【作者】 谭志宏；

【导师】 唐春安；

【作者基本信息】 东北大学 ， 工程力学， 2008， 博士

【摘要】 岩溶灾害是也是交通建设主要工程地质问题之一。而空洞是岩土工程稳定性影响中的一个重要因素,其表现形式以溶洞、巷道最为常见。岩溶区含空洞路(桥)基础和隧道在外部载荷和环境作用下会造成自身岩体强度的弱化,最终可能导致工程失稳破坏。空洞在其破坏过程中的作用和影响是一个及其复杂又具有挑战的研究课题。而这类研究所面对的对象尺度都比较大,如果采用常规的物理试验需要耗费大量的人力和财力,并且实验过程中也可能会受到其它因素的干扰而导致实验失败。而采用理论计算研究的话,又常常需要对模型进行大量的简化处理,计算结果与实际情况有时存在较大偏差。强度折减法已被广泛运用于岩土工程稳定性的研究分析,既能较为真实的反映实际情况,又更经济、有效。本文在路桥工程稳定性分析过程中首次采用距跨比代替距离作为稳定性分析评价的指标之一,使分析结果更加客观；而非均匀性是岩石的一个重要特性,本文在强度折减分析过程中引入了岩石的非均匀性,使分析结果更能反应实际情况；本文还将拉伸破坏准则引入模型的稳定性分析,采用带有拉伸破坏的修正摩尔-库伦准则作为临界强度判据,使所得安全系数为考虑了压剪和拉伸的一个综合安全储备系数。目前,工程中空洞影响的研究主要集中在具体工程实例中的分析以及处理方法的讨论上,对空洞影响进行系统性研究的不多。本文在前人的基础上,总结了岩溶地区路桥工程稳定性的影响因素以及评价方法,详细介绍了RFPA有限元强度折减方法的基本原理、强度准则、本构关系以及失稳判据和安全系数的定义。采用RFPA强度折减版对路桥工程中空洞对围岩稳定性的影响进行了研究。论文的主要从以下几个方面分析了空洞对稳定性的影响：(1)不同围岩均质度条件下,空洞对路、桥基以及隧道围岩稳定性影响的规律性；(2)不同空洞断面形式下(水平椭圆、圆形、竖直椭圆),空洞对路、桥基以及隧道围岩稳定性影响的规律性；(3)空洞不同洞径大小及分布情况(对于路、桥基来说不同的埋深,对于隧道来说包括不同远近以及分布位置)对路桥工程围岩稳定性响的规律性；(4)以崇遵高速公路建设中所遇到的路、桥基础及隧道岩溶问题为工程依托,对实际工程中空洞的影响进行分析,研究隐伏空洞对围岩应力、位移的影响特性。通过以上四个方面的研究发现：1.岩石的非均匀性对路桥工程的稳定性影响较大。对于岩性较差,风化程度较高,比较破碎的岩体而言,岩体的安全储备系数对均匀性的变化更加敏感。在相同岩性条件下,随着岩体均匀性的增大,安全系数增大,岩体的稳定性也相应提高。路基下应变拱和路、桥基下弱应力区的监测对于判断其稳定性具有重要的意义。隧道顶板的稳定性受均匀性影响较小。2.对于不同空洞的断面形式,路桥工程的稳定性不同。横向近椭圆(长轴方向与最大主应力方向垂直)空洞对围岩稳定性的影响最大,竖向近椭圆空洞的影响次之,圆形空洞的影响最小。空洞跨度对于工程稳定性的影响要远大于空洞深度的影响。路基顶板的塌陷是由于顶板两侧的拉应力过大而产生的拉破坏,桥基的塌陷则是由于顶板上方的载荷过大,超过顶板抗压、抗剪力而产生的压剪破坏。3.空洞洞径大小和距跨比对隧道稳定性有显著影响。随着空洞洞径的增大和距跨比的增加,隧道的安全系数随之增大。当空洞洞径小于隧道洞径的时候,一般都是隧道先发生破坏。随着洞径的增大,破坏逐渐向空洞转移,特别是在空洞位于隧道底部时,甚至会发生孔洞将隧道破坏完全屏蔽,这时主要应注意隧道底部的变形。4.对路(桥)基础而言,随着空洞埋深的增大,安全系数逐渐增大,基础稳定性增强；在相同距跨比下,随着空洞洞径的增大,安全系数明显下降,基础稳定性减弱。5.对于隧道而言,空洞与隧道距离对稳定性的影响要大于洞径大小的影响；对于路(桥)基而言,空洞洞径的变化对稳定性的影响要大于空洞到路(桥)基距离变化的影响。更多还原

