三峡库区云阳新城水平层状岩体高边坡变形破坏主要控制因素

本文对三峡库区云阳新城一些高边坡的勘察成果进行了总结,目的在于了解云阳新城区近水平岩层条件下边坡变形破坏的型式、主要控制因素及支护要点。结果表明,云阳新城高边坡普遍存在表层剥落现象,含膨胀性矿物(主要是伊利石和绿泥石)的泥质岩较快速风化作用是造成边坡表层剥落式渐进性破坏的主要原因;沿卸荷裂隙与泥化夹层的崩滑是边坡失稳的主要型式,但边坡之间崩滑失稳的程度存在较大差异,一些边坡存在相对较为强烈的卸荷及边坡失稳问题,主要归因于其存在与边坡近于平行的构造裂隙。认为及时进行护坡并在工程设计中考虑结构面的存在型式是边坡防护的重点。     

Jurassic Dextral and Cretaceous Sinistral Movements Along the Hida Marginal Belt

The Hida marginal belt (HMB), which consists of various kinds of fault-bound blocks, is located between the continental massif of the Hida belt and the Mesozoic accretionary complex of the Mino belt in Central Japan. Detailed field investigation reveals that the HMB had grown through the two different movements, i.e., Jurassic dextral and Cretaceous sinistral movements. The Jurassic dextral ductile shear zones run in the southern marginal part of the Hida belt and the northern part of the HMB, whereas the Cretaceous sinistral cataclastic shear zones occur in the southern part of the HMB and the northern marginal part of the Mino belt. Geologic map and field evidence seem to suggest that the Jurassic dextral movement form the fault-bound blocks of the HMB to form the basic structure of the Hida marginal belt, i.e., formation of the ‘proto-HMB.’ Following the dextral movement, the sinistral one restructured the ‘proto-HMB’ to complete the present feature of the Hida marginal belt. The Cretaceous sinistral movement might result in the sinistral collision between the proto-HMB and the Mino belt.     

Spatial probabilistic modeling of slope failure using an integrated GIS Monte Carlo simulation approach

Spatial probabilistic modeling of slope failure using a combined Geographic Information System (GIS), infinite-slope stability model and Monte Carlo simulation approach is proposed and applied in the landslide-prone area of Sasebo city, southern Japan. A digital elevation model (DEM) for the study area has been created at a scale of 1/2500. Calculated results of slope angle and slope aspect derived from the DEM are discussed. Through the spatial interpolation of the identified stream network, the thickness distribution of the colluvium above Tertiary strata is determined with precision. Finally, by integrating an infinite-slope stability model and Monte Carlo simulation with GIS, and applying spatial processing, a slope failure probability distribution map is obtained for the case of both low and high water levels.     

Reliability based risk index for the design of reinforced earth structures

The design methods currently used for earth reinforcement are mostly based on deterministic properties of both the soil and the construction materials used. Nowadays, however, the general trend is designing at a specific degree of reliability. This is even more true where the raw data such as soil properties exhibit significant variation. Deterministic solutions, in this case, may not suffice. Therefore, this paper will attempt to use probabilistic formulations thereby modifying the existing design procedure of reinforced earth retaining walls to account for uncertainties and variabilities. Through a first order Taylor's series expansion about the mean, the mean and variance of the strip reinforcing components, namely width and length, are derived in terms of the variations in the soil properties. Design charts that enable estimation of both mean and variance are developed to avoid extensive partial differentiation involved in the computations. Using appropriate probability distributions along with the mean and variance, the final design outputs are determined for a selected failure probability by introducing what is refered to as 'risk index'. The results indicate that the risk index increases with an increase in the coefficient of variations and a decrease in failure probability. Furthermore, it is shown that in some cases, depending on the variabilities of the soil properties, the classical design technique produced a relatively high failure probability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contrasting metamorphic evolution of metasedimentary rocks from the Çine and Selimiye nappes in the Anatolide belt, western Turkey

