岩质边坡锚固参数正交优化分析及应用

岩质边坡防护的最有效措施就是锚固工程。然而锚固参数(包括锚杆或锚索长度、锚固间距、预应力大小等)的选取至今在理论上未能很好解决,在实际工程中也未体现出合理的优化设计。以云沱段狮子包边坡2-2′剖面(K0 85.7 m)为例,运用正交试验设计法分析锚固参数的组合方案,以边坡稳定性系数作为评价指标,分别改变锚固参数,以此分析对边坡稳定性的影响。研究结果表明,对边坡稳定性影响显著的因素由大至小的顺序是:预应力大小、锚固间距、锚杆长度。以此研究结果为该实例的锚固支护参数选取确定了设计方案,最后采用有限差分程序FLAC3D进行了锚固效果数值分析验证。     

三处滑坡工后锚索承载性能现场试验对比分析

工后边(滑)坡预应力锚固工程的长期工作性能是影响锚固工程安全性的一个关键问题。通过一种改进的拉拔检测设备,对重庆三处滑坡工后锚索结构进行了锚索抗拔力检测。通过对各工点检测结果的分析,对各工点锚索结构物当前预应力状态,预应力损失率,锚索安全储备进行了科学判定,为补强整治提供依据。对比分析了造成三处滑坡预应力损失差别较大的原因,岩体蠕变变形及锚索的松弛耦合变形是导致工后锚索预应力损失的主要原因,对于过于松散破碎或含水量较大的滑坡体尽量避免采用预应力锚索结构。通过对比分析各工点工后锚固工程的应力状态及锚索破坏方式表明,锚固段破坏是引起锚固工程失效的主要方式之一,今后锚索工程施工时,应重点注意锚索的长度及注浆等施工质量。对于大型的边(滑)坡中的预应力锚固工程建议安装锚索测力设备,以便时掌握预应力损失情况,及时进行补张拉,防患于未然;对于未安装锚索测力设备的,建议封锚时,预留钢绞线长度大于5 cm,以便工后进行拉拔检测试验。此种改进的拉拔检测设备具有简单、实用、易操作等特点,值得在工后岩土锚固工程长期性能评价领域推广应用。     

拉力分散型锚索在边坡二次加固中的应用

一些边坡治理后由于工程加载、雨水入渗以及地震等影响,局部会出现新的变形破坏,需要根据边坡和治理工程结构的变形情况进行二次加固(补强加固).以拉力分散型锚索为例,首先分析其结构特征及优越性.考虑松散地层的软化特性,借助剪滞理论分析模型给出拉力分散型锚索锚固段上灌浆体与锚固岩层界面剪应力的计算公式,在此基础上,对一公路边坡二次加固中采用的拉力分散锚索锚固段荷载分布进行了分析和讨论.实例分析和监测结果表明,拉力分散型锚索锚固段荷载分布更为合理,有助于维护锚固体系的预应力水平.拉力分散型锚索用于边坡二次加固具有广泛的应用前景.     

磨刀溪岩石滑坡分析与治理

磨刀溪岩石滑坡由于人工开挖、在支挡不当的情况下产生并逐步扩大。对此,着重采用了工程地质力学法对该滑坡进行了分析,明确了该滑坡为一切层滑坡,其发生发展与岩层的结构面关系密切。在此基础上以推力传递系数法及地基系数等为理论,确定以一排抗滑桩及一排锚索抗滑桩进行支挡,并在下排桩前采用锚索框架对桩前岩土体进行加固,以确保抗滑桩的锚固段不松弛变形,同时结合疏排水的措施对该滑坡予以彻底治理,从实践看最后一次的治理取得了成功。同时分析了前面几次失败的治理经历,从中总结了很多有益的经验和教训,并从治理实践中证明了该滑坡治理措施的合理性和有效性,值得同类工程借鉴。     

