共查询到20条相似文献，搜索用时 140 毫秒
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目前实施的《公路隧道设计规范》（JTG D70－2004）对土质围岩分级、围岩亚级分级方法都没有进行研究,因此,不能满足隧道设计和施工的要求。通过对岩质围岩和土质围岩自稳性的大量室内试验、数值计算和理论分析,建立了公路隧道岩质围岩和土质围岩统一的亚级分级标准。研究结果显示：围岩自稳跨度是围岩自稳性的综合反映,围岩自稳跨度可分为长期稳定跨度、基本稳定跨度、暂时稳定跨度和不稳定跨度。研究表明,规范中岩质围岩的Ⅲ级、Ⅳ级和Ⅴ级分别依据自稳跨度可分为2个、3个和2个亚级;土质围岩尽管分为黏质土围岩、砂质土围岩及碎石土围岩,但按照各自的自稳跨度可以分别进行亚级划分。可见,以自稳跨度可以建立岩质围岩和土质围岩统一的亚级分级标准。 相似文献
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针对残破积碎石土斜坡浅层碎石的级配、粒径及其持水性等特征因素在降雨诱发滑坡中表现敏感,以湖南省湘潭市昭山区坡表碎石土中碎石为研究对象,应用图像处理分析了碎石颗粒的空间分布变异特征、粒度特征与复杂度,并结合强降雨模拟实验研究了堆积碎石(母岩为粉质砂岩)的持水特性。研究发现:坡表含石量在49.75%~77.63%之间,沿坡面向下降低;颗粒级配组成沿斜坡分布均良好,且坡脚的不均匀系数比坡顶大,不利于雨水入渗;圆度主要分布在0.6~0.9区间内,其累计平均值为93.4%,且圆度在0.8~1.0区间内沿坡面向下呈增加趋势,在0.5~0.8区间内则相反;块体长短轴比的平均值位于1.4~1.497之间,且沿坡面向下有变小趋势;碎石复杂度沿坡面向下有增加趋势。碎石的饱和吸水率均小于5%,且饱和吸水过程与降雨历时存在指数关系,碎石的饱和吸水率及饱和堆积碎石的滞留水量随着平均等效粒径的增加而减小。 相似文献
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本文对STW型高分子土壤稳定剂改良粘性土团聚体的水稳性进行了试验研究。结果表明,STW型稳定剂在低浓度(3%~9%)就可以大幅度提高粘性土团聚体的水稳性;在相同粒径条件下,团聚体水稳性指数K随着稳定剂浓度的增大而增大;在同一种稳定剂浓度作用下,团聚体水稳性K随着粒径的增大而减小。根据改良前后团聚体的崩解特点,提出了渐进式和炸裂式两种团聚体崩解模式,并对STW型高分子土壤稳定剂改良粘性土团聚体的机理进行了分析。 相似文献
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为研究基于当地历史降雨数据在不同降雨强度下的碎石土高路堤边坡的稳定性,分析了边坡降雨入渗的方法及模型,讨论了碎石土高路堤边坡的稳定性计算方法,以甘肃陇南地区为研究对象,基于Geostudio对不同计算方案下的碎石土高边坡进行降雨入渗及稳定性分析,得到了不同降雨强度下的碎石土高路堤边坡的稳定性.研究结果表明,基于研究区降... 相似文献
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采用一维积水垂直入渗法测定含碎石土壤的入渗过程,分析碎石含量和碎石组成对土壤水分运动影响。对试验数据采用Kostiakov入渗公式拟合,得出反映入渗速率的拟合参数比值与土石比成幂函数关系;采用简略的Philip垂直入渗方程幂级数解拟合湿润峰随时间的变化,拟合精度高,并发现拟合参数与土石比仍成幂函数关系。采用简单相关分析碎石粒径对入渗过程影响,得出粒径2~3 mm碎石与入渗过程成显著的负相关关系,而>25 mm碎石有利于入渗。研究结果可为含碎石土壤的水循环提供重要的基础。 相似文献
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含碎石紫色土坡面降雨入渗和产流产沙过程 总被引：7，自引：0，他引：7
在室内土槽模拟降雨试验基础上,观测了具有不同碎石体积含量紫色土的降雨入渗地表产流产沙量以及细沟间径流和细沟径流的流速,以期建立碎石含量与土壤流失的定量关系。研究结果表明:土壤中碎石混合对降雨入渗有正负两方面的影响,当碎石含量为20%~30%时,碎石的存在增强土壤入渗能力,当碎石含量提高到30%时,土壤的入渗能力被削弱。土壤中碎石混合通过不同的作用机制对坡面细沟间径流流速和细沟径流流速产生不同的影响,随着碎石含量的增加,细沟间径流平均流速逐渐增加,细沟径流的平均流速逐渐降低。土壤中碎石混合通过改变土壤的物质组成和结构,增强土壤的抗蚀性和抗冲性,随着碎石含量的增加,径流含沙率和土壤流失量显著降低,土壤流失比与碎石含量呈极显著指数负相关关系。 相似文献
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在室内土槽模拟降雨试验基础上,观测了具有不同碎石体积含量紫色土的降雨入渗地表产流产沙量以及细沟间径流和细沟径流的流速,以期建立碎石含量与土壤流失的定量关系。研究结果表明:土壤中碎石混合对降雨入渗有正负两方面的影响,当碎石含量为20%~30%时,碎石的存在增强土壤入渗能力,当碎石含量提高到30%时,土壤的入渗能力被削弱。土壤中碎石混合通过不同的作用机制对坡面细沟间径流流速和细沟径流流速产生不同的影响,随着碎石含量的增加,细沟间径流平均流速逐渐增加,细沟径流的平均流速逐渐降低。土壤中碎石混合通过改变土壤的物质组成和结构,增强土壤的抗蚀性和抗冲性,随着碎石含量的增加,径流含沙率和土壤流失量显著降低,土壤流失比与碎石含量呈极显著指数负相关关系。 相似文献
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Twin tunnels are frequently used to address the increasing transportation demands in large cities. To ensure the safety of twin tunnels in close proximity, it is often necessary to take protective measures that have not been well studied. Field monitoring was conducted for a project of twin earth pressure balance shield (EPBS) tunnels in typical soft ground. The preceding tunnel was reinforced by various measures, including trailer bracing, compensation