Geomorphology's role in the study of weathering of cultural stone

Great monumental places—Petra, Giza, Angkor, Stonehenge, Tikal, Macchu Picchu, Rapa Nui, to name a few—are links to our cultural past. They evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes. However, as with natural landforms, human constructs are subject to weathering and erosion. Indeed, many of our cultural resources suffer from serious deterioration, some natural, some enhanced by human impact. Groups from the United Nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources, from simple rock art to great temples. Geomorphologists trained in interacting systems, process and response to thresholds, rates of change over time, and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact.Review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering. Because the stone was carved at a known date to a “baseline” or zero-datum level, some of the simplest methods (e.g., assessing surface weathering features or measuring surface recession in the field) provide useful data on weathering rates and processes. Such data are difficult or impossible to obtain in “natural” settings. Cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure (microclimate) and human impact. More sophisticated methods confirm these observations, but also reveal discrepancies between field and laboratory studies. This brings up two important caveats for conservators and geomorphologists. For the conservator, are laboratory and natural setting studies really analogous and useful for assessing stone damage? For the geomorphologist, does cultural stone data have any real relevance to the natural environment? These are questions for future research and debate. In any event, cultural stone weathering studies have been productive for both geomorphologists and conservators. Continued collaboration and communication between the geomorphic, historic preservation, archaeological, and engineering research communities are encouraged.     

浙江省新昌县下山村滑坡地质特征与稳定性评价

本文研究了浙江省新昌县下山村滑坡区地质环境条件,介绍了滑坡地质灾害体的地质结构、形成特征。认为该区地质环境复杂,雨量充沛,地形呈阶梯状;岩层以5个旋回的软硬相间为主,覆盖层为第四纪松散层;滑坡体赋存松散岩类孔隙水和基岩孔隙-裂隙水,滑坡区岩土体遇水后工程地质性质变差,其抗滑、抗软化能力较差。滑坡表现为后缘切层、中-前缘顺层型。文章从滑坡成因类型的形成条件、变形破坏机制和诱发滑坡体失稳的主要因素方面,对滑坡的稳定性作出了基本评价,对其发展变化作出了趋势性预测。认为该滑坡体物质结构复杂,分7（大）层,滑坡有多个滑移带,主滑移面（带）2个,滑坡体厚达60m,降雨是诱发滑坡体失稳的主要原因,该滑坡目前仍以蠕滑为主。     

伯格斯模型参数调试与岩石蠕变特性颗粒流分析

岩石作为地下工程的主要研究对象,其物质组成和所赋存的复杂地质环境使其具有明显的流变特性。基于三维颗粒流程序(PFC3D),采用由开尔文模型和马克斯伟尔模型串联组成的伯格斯（Burgers）流变模型,通过控制变量法,分析了伯格斯模型中弹性系数(Em和Ek)、黏性系数(?m和?k)和摩擦因数f对瞬时强度特性和流变特性的影响;分析得出数值试样的瞬时强度特性主要受马克斯伟尔体弹性系数Em和摩擦因数f影响：弹性模量和单轴抗压强度与Em和f均呈正相关,泊松比与Em呈正相关,与f呈负相关;而流变特性与各参数均呈现负相关性。在此基础上,进行了红页岩分级增量蠕变试验的模拟,通过与室内蠕变试验结果的对比,验证了PFC3D中的伯格斯模型用于岩石蠕变试验模拟的可行性,并将该方法用于分级增量循环加卸载蠕变试验和三轴蠕变试验数值研究。该研究内容是利用离散单元法研究岩石流变特性的一种新的尝试。     

Temporal and spatial variation of infilling processes in a landslide scar in a steep mountainous region,Japan

The duration of the soil‐depth recovery needed for reoccurrence of shallow colluvial landslides at a given site in humid regions is much longer than the return period of rainfall needed to generate sufficient pore water pressure to initiate a landslide. Knowledge of the rate of change in soil depth in landslide scars is therefore necessary to evaluate return intervals of landslides. Spatial variation in sediment transport at the Kumanodaira landslide scar in central Japan was investigated by field observations. Spatial distribution of the rate of change in soil depth was estimated using sediment transport data and geographic information system (GIS) analysis. Observations revealed that the timing of sediment transport differed for shallow and deep soil layers. Near‐surface sediment transport (mostly dry ravel and some shallow soil creep at depths ≤0·05 m) measured in sediment traps was active in winter and early spring and was affected by freezing–thawing; soil creep of subsoil (i.e. >0·05 m), monitored by strain probes, was active in summer and autumn when precipitation was abundant. Near‐surface sediment flux was estimated by a power law function of slope gradient. Deeper soil creep was more affected by relative location to the landslide scar, which influences soil depth, than by slope gradient. Our study indicated that the rate of soil‐depth recovery is high just below the head scarp of the landslide. Abrupt changes in the longitudinal slope topography immediately above, within and just below the head scarp became smoother with time due to degradation proximate to the landslide head scarp and flanks, as well as aggradation just below the head scarp. Copyright © 2014 John Wiley & Sons, Ltd.     