应用于滑坡的拉力型锚索失效机理

拉力型锚索常用于公路边坡支护工程中,在进行锚固体的结构设计时,注浆体与岩石粘结界面的强度往往被高度关注.在广泛调研西南山区失稳破坏的公路边坡时发现,拉力型锚索最为薄弱的部位并非注浆体与岩石粘结界面.因此,设计11种不同配合比的注浆体,将80根拉力型锚索锚固在软岩及硬岩中,采用拉拔试验对锚索的破坏模式进行研究.结果表明:拉力型锚索常见的破坏模式是钢绞线与注浆体之间的脱粘破坏.选择合理的力学计算模型,获得内锚固段两个粘结界面的应力分布弹性解,分析表明:钢绞线与注浆体粘结界面的峰值应力位于锚孔孔口处,应力分布不均匀程度高,致使孔口处的钢绞线注浆体粘结界面首先发生脱粘破坏,脱粘界面以渐进的方式向内锚固段末端传递,最终导致钢绞线从注浆体中旋转拔出.建议上述研究成果在以后的规范修订和锚固工程设计时引起足够的重视.最后,给出了一个钢绞线与注浆体脱粘破坏的工程实例.     

滑坡危险度评价的地形判别法

选取影响滑坡发育的坡度、坡形、坡向、坡体的相对高度和地形与地层产状的组合关系5个主要地形因素，结合三峡库区重点滑坡段(云阳-巫山)205个滑坡统计资料，利用地形判别法，对典型滑坡危险度进行评价。将各地形判别因子在区域滑坡发育上的贡献率作为评价典型滑坡危险度的评价值，利用层次分析法，建立典型滑坡危险度判别矩阵。将判别矩阵的归一化特征向量作为判别因子的权重，得到典型滑坡的危险度。通过建立典型滑坡危险度评价表，对滑坡进行有效的管理。此研究方法有效地避免了对评价因子赋值的主观性，并提出了对不同危险度等级的滑坡管理措施。     

河北省滦平县第一中学新校区南侧山体滑坡的治理方案研究

针对滦平县第一中学新校区建设工程南侧的滑坡灾害对学校产生的安全威胁,本文对滑坡灾害特征和诱发因素进行了研究,进而提出了治理措施.结果表明:滑坡变形特征较为明显,前部滑坡区的崩滑、张拉裂缝发育,后部变形区的张拉裂缝发育处于基本稳定状态;根据滑坡的危害对象,对滑坡的治理采用"预应力锚索抗滑桩+格构梁坡脚支挡、锚杆加固岩层坡...     

加固含水平软弱层高陡边坡预应力锚索倾角的取值范围

用直线和曲线滑面两种模型，模拟预应力锚索加固含有水平软弱层的高陡边坡的潜在滑动面，通过对锚索加固的力学机理分析来阐述预应力在滑动面主滑方向上产生分力的原因。从锚索受力角度上对锚索倾角的取值范围进行探讨，结合实际造孔过程有不同程度的孔斜或弯曲以及获取较好的锚固灌浆效果，就仰角锚固和俯角锚固两种锚固条件分别得出锚索倾角的取值范围，并以此来判定锚索的预应力是否会在滑动面走向方向上产生不利于坡体稳定的下滑力。     

山丘区工程滑坡分类与灾害防治

通过对山丘区由于基本建设过程中人为处置不当引发的工程滑坡实例的分析,按滑坡成因将工程滑坡分为：场地选址不当、切脚开挖且放坡过陡、斜坡加载填土不当和环山渠渗漏降低土体抗滑力等5类。在此基础上提出了工程滑坡灾害的防治对策和治理措施,并建议在山丘区工程滑坡治理中,优先选用预应力锚固桩。     

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 landslide response of alpine basins to post-Little Ice Age glacial thinning and retreat in southwestern British Columbia

The role of post-Little Ice Age (LIA) Neoglacial retreat on landslide activity is investigated in 19 alpine basins along the upper Lillooet River Valley, British Columbia. We examine how Neoglacial scouring and glacial recession have modified hillslope form and slope stability, and construct a decision-making flowchart to identify landslide hazards associated with glacial retreat. This work is based on field mapping, GIS analysis, statistical associations between landslides and terrain attributes, and a comparison between Neoglaciated and non-Neoglaciated terrain within each basin.The bedrock landslide response to glacial retreat varies appreciably according to lithology and the extent of glacial scour below the LIA trimline. Valleys carved in weak Quaternary volcanics show significant erosional oversteepening and contain deep-seated slope movement features, active rock fall, rock slides, and rock avalanches near glacial trimlines. Basins in stronger granitic rock rarely show increased bedrock instability resulting from post-LIA retreat, except for shallow-seated rock slides along some trimlines and failures on previously unstable slopes. In surficial materials, landslides associated with post-LIA retreat originate in till or colluvium, as debris slides or debris avalanches, and are concentrated along lateral moraines or glacial trimlines.Significant spatial association was also observed between recent catastrophic failures, gravitational slope deformation, and slopes that were oversteepened then debuttressed by glacial erosion. Eight out of nine catastrophic rock slope failures occurred just above glacial trimlines and all occurred in areas with a previous history of deep-seated gravitational slope movement, implying that this type of deformation is a precursor to catastrophic detachment.     

