Morphological Characteristics of Till Formations in Relation with Mechanical Parameters

The study of landslides stability on mountain slopes can become very difficult when materials in movement are heterogeneous: it is a current problem with the old glacial till formations presently under study (Aspe Valley, Pyrénées, France). Analysis of slope stability using numerical models necessitates accurate data about mechanical and physical properties. Because tills are very heterogeneous, a large sample is necessary but, unfortunately, data acquisition costs a lot of time and money. Therefore, we would like to estimate mechanical data from correlated parameters that are easier to acquire (morphological parameters using image analysis). Observations in the field and previous mechanical results in the laboratory have shown that differences between the behavior of tills seem to be related not only to their 3D structure but also to the morphological and petrographical characteristics of their components. The aim of this paper is first to illustrate how to classify the till formations textural and petrographical characteristics at the sample scales; these classifications are based on the distributions of size, shape of their constitutive elements (blocks, matrix, etc.). Significant statistical results are available by applying image analysis methods based on mathematical morphology. Next we show how these characteristics are related to the mechanical characteristics (friction angle, cohesion). Six specific till formations were collected, and we establish the relation between the effective internal angle of friction and the elongation factor.     

老顶岩块端角摩擦系数和挤压系数实验研究

通过岩块实验、相似模拟和计算模拟, 研究了采场老顶岩块端角摩擦和端角挤压特性。 得出老顶岩块端角摩擦角为岩石残余摩擦角, 摩擦系数确定为 0 . 5; 端角挤压强度受弱面的影响明显且具有规律性, 端角挤压系数确定为 0. 4     

五层地下室深基坑边坡支护的设计与施工

广州市华标涛景湾二期工程建筑物设计5层地下室，基坑深度大，周围环境复杂，在基坑边坡支护结构设计与施工过程中，对土层与岩层区别对待，经过精心设计与严格施工，取得较好的实效。介绍了该基坑边坡支护设计及施工要点。     

四川汶川Ms 8 级地震触发的典型滑坡的风险指标反演

2008年汶川大地震触发了数以万计的崩塌和滑坡,特别是沿发震断裂分布一系列大型的高速远程滑坡。为了探索地震诱发大型高速远程滑坡运动速度的反演方法,以汶川大地震典型高速远程滑坡为例,在野外调查和室内分析的基础上,结合前人的研究成果,对沿映秀－北川断裂展布的5个典型滑坡的速度进行了反演和计算。结果表明,5个滑坡的最大速度均大于50m/s,其中大光包滑坡速度最大,其下部滑体的最大速度约为300m/s,上部滑体凌空飞行的初速度高达165.6 m/s。同时,对上述滑坡的视摩擦系数进行了计算,4个滑坡的视摩擦系数介于0.16~0.4之间。这一研究的目的在于为类似地区地震滑坡的速度、最大位移量的预测和风险评估提供基础数据,对于类似地区的防灾减灾具有一定的参考价值。     

关于将重晶石列为战略性矿产的原则分析

战略性矿产是国家矿产资源宏观调控和监督管理的重点对象,加强战略性矿产研究、明确自身比较优势和薄弱环节,对于完善全国矿产资源规划中的战略性矿产目录、为国家相关产业政策制定提供借鉴参考具有重要意义.本文以重晶石为研究对象,运用文献集采法、比较研究法,从重晶石在美国的产业发展地位、资源不可替代性、对国际市场的影响力等三方面分...     

青藏铁路沿线地表和路基表面热力学模式(Ⅰ):物理过程与实验方案

路基表面的热状况具有时空分布的非均匀性,筑建在冻土区的路基,其下伏冻土层对上边界非均匀热强迫的响应,会引起冻土层的冻胀、融沉非均匀变化,进而造成路基的变形失稳.因此,了解路基表面热状况的时空变化规律对监测和防治路基冻融病害、保证路基稳定性具有重要意义.鉴于此,从热力学研究角度出发,以气候影响因子-大气辐射传输-地气交接面辐射特性-地气间热量交换为研究主线,基于能量守恒原则,建立针对青藏铁路沿线地表、路基上表面和路基左右边坡表面的普适性热力学数值模式,用于高海拔青藏铁路全线的任意坡度和走向的路基表面热状况的定量化研究与应用.     