坝区岩体蠕变参数解析-智能反演方法及其工程应用

岩体蠕变参数是岩土工程设计必不可少的重要资料,为准确确定岩体的蠕变力学参数,综合考虑解析反演法和智能反演法的优点,将这两种反演方法耦合,建立了岩体蠕变参数的解析-智能反演方法,将这种方法应用到大岗山水电站工程中,解析智能反演获得坝区岩体的压缩蠕变参数。计算结果表明：解析-智能反演蠕变曲线与试验蠕变曲线的拟合程度比解析反演蠕变曲线与试验蠕变曲线的拟合程度好,说明解析-智能反演法获得的坝区岩体蠕变参数更为准确可靠,同时也验证了这种参数反演方法的有效性和合理性。该方法为高效快捷地反演坝区岩体的蠕变参数提供了重要理论指导。     

考虑围岩蠕变全过程与扩容的深埋隧洞非线性位移解

深埋隧洞围岩变形是一个复杂的非线性力学问题,其中岩石的蠕变全过程和扩容是两个重要的影响因素。引入扩容角考虑塑性体积变化的影响,推导Hoek-Brown屈服准则下考虑与不考虑洞周面力的深埋隧洞围岩非线性应力解。借助可描述蠕变全过程行为的河海模型,获得了围岩黏弹塑性区蠕变位移表达式。针对不同NVPB蠕变参数和不同材料参数m值情况,讨论分析了洞周面力与扩容角对隧洞洞壁蠕变位移的影响规律。结果表明：在高地应力作用下,采用非线性蠕变模型描述深埋隧洞围岩蠕变问题可获得蠕变全过程曲线;扩容角增大或洞周面力和材料参数m值减小时,相同时刻隧洞洞壁蠕变位移增大,对围岩长期稳定不利。研究结论对深埋隧洞围岩临崩预报具有一定指导意义。     

三轴压缩蠕变试验下石英云母片岩各向异性蠕变特性研究

对石英云母片岩进行三轴压缩蠕变试验,研究丹巴水电站石英云母片岩的三轴蠕变特性及其各向异性特性。按轴向荷载与层理面关系加工成平行组和垂直组2组试件,开展分级加载方式进行不同围压条件下的蠕变试验。试验研究表明,石英云母片岩具有蠕变特性,包括瞬时变形、衰减蠕变、稳定蠕变和加速蠕变阶段;采用带Kachanov蠕变损伤律的蠕变模型来描述石英云母片岩的蠕变特性,并进行蠕变参数辨识,拟合结果显示此模型能很好地描述石英云母片岩的蠕变特性;根据试验结果获得2组试件的长期屈服强度、破坏形态、瞬时变形参数和稳定蠕变速率,分析表明石英云母片岩的蠕变力学特性具有明显的各向异性特性。层理面与轴向荷载垂直的试件较层理面与轴向荷载平行的试件的强度、弹性剪切模量、体积模量和黏性系数相对较大,表现出较高的抗变形和抗破坏能力;平行组以剪切破坏为主,垂直组破坏时出现侧向鼓胀现象,显示出延性破坏的特点;2组石英云母片岩试件的瞬时应变量和稳定蠕变速率都随着应力水平的提高而增大。     

孔隙水压力分级加载砂岩蠕变特性研究

采用RLW－2000 M微机控制煤岩流变仪,以细粒砂岩为研究对象,对三轴压缩条件下岩石孔隙水压力分级加载蠕变试验进行了蠕变特性及模型研究,重点分析了孔隙水压力分级加载时蠕变条件下岩石的应变（应变速率）、等效孔隙体积（体积速率）演化曲线,同时对不同孔隙水压力分级加载条件下的岩石蠕变演化曲线进行了模型分析和对比。试验结果表明,逐级加载孔隙水压作用下细粒砂岩的蠕变曲线符合蠕变演化3阶段特征;分级加载水压力的孔隙体积演化规律符合微孔洞的损伤过程的3个阶段规律;利用西原体模型进行理论与试验蠕变曲线对比,蠕变方程曲线与试验曲线的演化规律吻合。