372

Abstract. In order to evaluate the effect of epibenthic suspension-feeding organisms on nepheloid-layer processes, a novel flow-through 'Benthic Ecosystem Tunnel' was used on sublittoral marine sediment substrate. Our test organism was the ascidian Microcosmus sulcatus . Particle and chlorophyll a reduction were recorded. The correlation of seasonal fluctuations of chlorophyll a concentrations with chlorophyll a reduction by M. sulcatus indicates the potential for Microcosmus to control local phytoplankton input to the subtidal nepheloid layer. However, the relatively low density of Microcosmus at the study site, the nature of the sediment surface and the susceptibility of ascidians to high turbidity ( i.e. , high sedimentation rates of total particular matter (TPM) causing frequent periods of siphon closure and inactivity) makes it unlikely that M. sulcatus is an important element controlling the composition of the nepheloid layer on a large scale.  相似文献   

小净距隧道中夹岩对拉锚杆控制机制与工程应用     

李然  王圣涛  张顶立  陈平  潘红桂  李奥 《岩土力学》2022,43(7):1865-1876

小净距隧道中夹岩受到两侧开挖的剧烈扰动,处于单向或双向受力的不利状态,严重影响施工安全,而预应力全长注浆对拉锚杆常用于中夹岩的主动支护。为阐明对拉锚杆的作用模式和控制机制,建立相应的力学模型和解析方法,开展实测验证,并进行参数分析和工程应用。研究表明：对拉锚杆为中夹岩提供强力水平约束,并提高岩体力学性能,发挥挤压加固作用;对拉锚杆利用剪切摩阻改善浅层围岩受力状态,同时锚固深部岩体,具有承载传力效果;对拉锚杆轴力和剪应力均由两侧向中间非线性衰减,作用范围局限于浅层中夹岩,实测结果验证了理论方法的合理性;进行了对拉锚杆的参数分析,提出了对拉锚杆临界长度、合理锚杆直径等工程建议;结合京张高铁长城站小净距隧道实践,主动增强对拉锚杆设计参数,变更后围岩压力、拱顶沉降和水平收敛的实测均值分别降低12.2%、14.1%和10.2%,保障了隧道开挖的安全。  相似文献   

狮子洋主航道水平勘察孔测井评价方法研究与应用          下载免费PDF全文

李军  李勇  谢小国  王军朝  李维  罗兵  莫家齐 《探矿工程》2022,49(6):21-29

为解决狮子洋主航道洋底深埋长隧洞精准勘探难题,在狮子洋主航道特大水垂比大位移科学钻孔（SZYSD-1S）中,采用存储式测井系统,通过获取自然伽马、电阻率、井深、井温、井斜等参数,利用测井数据交汇精准划分地层岩（土）性,结合垂直钻孔与本孔地质情况精准判识隐伏断层、划分围岩级别与风化程度、岩体渗透系数和渗透性,建立了一种用于深埋长隧道（洞）的小直径地球物理测井评价方法。SZYSD-1S孔测试结果表明,第四系与白垩系地层岩（土）性、断层破碎带的测井响应特征差异明显,岩体完整性系数为6%~82%,岩体质量为较完整-极破碎4个级别,风化程度为全风化-弱风化等4类,渗透系数为1.01×10^-7~1.18×10^-3 m/s,渗透性为弱透水-强透水,测井评价结果与实际试验结果基本一致。该方法是实现洋底深埋长隧洞精准勘察的一种必要手段,有效支撑服务粤港澳大湾区建设。  相似文献