【Abstract】 Disaster caused by the cave is one of the primary matter for the road project at Karst area. At the Karst area, rock strength of wall rock of tunnel and bedrock of the road and bridge could be weakened by the effect of the environment and load. The weakening of the rock could make the project failure. The influence of the cave on the project during the failure process is a complex and challenged problem. Because the scale of research object is great, the routine physical experiment need much resource and manpower, the experimental result can be disturbed by many reasons, the experiment also would be unsuccessful sometimes. The rock considered as the homogeneous medium and calculation model need too much predigest when we used the academic calculation. But the inhomogeneous is a important character of the rock, the calculation result may be different with the real fact. The strength reduce method is used widely for stability analysis in rock project now. The analysis result accord with the reality. It is cheaper and more effective too. Because the distance and diameter are variable, the rule got by them is unsure. So the distance diameter ratio (DDR) is used to replace the distance as one of estimate standard of the stability analysis in this thesis. The result will be more impersonal. The rock is considered as the homogeneous medium in the past stability analysis, but the inhomogeneous is a very important character for the rock. Inhomogeneous of rock is considered in thesis to make the result more fit for the fact. The tension rule is considered in the stability model too. The results got in the thesis is a integrative safety factor consider the shear stress, compressive stress and tension stress.The stability research of the cave is focused on idiographic project for most researcher. Some research on how to deal with the cave. Only a little people research on the influence rule of the cave, near the rock project. The rule is important for the people to consult in other project. Based on the research in past, the thesis sum up the influence factor and analysis method of stability of the road project at Karst area first. The rationale, strength rule, constitutive law and failure criterion of the RFPA-SRM is introduced then. At last, RFPA-SRM is used to analyse the stability influence rule of the cave near the road project. To make the result reflect truer, inhomogeneous of the rock is considered in the model. The content of the thesis as follows:(1)Influence rule of the cave on stability of the wall rock of tunnel and bedrock of the road and bridge with different homogeneousness of the rock is studied in the thesis; (2)analyse the stability variety rule of road project when the section shape of the cave is different(circle, ellipse in horizontal, ellipse in vertical); (3)analyse the stability variety rule of road project when the diameter and location of the cave is different(for the road and bridge, location means the distant between floor and cave, for the tunnel, location means the distant between tunnel and cave); (4)based on the problem caused by the cave in chong-zun highway building process, studied the influence of the cave on stress and deformation of the wall rock in true project.By the research on the influence of the cave, the results shows that:1. Influence of the rock inhomogeneousness is obvious for the stability of road project. For rock of the bad lithology or high weathering, the safety factor of the rock is more impressible to the inhomogeneous of the rock. The stability and the safety factor of the project increase with the homogeneousness of the rock increase when other conditions are the same. It’s very significative for the stability estimate to inspect the strain cove of the road and feebleness stress zone. For the tunnel, stability of the tunnel roof change less when the rock homogeneousness change.2. The stability of road project is different when the section shape is changed. For the stability of the project, the influence of cave with the section of ellipse in horizontal (long axis apeak the max. principal stress way) is the most, influence of the circle is the least. change of the cave’s span is more influential than the change of the cave’s depth. The bedrock of the road and bridge upon the cave will be damaged easily when the span is greater than the distance between cave and bedrock surface. The failure of the roadbed is caused by the big tension, the failure of the bridge bedrock is caused by the big compressive stress.3. The change of the cave’s diameter and distance diameter ratio (DDR) is very influential for the stability of tunnel. The safety factor increase with the increase of the cave’s diameter and DDR. For the stability of the tunnel, influence of the cave’s location is not changeless. When the diameter of the cave less than the tunnel’s span, tunnel failure at first. The damage transfers gradually to the rock near the cave when the diameter of the cave increase. Specially to the cave under the tunnel, there are little damage in the rock around tunnel while cave failure when the diameter of cave bigger than the tunnel’s.4. For the road and bridge, the bedrock’s safety factor and stability increase with the increase of cave’s DDR when the diameter is changeless, the safety factor and stability of bedrock decrease with the increase of cave’s diameter when DDR is changeless.5. For the wall rock of tunnel, distance between cave and tunnel is more influential to the stability of wall rock than diameter of the cave. For the bedrock of road and bridge, diameter of cave is more influential to the stability of bedrock than distance between cave and the bedrock surface.更多还原