金龙山地区斜坡滑动优势面分析

据优势面分析原理和方法,对金龙山地区斜坡各种结构面所作的优势面分析结果显示:浅层强风化岩体中顺坡向剪切裂隙,是控制浅层顺层滑坡发生发展的滑动优势面;深层弱风化岩体中粘土岩风化软弱夹层、斜坡上段拉张裂隙与斜坡下段顺坡向剪切裂隙三者相组合,是控制深层顺层滑坡发生的滑动优势面。当地受滑动优势面控制的滑坡变形破坏模式有:浅层为蠕滑—拉裂,深层为滑移—弯曲。     

汶川地震后公路边坡崩塌灾害发育规律

震后崩塌是强烈地震造成的震裂山体在后期余震、降雨及重力作用下变形不断发展并再次发生的崩塌。基于对四川省省道S303线映秀-卧龙段震后公路边坡崩塌灾害的调查,通过空间分布、崩塌与物质组成、岩性、失稳斜坡坡度、坡高、坡形、坡向和崩塌形成机理的关系等方面的分析,得到了震后崩塌灾害的发育规律:1.震后崩塌分布规律与地震时引发的崩塌的规律一致,即地震时易发生崩塌的地段地震后仍然易发生崩塌。2.按照边坡物质组成,以岩质边坡崩塌占绝大多数,岩土组合体边坡次之;较坚硬岩石中发生的崩塌多而较弱岩石中发生崩塌少,沿线发生崩塌最多的是岩性为闪长岩、辉长岩和变质砂岩等坚硬岩石组成的斜坡。3.失稳斜坡坡度在36°～85°之间,主要分布在41°～60°之间,即震后崩塌灾害主要发生在40°以上的斜坡。映秀-耿达段和耿达-卧龙段发生崩塌的边坡坡度有明显的差别,映秀-耿达段集中在坡度为46°～60°的斜坡,而耿达-卧龙段集中在在坡度为41°～55°的斜坡。4.绝大多数崩塌发生在坡高150 m以内的斜坡上,映秀-耿达段和耿达-卧龙段发生崩塌的边坡高度有明显的差别,映秀-耿达段集中在高度为51～350 m的斜坡,而耿达-卧龙段集中在在高度<200 m的斜坡,尤以高度<100 m的最多。5.阳坡和阴坡的崩塌数量有明显的差异,阳坡发生崩塌的数量远远大于阴坡崩塌发生的数量。6.震后边坡崩塌的形成机理以滑移式崩塌和倾倒式为主。映秀-耿达段和耿达-卧龙段地处不同地质构造单元,由于岩性的差异,发生崩塌的斜坡的坡度、高度和主要形成机理具有差异性。     

顺层岩质边坡顺层滑动岩体范围分析

顺层滑移-拉裂是顺层岩质边坡中常见的一种破坏模式,顺层滑动岩体范围大小是该类边坡稳定性分析及其加固支挡结构设计的基础,是设计人员最关心的问题。考虑边坡开挖卸荷效应对边坡岩体力学参数的影响,建立了顺层岩质边坡顺层滑动岩体范围的计算式,利用重庆至怀化铁路沿线顺层岩质路堑边坡失稳破坏的调查资料进行对比分析,结果吻合较好。     

含水平软弱夹层斜坡变形破坏特征的振动台试验

已有研究结果表明,强度相对较低的软弱夹层会对地震波产生吸收或强化作用,在一定程度上控制了斜坡的地震动力响应及变形破坏特征。试验以振动台为研究手段,设计并完成含不同厚度水平软弱夹层的两个单面斜坡概念模型。通过记录斜坡模型的变形破坏过程,分析其动力响应特征。试验结果表明,斜坡模型的变形破坏与地震动力参数密切相关:1.模型在正弦波激振下较天然波变形明显;2.合成向ZX、水平单向X和竖直单向Z的激振下,变形程度依次减弱;3.随着激振强度增加,变形破坏愈明显。两模型的变形破坏均出现在坡体中上部,且最大破坏深度距坡顶约50 cm。含薄夹层斜坡的破坏范围分布于整个中上部,坡顶近1/2发生变形和滑移破坏,呈现出"拉裂-剪切-滑移-碎屑流化"破坏模式,而含厚夹层斜坡的破坏范围仅集中于软弱夹层以上坡肩以下,两侧未达坡体边缘的局部范围,形成浅表的"凹岩腔",呈现出"震裂-剥落"破坏模式。在相同的加载条件下,含薄夹层斜坡变形破坏先于含厚夹层斜坡。试验模拟再现了含水平软弱夹层斜坡在强震作用下的变形破坏规律,为地震诱发次生地质灾害的研究和防治提供了有力的依据。     