外套框架加层结构利用摩擦和消能装置试验及构造措施研究

本文提出了在外套框架加层结构中采用摩擦阻尼器和砂垫层作为减震装置，进行增设摩擦和消能的加层结构模型的振动台试验，结果表明，采用摩擦和消能装置能有效地减小加层结构的地震反应。在此基础上，对采用摩擦和消能装置加层结构的构造措施进行了研究。     

充气锚杆极限承载力计算方法

为研究充气锚杆极限承载力计算方法,在模型试验基础上,探讨充气锚杆抗拔过程中的受力特征与破坏形式,分析锚杆荷载-位移曲线变化特征。基于圆孔扩张理论,通过简化力学模型,推导充气锚杆侧阻力与端阻力计算公式,将理论公式计算值与试验成果进行比较。研究结果表明：(1) 采用球孔扩张理论可以较好地描述膨胀体端部对土体产生的弹性、塑性变形力学机制,估算端阻力值。充气膨胀压力对土体的挤压膨胀作用大大增加了锚杆的侧阻力。(2) 极限承载力理论公式计算值与抗拔试验值基本吻合,验证了极限承载理论计算公式的正确性。(3) 通过与螺旋锚杆相比,充气锚杆的承载力约为单锚片螺旋锚杆的4.3倍,约为双锚片螺旋锚杆的1.9倍,充气锚杆的承载能力优势明显。     

考虑负摩阻力的刚性桩复合地基工作性状分析

以带褥垫层的刚性桩复合地基为研究对象,在考虑桩体负摩阻力作用的条件下,讨论了桩身侧摩阻力分布状况,建议了侧摩阻力线性简化计算模型。分析了带褥垫层刚性桩复合地基桩体与褥垫层的相互作用,计算了桩顶对褥垫层的刺入量。推导了桩体位移微分方程,并根据方程,同时结合中性面的定义,给出了求解中性面深度比的计算方法,讨论了其影响因素及取值范围。算例显示,按该方法计算的结果符合工程经验。     

Residual Currents Through the Dover Strait Measured by H.F. Radar

Residual (i.e. non-tidal) components of flow in the Dover Straits are determined from measurements recorded by the OSCR H.F. Radar system. The data are divided into 10 monthly sets, obtained from 5 months of dual radar deployments on the English side of the Straits and a corresponding 5 months from the French side. For each of these sets the tidal component was removed by subtracting constituents derived from separate (monthly) harmonic analyses.In each deployment, surface currents were measured at 700 locations at 20-min intervals, providing spatial resolution on a grid as fine as 660 m. This fine spatial resolution reveals distinct patterns of monthly-mean residual circulations never previously recognized. In particular, a residual gyre is shown to be a dominating feature along the French side, with currents exceeding 20 cm s^-1 and a diameter of 20 km. The previous obscurity of this feature may be attributable to the large (> 1·5 m s^-1) and strongly spatially variable tidal currents. In these conditions, tidal advection will rapidly smear any surface signature obtained from satellite observations. Likewise, fine resolution (grid spacings of an order of 1 km) is required to reproduce these gyre dynamics in numerical models.The time-varying residual currents were correlated with wind recordings. Significant correlations were obtained for an 'open-sea' response (as represented by Ekman theory), with the wind-driven surface current veering at angles of up to 45° to the right of the wind direction. This 'open-sea' response is modified close to the coast where the generation of surface gradients force the currents to align with the topography.Larger-scale residual motions were identified from modal analyses. The primary modes, on both sides, involved large-scale flows through the Straits partially correlated with local winds. However for winds aligned approximately north-south, the components of these flows on the English and French sides are in opposition. These modes also revealed large oscillatory motions with periods of between 20 and 40 h.Estimates of net residual flows through the Straits from the radar measurements confirm earlier calculations of the range of variability in this parameter. However the increasing complexity of the flow patterns revealed in this study emphasizes the difficulty in quantifying the long-term net flow.