【作者】 徐浩；

【导师】 王成；

【作者基本信息】 重庆交通大学 ， 桥梁与隧道工程， 2010， 硕士

【摘要】 岩土工程三个主要的研究对象是边坡、地基与隧洞,前两者均可进行岩土的稳定性分析,惟有隧洞围岩至今没有真正意义上的稳定性分析,还处于经验设计阶段,这大大影响了隧洞工程的设计水平。当前关于隧洞近接桩基的稳定性问题还没有一个较好的分析方法,也没有提出合适的评判指标,在设计过程中主要是根据已有的经验对桩与隧洞的距离提出一些控制原则。本论文针对有限元强度折减法在隧洞近接桩基稳定性分析与设计中的应用以及隧洞位移释放系数进行了较详细的研究。论文的主要工作与创新点如下:①通过研究岩体强度、桩基荷载、桩与隧洞距离、桩的埋深等各种影响因素对桩基荷载作用下隧洞稳定性的影响,计算表明桩基与隧道影响的临界距离为距隧道侧墙约1倍洞径。当桩与隧道距离在临界距离以内时桩基荷载的变化对隧道安全系数有较大影响,荷载增大一倍,安全系数约减小1/4。隧洞围岩岩体强度对围岩安全系数影响较大,本文围岩强度从砂岩降低至泥岩时,围岩的安全系数降低1/4。②随着掌子面推进,对于围岩位移释放系数影响程度较大的是岩体的强度参数(粘聚力、内摩擦角)和初始应力状态(泊松比),变形模量对围岩位移释放系数的影响很小,影响量在1%左右。最大影响量是泊松比对边墙的影响,达到了20%以上,但其对拱顶和底部的影响相对较小;在强度参数的单因素分析中,当其达到一定量值时再继续增大,围岩的变形和位移释放比都会趋于一个定值。围岩的位移释放主要集中在监控断面0.5倍洞径范围内,占到了总位移的70%~80%,尤其是当掌子面通过监控断面0.5倍洞径时,位移释放量占到总位移的50%~60%。③当围岩释放系数大于60%时,相同释放系数下随着围岩强度的降低,桩基荷载下隧道的安全系数迅速减小,当为Ⅴ级围岩时,隧道的安全系数小于1,说明在强度较低的围岩上不宜修建桩基础。而强度较高的围岩安全系数较高,有较大的安全储备。更多还原

【Abstract】 Slop foundation and tunnel are the three main research objects of the Geotechnical Engineering. The stability analysis of soil can be carried out in the former two, and only the stability of tunnel rock mass can not be analyzed precisely until now. It is still based on some experiences, which restrictes the design of tunnel.There is no better method of analysis about the stability of tunnel under pile loads and the judge is not offered current.During the design process ,people mainly base on existing experience of distance between pile and tunnel and propose some control principles.The application of strength reduction FEM in the stability analysis of tunnel under pile loads and design and displacement release factor of tunnel were studied in detail in this thesis.Main tasks and key innovations are follows:①The influence factors of stability of tunnel by pile loading such as strength of rock mass, pile load, distance between pile and tunnels, depth of pile were studied. Through analyzing the calculation result of safety factors,we found critical distance is one times the diameter of the tunnel from the side wall.When the distance of pile and tunnel Within the critical distance,load of pile has greatly influence on safety factor of tunnel.when the load increases twice, safety factor will reduce about 1/4. Rock mass strength of surrounding rock has greatly influence on safety factor of surrounding rock.Roce mass was reduced from sandstone to shale, safety factor of surrounding rock will reduce 1/4.②With the heading propeling,rock mass strength parameters(cohesion、internal friction angle) and the initial stress state(poisson’s ratio) has greatly influence on the release factor of surrounding rock displacement. Deformation modulus has little effect to the release factor of surrounding rock displacement,affect the volume of about 1%.The greatest impact volume is Poisson’s ratio effects on the side walls, reaching more than 20%, but its impact on the vault and the bottom will become relatively small.In the strength parameters of the single-factor analysis, when it reaches a certain value and continues to increase again , the surrounding rock deformation and displacement will tend to release more than a fixed value. the release factor of surrounding rock displacement focused o n monitoring section 0.5D, the accounting for the total displacement of 70% to 80%. Especially when the working face by the monitoring section 0.5D, displacement release for the total displacement of 50% to 60%.③When the rock releasing factor of more than 60%,under the same releasing factor, with the reduction of rock strength, safety factor of tunnel will reduce rapidly.As for the V grade rock, the tunnel’s safety factor is less than 1.So when the strength of surrounding rock is lower,the construction of pile foundation should not be built.Intensity of a high rock safety factor high, greater security reserve.更多还原