grouting, artificial freezing and scaffold bracing. The entire deformation of the reinforced tunnel was recorded during the succeeding tunnelling process. A three dimensional finite-element method (FEM) model was established to simulate the entire process of twin EPBS tunnelling, particularly the reinforcement measures. The computed deformations of the reinforced tunnel were consistent with the measured data. Furthermore, the stress history and pore pressure of the surrounding soil were analysed to investigate the deformation mechanism of the tunnel. Both the measured and computed results indicate that although the face pressure of the succeeding tunnel was smaller than the earth pressure at rest, the preceding tunnel could still experience an inward horizontal convergence and a deflection away from the succeeding tunnel. These distortion modes were caused by the squeezing effect of the horizontal soil arch in front of the succeeding tunnel face. Finally, convergence and deflection indices were proposed to quantify and assess the effectiveness of the reinforcement measures. The trailer bracing, as an “in-tunnel” reinforcement technique, was found to be the most effective method for controlling tunnel convergence. However, artificial freezing as an “out-tunnel” reinforcement technique led to the largest reductions in tunnel deflection. A combination of both “in-tunnel” and “out-tunnel” reinforcements was recommended. 相似文献
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The roadway tunnel is considered a good solution for the success of modern roadway networks. It can help to overcome possible traffic congestion and considerably reduce journey time. The continuous growth of traffic volumes leads to increase congestion and decrease safety. This leads to the need for extra tunnel space. The extra tunnel space can be achieved either by the widening of the existing tunnel or by adding a new one. The choice of the suitable method is dependent on many factors like tunnels alignment, site conditions, construction method, tunnel operation, risk assessment…etc. The current research investigates the second alternative through a specific case study as an example. The method comprises adding two new tunnels to an existing twin roadway tunnels. The investigated problem considers the new tunnels to be added vertically or horizontally. The influence of the new tunnel construction on the existing tunnels is investigated considering both the variation of relative position and spacing distance in a parametric study context. Several numerical models are employed to check the construction sequence and the tunnelling safety. These models are used to evaluate the induced stresses in surrounding ground for two different soil types, straining actions in tunnels’ liner and deformations of both ground and liner. The result demonstration shows how to find out the minimum practical and safe spacing distance between the driven new tunnels and the existing ones without the need for the relatively expensive soil strengthening techniques. 相似文献