贵州水城曾家包包大型基岩滑坡的成因机制及稳定性

从滑坡的地质环境入手,通过地质调研及测绘,分析曾家包包大型基岩滑坡的特征、控制因素及成因机制,并运用sama法及不平衡推理法、毕肖普法对滑坡稳定性极限平衡进行计算分析。在此基础上,对在现今应力场作用下滑坡的稳定性采用了有限元模拟,并对模拟的结果进行分析,得出在天然条件下曾家包包滑坡曾处于稳定状态,岩体中的软弱夹层经长期持续的地下水浸润软化逐渐泥化形成倾角上陡下缓的贯通性滑移面,在雨季降雨异常集中期,岩体排水不畅形成较高的空隙水压力,斜坡岩体就会沿滑移面发生顺层滑移,从而形成大型基岩滑坡。     

金沙江某水电站左坝肩岩体双面倾倒形成机制

倾倒变形是层状边坡的一种主要变形破坏形式,在以往研究中,单面倾倒已研究较多而双面倾倒尚无研究成果。在充分研究金沙江某水电站左坝肩岩体双面倾倒变形特征基础上,对其形成机制进行了地质分析和数值模拟,揭示了双面倾倒岩体主要是在二次应力场作用下岩体沿片理面产生剪切错动、滑移、拉裂从而岩体产生弯曲或折断而形成的。其中顺倾边坡的倾倒变形始于坡脚,并以"滑移-倾倒"式逐渐向坡后发展,其倾倒扩展速率及倾倒深度明显小于反倾边坡;而反倾边坡初始倾倒位置不一定在坡脚,而是始于其最有利倾倒位置,该位置受初始坡形、所受应力及岩性组合等因素控制,并用数值模拟揭示了该水电站边坡初始倾倒位置在距坡脚约1/3坡高处,此后,当岩层倾角足够陡时,在该初始倾倒位置的上部岩层可表现出一定的"滑移-倾倒"性质,而该位置下部岩层则总是表现出"压致型"倾倒特征;无论顺倾还是反倾边坡,倾倒变形速率有从坡体中部附近向两端递减的趋势。     

沪蓉西高速公路贺家坪段顺层边坡结构稳定性分析

顺层边坡是工程实践中经常遇到也是较容易产生破坏的一类边坡,其失稳问题一直是工程界极为瞩目和急需解决的问题之一。从地质力学角度分析了顺层边坡的形成机制,抽象出了顺层边坡溃屈破坏的力学模型。利用结构力学的基本理论,推导出了相应的计算公式,并利用文中的理论方法,分析了沪蓉西高速公路贺家坪段顺层边坡(桩号k63-k64)的稳定性,结果与实际情况吻合较好。     

高县县城附近斜坡稳定性分析

四川省高县附近斜坡变形失稳灾害尤为严重。本文对斜坡变形失稳的类型,特点、形成原因、影响因素、破坏模式进行了分析,认为软弱岩层岩性。斜坡岩体结构、斜坡类型、岩体节理裂隙、地貌发育为决定斜坡稳定性的五主导因子。经深入研究,以定性定量标准把五因子分别划分为四级。利用斜坡变形模数计算五因子影响斜坡稳定性的权重等。从而获得了一种新的斜坡稳定性评价模式,把它运用于高县县城附近斜坡稳定性评价中,评价结果与实际基本相符。     

