【作者】 姚裕春；

【导师】 姚令侃；

【作者基本信息】 西南交通大学 ， 防灾减灾工程及防护工程， 2005， 博士

【摘要】 重大工程灾害与防治成为21世纪核心科学问题之一,必须从可持续发展的战略高度研究“重大工程灾害与防治”。国家已把铁路和高等级公路等交通干线建设作为实施西部大开发的重要举措,并已列入国家建设的优先领域。西部地区工程建设条件复杂,生态环境脆弱,环境条件对道路建设严重制约,道路工程对环境影响问题严重,其中道路边坡开挖活动问题尤为突出。由此,研究边坡开挖工程对山区环境影响作用具有重要意义。 我国西部山地环境灾害是地球内外动力耦合作用的产物,边坡开挖对山地环境影响表现为影响了山地动力系统及山地动力系统作用的环境,从而加速山区环境演变和引发山地边坡灾害。 开挖引起的强扰动区范围是工程活动影响山地环境演化进程和评价工程开挖活动对环境影响的一个重要指标。由于开挖坡体在应力松弛情况下,其变形、损伤均是一个逐渐积累的过程,当变形或损伤达到一定程度后,坡体单元结构会发生明显的破坏或损伤发生突变。边坡土体的变形模量是其抗变形能力的一个综合反映,因此进行了基于边坡土体变形模量的损伤分析,提出把引起边坡单元发生损伤突变的围压作为确定强扰动区边界的判别标准,并给出了确定开挖边坡强扰动区范围的方法。 施工时序是一个不断变化的过程,不同的开挖、支挡顺序对边坡岩土体变形有很大的影响,进而影响边坡稳定性。应用离心模型试验定量地分析了不同施工时序对边坡稳定性的影响,并直观地比较了边坡的变形破坏程度。数值计算分析了不同施工时序的作用机理:及时支护程度越高,坡体开挖面剪应力集中程度越低,坡面最大剪应力连通程度越差,从而有利于坡体稳定;及时支护,坡体单元应力历史(应力路径)过程为应力由大逐渐减小至平衡,而开挖完成后再支护(滞后支护)应力变化过程为先急剧降低,发生较大程度的应力松弛,随支护的进行应力逐渐增大至平衡,但最后应力值小于及时支护应力值,即滞后支护造成坡体发生较大的不可恢复损伤,坡体强度参数降低,且坡体开挖面剪应力集中程度大,结果对坡体稳定不利。 坡体开挖及时支护有利于边坡稳定,但对于超高边坡开挖,及时支护由于受下级开挖应力调整影响,上级支护结构受力变大而可能失效。通过数值更多还原

【Abstract】 Disaster and its prevention of large engineering activity become the core scientific project of 21th century, the study of which must be based on the sustainable development. Now the construction of railway and highway has been taken precedence over other national construction in west China. But the environment condition restricts the road construction because of complex geology and fragile environment. So the engineering construction, especially the slope excavation, has a large influence on environment Thus, it’s practicable to study the slope cutting action.The mountain environmental disaster is the results of coupling of earth’s endogenic and exogenic geological process in west China. The slope cutting influences the mountain environment through changing the exogenic system or its environment. The results are that the evolution of mountain environment is accumulated or the mountain disasters are caused.The range of strong disturbed zone due to slope cutting is an important criterion to evaluate the influence degree of slope cutting to environment. The deformation and damage of the cut slope is an accumulation process. After the deformation and damage of slope units accumulates to some magnitude due to stress relaxation, distinct damage of slopes structure will be caused. The deformation modulus is a comprehensive parameter to represent the deformation ability of soil slope. Based on the damage analysis of soil slope, the stress which causes damage variable an abrupt increasing, can be as the criteria to analyze the strong disturbed zone. And the method to analyze the strong disturbed zone is discussed.Different excavation and support sequence have a large effect on the deformation and stability of slope. Based on centrifuge model tests and numerical calculation, (he deformation failure and stress field, due to different excavation and support sequence, are analyzed. The results show that promptly supporting after been cut can reduce the deformation magnitude and improve the stability of slope. The mechanism of promptly support with high stability is that the concentration degree and connection of themaximum shear stress are weak, the stress relaxation are low, and the stress history is better to slope’s stability. In contrast, support after the cutting finished cause the cut slope with large stress relaxation and high damage degree.Timely support to cut slope avails to the slope’s stability. But to the supper high slopes, the up support measures may fail because of overly stress caused by down stages’ excavation. Based on the results of numerical simulation, we suppose temporary support to up stages firstly, and then permanent support after the whole slope been cut. Thus, it can behave the "New Austrian" principle and satisfy the stability with a low cost.Due to fragile environment of mountain area in west China, the slope excavation may not only influence the stability of itself, but also influence the close slope. That is, the close slope may be influenced by the transition of deformation and failure of the cut slope. In the thesis, the transition effect due to part cutting of soil slope is the first time to be studied. The centrifuge model tests of soil slopes with part cutting indicate that three transition types caused because of no support measures taken in time. The first is the whole tensile crack failure under low stability, the second is the arc tensile crack failure under high stability; the third is the shallow collapse failure on the cut face under loose material slope. To engineering practice, we must consider the transition effect for those wreck soil slopes and fragmentary rock slopes, but with little attention to those strong strength soil slopes and integrated rock slopes.The failure of temporary slopes is very common in engineering practice. Rainfall is a key factor to the failure of temporary slopes. The centrifuge model tests indicate that two failure types of soil slope are relevant to different water content, i.e. tensile crack failure occurs under low water content, in contrast, whole failure occurs. There are critical damage variable and the corresponding critical water content, the two failure types of slope can be distinguished by the critical water content.With the increasing of cut degree of slope and support’s delay, the evolution of cut slope will behaves self-organization characteristics. That is, the non-linear relation of deformation and slide force acts, and the slope will fail. The forming process of self-organization is the process of reduction of entropy, or the process of deformation’s regulary degree from low to high. And the forming process of self-organization is studied trough entropy analysis. Then the disaster prevention measures are presented that timely support measures are taken to prevent the forming of self-organization.更多还原