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地铁开挖和衬砌之后衬砌背后的空区和因其未填实而导致土层破坏,破坏产生的土体松散甚至发展到地面,是影响地面交通和建筑物安全的重大隐患。地铁开挖时,掌子面前方的岩土分界线、含水层的预报,是保证施工安全的重要工作。笔者采用陆地声纳法进行探查工作,取得了直观的效果。在北京通州地铁6号线穿过京哈（北京-哈尔滨）铁路下方的剖面和沿隧道拱顶正上方设置的长60 m的剖面上,可以看到有3处长2 m左右的空区,上方土体已发生松动。在南京4号线某段沿隧道拱顶顶正上方的一条剖面上50 m长度内就发现了9处衬砌背后空区及土体松动区,都诱发了上方土体的松动,松动埋深为8 m,其中有5处土体松动已达到沥青路面下。开挖时出现坍方的一段剖面,虽然坍体仅达地面下约4 m的黏土层,但坍体旁的土体已松动达到沥青路面之下。 相似文献
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通过在拟开掘隧道沿线的专门勘探平洞和煤矿巷道中进行的γ辐射剂量率(225组数据)和环境氡浓度(96个数据)测量,评价和研究该区未来隧道放射性辐射环境。这些平洞和巷道均穿越了(或低于)拟开掘隧洞的底部,基本上揭露了比选隧洞可能穿越的地层岩性。结果表明,在该区煤系地层和侏罗系砂岩交接带可能会出现环境γ辐射照射剂量超标现象,在上述交接带以及含土碎石分布区,有可能出现环境氡浓度超标现象。在选线和施工过程中应引起重视。 相似文献
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近间距大直径公路盾构隧道施工相互影响分析 总被引：1，自引：0，他引：1
结合一外径11.36 m、近距段净距4.0～5.7 m的上海某公路盾构隧道土体和管片位移及应变的监测成果,就后建隧道施工对先建隧道的影响进行了分析。分析结果表明,盾构的推进使隧道间土体朝掘进方向和已建隧道方向侧移,沿深度的最大侧移量发生在隧道中心深度以上0.2D（D为隧道外径）左右;盾尾到达及管片脱出注浆工况阶段,隧道间土体及已建隧道临近面上拱腰处的侧移量达到最大;已建隧道管片呈现上部内敛、下部外扩的变形形态,且临近后建隧道面变形值较大。 相似文献
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基坑开挖对临近地铁隧道影响的两阶段分析方法 总被引：10，自引：0，他引：10
城市高层建筑施工中进行基坑开挖必然引起周围地层移动,从而造成临近地铁隧道纵向不均匀沉降,最终对地铁正常运营产生严重影响。针对目前该领域存在的三维有限元建模复杂及计算耗时的缺点,考虑基坑开挖引起的坑底和四周坑壁土体同时卸荷产生的影响,提出了基坑开挖对临近地铁隧道纵向变形影响的两阶段分析方法。首先计算基坑开挖作用在地铁隧道上的附加荷载,然后基于Winkler地基模型建立地铁隧道纵向变形影响的基本微分方程,根据Galerkin方法将该方程转换为一维有限元方程进行计算,同时研究了不同隧道埋深、距离基坑开挖现场远近、不同地基土质和不同隧道外径等因素对隧道纵向变形的影响。结合大型三维有限元数值模拟以及现场实测数据将计算结果进行了对比,得到较好的一致性。成果可为合理制定基坑开挖对临近地铁隧道的保护措施提供一定的理论依据 相似文献
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Performance of Mortar and Chemical Grout Injection into Surrounding Soil When Slurry Pipe-jacking Method is Used 总被引：1，自引：0，他引：1
Hideki Shimada Takashi Sasaoka Saeid Khazaei Yasuhiro Yoshida Kikuo Matsui 《Geotechnical and Geological Engineering》2006,24(1):57-77
Small-diameter shallow tunnels are often being built by using the slurry pipe-jacking method. This system involves the pushing
or thrusting of a drivage machine and concrete pipes into the ground. Chemical grout injection into the surrounding soil around
the tunnel is carried out after the drivage and pushing processes are finished. The purpose of the chemical grout injection
is to maintain permanent stability of the surrounding soil. However, the behavior of the chemical grouting material in the
surrounding soil around the tunnel and the amount of optimum injection is not clearly understood. From these points of view,
this paper discusses the performance of the chemical grouting material, when it is injected into the surrounding soil around
the tunnel, by means of 2-D Eulerian–Lagrangian seepage analysis. Moreover, the effectiveness of the chemical grout injection
was evaluated by using the non-linear finite element method. This investigation show when the range of the grouted zone is