雅砻江上游深层倾倒体发育特征及形成演化机制

深层倾倒是雅砻江上游层状斜坡变形破坏的主要模式。利用基于演化过程的工程地质研究方法,分析深层倾倒体工程地质特性和内部变形破坏-力学机制,进行工程地质分区评价,并从变形过程和演化阶段上定性认识斜坡的整体稳定性。研究表明:区内深层倾倒体发育规模巨大、变形程度剧烈,且具有明显的分区性,为典型的互层倾倒;软硬相间的岩性组合、陡倾的岸坡结构,加之垂直层面密集节理的切割是深层倾倒体形成的控制性因素。在叠加有残余构造应力的自重应力场中,互层倾倒是受节理面和层面控制的复合倾倒模式,即:硬岩发生块状-弯曲倾倒,而软岩发生弯曲倾倒;受河谷演化控制,深层倾倒体主要经历4个演化阶段:卸荷回弹陡倾面拉裂阶段,初始变形阶段,板梁根部折断、剪切面贯通阶段以及破坏阶段,并最终转化为蠕滑-拉裂模式形成滑坡;变形破坏模式的转化是深层倾倒体进入累进性破坏阶段的重要标志,该滑动面受倾向坡外结构面控制,主要发生在强变形岩体中,而并非沿最大弯折带发育。     

厚层堆积层震裂斜坡变形特征及破坏机制——以小金县某震裂不稳定斜坡为例

“5.12”汶川特大地震形成了震区大量的震裂不稳定斜坡,其中绝大部分发生在厚层堆积层斜坡中,这类次生地质灾害有着特殊的力学破坏机制.以小金县某不稳定斜坡为例,研究了高程、地形坡度、岩土体结构条件等对斜坡动力响应的影响,初步分析了厚层堆积层震裂斜坡的变形特征及破坏机制.认为,在地震动力作用下厚层堆积物斜坡往往出现潜在多级滑动面的现象,且破裂面多沿着堆积层中某些曲面发生滑动破坏,这与地震瞬间拉张破坏在斜坡体中产生的震裂缝深度和延伸有关.总的来说,震裂不稳定斜坡的失稳可以认为是地震使边坡岩土体力学参数降低、震后地下水的软化共同作用下累计破坏的结果.     

灌溉诱发突发性黄土滑坡机理研究

系统揭示黑方台突发性黄土滑坡物理力学机理,对滑坡防治具有重要的作用。自上世纪六十年代年黑方台常年的农业灌溉诱发了大量20~40 m厚的饱和突发性黄土滑坡。本研究在野外调查的基础上,通过分析滑坡的变形破坏特征,针对分布范围广、危害性较大的突发性黄土滑坡,利用室内GDS三轴试验和模型试验,分析研究了饱和黄土的应力应变特性及突发性黄土滑坡的力学机制。三轴试验结果表明,当围压小于300 kPa时,饱和黄土可产生完全液化,并处于流塑状态;当围压大于300 kPa时,饱和黄土仅产生部分液化,仍具有一定的抗剪强度。饱和黄土的应力—应变模式均表现为强烈的应变软化—剪缩型,并具有一定的稳态特性。模型试验表明突发性黄土滑坡的变形破坏过程可大致分为底部浸水饱和—毛细水上升—持续蠕动变形—突发性破坏4个阶段。斜坡发生突发性破坏时,孔隙水压力激增,但总应力仍大于孔隙水压力,黄土滑坡发生部分液化,饱和黄土仍具有一定的强度,为突发性黄土滑坡发生提供了应力和能量积累的力学条件。研究从有效应力原理的角度阐述了突发性黄土滑坡的力学机理,可以为滑坡的防治治理提供一定的理论依据。     

滑坡综合预报方法研究

滑坡综合预报是基于对滑坡发育状态的形成条件类比分析和滑坡位移历时分析的综合方法,从滑坡形成条件、变形状态、诱发因素的方式和影响程度的动态分析入手,结合滑坡加速变形破坏阶段的位移历时特征,建立滑坡预报模型,实现对滑坡的预报.与其他滑坡预报方法相比,滑坡综合预报方法的综合性强,能较好的确定滑坡的发育状态,分析滑坡发生剧烈滑动的可能性,能对不同发育阶段的滑坡做出准确判别.     