Abstract P–T conditions, mineral isograds, the relation of the latter to foliation planes and kinematic indicators are used to elucidate the tectonic nature and evolution of a shear zone in an orogen exhumed from mid‐crustal depths in western Turkey. Furthermore, we discuss whether simple monometamorphic fabrics of rock units from different nappes result from one single orogeny or are related to different orogenies. Metasedimentary rocks from the Çine and Selimiye nappes at the southern rim of the Anatolide belt of western Turkey record different metamorphic evolutions. The Eocene Selimiye shear zone separates both nappes. Metasedimentary rocks from the Çine nappe underneath the Selimiye shear zone record maximum P–T conditions of about 7 kbar and >550 °C. Metasedimentary rocks from the overlying Selimiye nappe have maximum P–T conditions of 4 kbar and c. 525 °C near the base of the nappe. Kinematic indicators in both nappes are related to movement on the Selimiye shear zone and consistently show a top‐S shear sense. Metamorphic grade in the Selimiye nappe decreases structurally upwards as indicated by mineral isograds defining the garnet‐chlorite zone at the base, the chloritoid‐biotite zone and the biotite‐chlorite zone at the top of the nappe. The mineral isograds in the Selimiye nappe run parallel to the regional S_R foliation, parallel the Selimiye shear zone and indicate that the Selimiye shear zone formed during this prograde greenschist to lower amphibolite facies metamorphic event but remained active after the peak of metamorphism. ⁴⁰Ar/³⁹Ar mica ages and the tectonometamorphic relationship with the Eocene Cyclades–Menderes thrust, which occurs above the Selimiye nappe in the study area, suggests an Eocene age of metamorphism in the Selimiye nappe. Metasedimentary rocks of the Çine nappe 20–30 km north of the Selimiye shear zone record maximum P–T conditions of 8–11 kbar and 600–650 °C. An age of about 550 Ma is indicated for amphibolite facies metamorphism and associated top‐N shear in the orthogneiss of the Çine nappe. Our study shows that simple monophase tectonometamorphic fabrics do not always indicate a simple orogenic development of a nappe stack. Preservation in some areas and complete overprinting of those fabrics in other areas apparently occur very heterogeneously.     

新疆某水利枢纽工程软弱结构面抗剪强度参数的试验研究

某水利枢纽工程位于伊犁地区,影响工程的主要问题为坝基岩体软弱结构面和断层的抗滑稳定问题。根据工程实际条件和软弱夹层特性,采取现场断层软弱结构面试验和室内模拟试验相结合,获得软弱夹层的抗剪参数。实践证明,把两种方法结合起来的试验成果可靠,尤其对一些不具备进行现场大型岩体软弱夹层抗剪试验的工程,采用室内中型直剪仪进 行剪切试验具有实用意义。     

重塑非饱和粘土抗剪强度参数与饱和度的关系研究

土的饱和度是基于水分状态和密度状态的一个衍生变量。存在因应水分状态变化和因应密度状态变化的两类饱和度变化过程。根据23组不同水分状态和密度状态的UU三轴压缩试验结果,讨论了重塑非饱和粘性土抗剪强度参数与饱和度的关系。数据分析表明:粘聚力与水分状态相关的饱和度的关系是强非线性的,与密度状态相关的饱和度的关系是准线性的。内摩擦角与水分状态相关的饱和度的关系是强非线性的,与密度状态相关的饱和度的关系是弱非线性的。     

岩质边坡稳定性分析的探讨

通过最大剪应力等值线来确定边坡的滑动面,并与其结构面抗剪强度相比较,给出了确定边坡的稳定系数的方法。     

地震前地表重力场变化的一种可能解释——应力-损伤耦合效应

文中运用损伤力学研究方法 ,提出孕震过程中引起地壳破坏的应力 -损伤耦合效应。利用应变等效性假设 ,推导了地壳体的应力 -损伤耦合效应与地表重力变化之间的理论关系。根据岩石力学实验的不同加载途径 ,模拟了 1976年唐山 7 8级地震和 2 0 0 1年昆仑山口西 8 1级地震重力演化的不同特征 ,结果与实际情况符合较好 ,表明应力 -损伤耦合效应可以作为地震前地壳重力变化的一种物理解释