designed; it is necessary that the relationship between Young’s modulus of the soil/grouted zone and the confining stress
be taken into consideration in order to establish effective, economical and safe chemical grout injection system. Understanding
the performance of the seepage/dispersion behavior of the chemical grout and the characteristics of soil/ grouted zone is
also important. 相似文献
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软土在低水力坡降下的渗流会偏离达西定律,即为非达西渗流模式。假设孔隙水渗透服从指数渗流模式,采用镜像法原理推导了浅埋单孔和双孔圆形隧道非达西渗流场的解析解。结合算例,对浅埋圆形隧道非达西渗流解析解与达西渗流解析解进行了对比分析与验证,并对非达西渗流指数、隧道周围土体与衬砌渗流系数比值对隧道渗流场的影响进行了讨论。结果表明：非达西渗流指数、渗流系数比值对隧道渗流量和周围土体孔压均有较大的影响;随着渗流指数逐渐增大,土体内水头损失加快,隧道周围土体孔压及渗流量逐渐减小;随着土体与衬砌渗流系数比值逐渐增大,衬砌排水能力增强,隧道渗流量逐渐增大,隧道周围土体孔压减小更大。 相似文献
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One of the more promising techniques in soft ground tunneling through urbanized areas is the use of artificially frozen ground for temporary tunnel support. This paper describes the general design considerations involved in the ground freezing method. Various factors are discussed which influence the selection of the freezing temperature, the thickness of the frozen zones and the spacing of the freeze pipes. The time required to achieve freezing is discussed in addition to the amount and rate of frost heave caused by the freezing.
To illustrate the applicability of the freezing method, various considerations in the design of an 8-ft. diameter tunnel in upstate New York, a 75-ft. diameter tunnel in Georgia, and a 12 1/2-ft. diameter tunnel in Washington, D.C. are discussed. All three of the tunnels were to pass immediately beneath mainline railroad tracks. A laboratory testing program was implemented to determine the effects of the repetitive train loads on the zone of frozen soil around the tunnel perimeter. Stress-controlled repeated load triaxial tests were performed on both undisturbed and remolded samples frozen from temperatures of −7°C for the New York tunnel to −10°C for the Atlanta and Washington tunnels. Static testing consisted of both quick triaxial tests and creep tests on frozen samples of the various soil types.
It was found that there was little difference between the cumulative strain response from repeated load tests and static tests for the low frequencies investigated (one-quarter to one-half cycles per minute). Hyperbolic stress—strain functions were developed to simulate the stress—strain relationship for various cumulative loading times.
The stresses and strains in the frozen soil tunnel configuration were computed by the finite element method, using both linear and hyperbolic stress—strain functions. Tangent modulus values were varied to reflect the decreasing modulus with increasing loading time. The analyses indicated that zones of frozen soil of approximately 3 ft. thick were required for both the New York and Washington tunnels. However, high tensile stresses were calculated for the Atlanta tunnel, precluding the use of the freezing method. 相似文献