The effect of confining boundary on soil deformation in one dimensional frost heave tests and the theoretical volume correction

Frost heave is one of the major complications in highway construction in cold regions. Laboratory experiments are im-portant in the study frost heave behavior of soils, and one-dimensional frost heave ...     

古尔班通古特沙漠南缘风沙土土壤水分特征与毛管水最大上升高度

为确定古尔班通古特沙漠南缘地下水深埋区毛管上升水的最大上升高度,对划分固沙植物水分来源提供理论依据,于2016年3月~2018年11月,采用中子仪法对试验地0~10 m土层土壤含水量进行观测,分析沙丘不同坡位土壤含水量的季节变化情况,并利用最大分子持水量与土壤含水量曲线交会法确定试验地毛管水的最大上升高度。结果表明：沙丘不同坡位0~130 cm土层的土壤含水量受外界气象因素影响较大,随季节变化规律明显;130 cm土层以下至570~760 cm土层为土壤含水量较为稳定的干沙层;而570~760 cm以下土层的土壤含水量主要受地下水水位波动和毛管上升水的影响,其含水量变化上界可看作是毛管水的最大上升高度。试验地的最大分子持水量为0.026 1 cm³·cm^-3,且沙丘不同坡位毛管水的最大上升高度分布在250~290 cm之间。     

The shapes of cold, high mountains in sedimentary rocks

Terzaghi (Geotechnique 12 (1962) 251) and Young (Young, A., 1972. Slopes. Oliver and Boyd, Edinburgh, 288 pp.) described the stable forms of slopes in sedimentary rock masses, assuming penetrative discontinuities, which are parallel to bedding and joints which are perpendicular to bedding. The only movements considered were slides along bedding. Experience in the Canadian Rockies indicates that the cohesionless rock masses that exist at or above tree line may also move by toppling, buckling and sliding along joints. These processes also act to limit the inclinations of stable slopes. Rock strength is a factor in the critical height of a slope that buckles. The processes can be represented as fields on a process diagram, a plot of slope inclination against bedding dip, using the basic friction angles of the rocks present.The process diagram also separates five common mountain peak shapes, which form on homoclinal sequences of beds. Castellate and Matterhorn mountains occur in sub-horizontal beds, cuestas develop in gently to moderately dipping beds. Hogbacks formed in moderately to steeply dipping beds have similar slope angles on both cataclinal and anaclinal slopes. Dogtooth mountains occur in steeply dipping sub-vertical beds.     

Stress relaxation of warm frozen soil under drained or undrained conditions

To investigate the influence of drainage conditions on stress relaxation characteristics of warm frozen soil, a series of laboratory tests were carried out under drained and undrained conditions. The results indicate that confining pressure obviously influences the relaxation process of warm frozen soil. Under undrained condition, with increase in confining pressure, the critical relaxation duration tends to grow as well as instantaneous relaxation. But the relaxation rate is sensitive to confining pressure in the initial stage, and with further development, the effect tends to diminish. Under drained condition, the relaxation rate is greater than that under undrained condition in the initial stage but with the development of relaxation, the difference decreases. The volumetric deformation of warm frozen clay under drained condition is much larger than that under undrained condition.     

Effects of environmental change on scree slope development throughout the postglacial period in the Chic-Choc Mountains in the northern Gaspé Peninsula, Québec

The combined study of present-day processes and stratigraphic data, has permitted the reconstruction of the dynamics of scree slopes of the northern Gaspé Peninsula throughout the postglacial period. In this region, liberated progressively from beneath an ice cover between 13,500 and 10,000 years BP, the scree slopes have to be seen as an integral part of a regional geosystem. Evolution of these slopes has been rapid, influenced by local paraglacial conditions (glacio-isostatic rebound, glacio-eustatic fluctuations, and re-equilibration of glacially over-steepened rockwalls) which operated against a backdrop of Late Glacial and Holocene climatic fluctuations. During the Younger Dryas and part of the Early Holocene period, as the foot slopes emerged from beneath the Goldthwait Sea, the basal part of several scree slopes advanced onto marine terraces as lobate rock glaciers, under the influence of a periglacial climate, characterised by permafrost. Many scree slopes continued to transfer debris downslope after regional establishment of a closed forest cover at ca. 7250 years BP. Forest colonisation in the early pre-emergent phase of the postglacial period was retarded, due to constant replenishment of the debris removed from the foot slopes by marine processes. In the later post-emergent phase, development of a complete forest cover has only been possible on slopes where the summit rockwall segment has been completely eliminated, a condition not yet fulfilled for many geomorphologically active scree slopes of the region. In fact, both of these paraglacial influences have been diachronous on a regional scale. Advance upslope of the forest front on the scree slopes appears to have been slow, difficult and subject to periodic regressions of possible climatic origin, as indicated by numerous buried soils in colluvial stratigraphic sequences, and for the past 150 years by dendro-ecological studies. Stratigraphic exposures, along with direct observation of slope events, have revealed the operation of a large variety of debris transfer processes, including niveo-aeolian sedimentation and frost-coated clast flows, the latter representing an important process first recognised on the scree slopes of Gaspésie.     

Hypsometric Analysis of Headwater Rock Basins in the Dolomites (Eastern Alps) Using High‐Resolution Topography

Hypsometric curves and integrals are effective tools for rapid quantitative assessments of topography. High‐resolution digital terrain models derived from airborne LiDAR data have been analysed to study the hypsometry of small headwater rock basins (drainage areas up to 0.13 km²) in three study areas in the Dolomites (Eastern Alps) that have similar lithologies and climatic conditions. Hypsometric curves in the studied rocky headwaters display a variety of shapes and present remarkable differences between neighbouring basins. Hypsometric integrals show generally high values in the three study areas (>0.42, mean values between 0.51 and 0.65). The extent of the scree slopes located at the foot of rock basins in the three study areas is larger in the area with lower hypsometric integrals and indicates consistency between the development of basin erosion, which is shown by the hypsometric integral, and debris yield, represented by the extent of scree slope. No clear relations were observed between the hypsometric integrals and basin area and shape. When extending the analysis to larger basins, which encompass rocky headwaters and downslope soil‐mantled slopes, a negative correlation is found between the hypsometric integral and catchment area, suggesting that the scale independency of the hypsometric integral occurs essentially in headwater rock basins. Geomorphometric indices (residual relief and surface roughness) have contributed to interpreting the variability of surface morphology, which is related to the geo‐structural complexity of the catchments.     

古尔班通古特沙漠沙丘主要灌木的种群数量动态

种群数量动态的研究是认识种群的生存现状及发展动态的前提。通过对古尔班通古特沙漠固定沙丘、半固定沙丘和流动沙丘上主要固沙灌木的样地调查,分析了固沙灌木的年龄结构,建立了3种沙丘上固沙灌木的静态生命表和存活曲线。结果表明：（1）固沙灌木的存活个体数呈逐级递减的趋势,幼龄个体占有很高的比例;固定沙丘上梭梭（Haloxylon ammodendron）呈现Ⅰ型存活曲线,种群退化,白梭梭（Haloxylon persicum）呈现Ⅱ型存活曲线,种群稳定;（2）半固定沙丘上白梭梭呈Ⅱ型存活曲线,种群相对稳定;沙拐枣（Calligonum mongolicum）和油蒿（Artemisia ordosica）均呈现Ⅰ型存活曲线,种群处于退化状态;（3）流动沙丘上沙拐枣呈现Ⅲ型存活曲线,种群有较大的增长潜力,白梭梭呈现出Ⅱ型存活曲线,种群相对稳定,油蒿呈现出Ⅰ型存活曲线,种群处于不稳定的退化状态。