乔木的斜向支撑效能及其坡面稳定意义

以滇中地区的松林为例,初步定量探讨了乔木对顺坡有的浅层土壤的斜向支撑作用。研究,树根可能提供的锚固力可达０．６９ｋＮ;在有效的锚固作用下,单株树干的支撑力（抗滑力）最高为０．４２ｋＮ,平均为０．１７ｋＮ;受斜向支撑作用的影响,本来不稳定的浅层松散物质的稳定性系数Ｆ值,由０．５４提高到１．１０,使坡面成为稳定斜坡。如果在特定条件下,树根的锚固力全部转化为支撑力,坡面的Ｆ值可以达到２．８２。     

Late glacial and Holocene marine records from the Independence Fjord and Wandel Sea regions, North Greenland

The first marine sediment cores from the unexplored Independence Fjord system and the Wandel Sea, North Greenland, have been investigated to reveal the glacial marine history of the region. Two key sites in the Independence Fjord system, and an earlier analysed site from the Wandel Sea continental slope, off the mouth of Independence Fjord, are presented. The Independence Fjord sites reveal an early Holocene record (10.0–8.9 Kya) of fine-grained reddish muds with calcareous microfossils, dominated by the benthic foraminifera Cassidulina neoteretis . We suggest that a semi-permanent fast ice cover characterized the region in the early Holocene, and that the deeper troughs in the mouth region of the Independence Fjord system were intruded by subsurface Atlantic water. A stiff diamicton, at least 1.3 m thick, with coal and sandstone clasts of mainly local origin, and a 0.5-m-thick Holocene cover, are found in one of the sites. The diamicton is assumed to represent a subglacial till predating the early Holocene sediments (>10 Kya). Shallow seismic records off the mouth of Independence Fjord reveal kilometre-sized troughs with signs of glacial erosion, till deposition and a Holocene glaciomarine deposition. These features could indicate that glacial ice debouching from the Independence Fjord system at some time during the last glacial period extended to the mid-outer Wandel Sea shelf. Data from a high-resolution sediment core previously retrieved from the adjacent Wandel Sea slope indicate that the maximum ice sheet advance in this area culminated about 25–20 Kya.     

摆浪河流域的ESR年代学与祁连山第四纪冰期新认识

摆浪河发源于走廊南山北坡,是黑河的一条支流。在河源区保存有六条完整的冰碛和较为完整的阶地序列。应用ESR技术对采自该处较老的第三、第五、第六套冰碛和冰水成因的主阶地上的砾石层与上覆黄土进行了测年研究,测试结果分别为13.4ka、135.3ka、462.9ka、130.1ka、130.2ka。根据测试的结果并结合地貌地层学得出：3800m以上“U”型谷中的第一、第二套冰碛为全新世中小冰期、新冰期沉积的冰碛;第三套冰碛物是末次冰期晚期沉积的,与深海氧同位素2阶段相对应;第五套冰碛物是与深海氧同位素6阶段相对应的冰期沉积的;第六套冰碛物是与深海氧同位素12阶段相对应冰期沉积的;由此推断介于第三套与第五套冰碛之间的第四套冰碛是末次冰期早期沉积的,即可与深海氧同位素4阶段相对应。主阶地与第五套冰碛是同一时期形成的,这也与地貌地层学的推断相一致,从此处完整的冰川沉积序列还可以得出：在更新世中,祁连山地区至少存在三次冰期,经历四次冰川作用。祁连山部分地段或是整体至少在463ka前就已经抬升到当时冰期气候相耦合的高度。ESR可以用于河流、冰川沉积物的测年。     

Supraglacial Debris Supply in the Cuerpo de Hombre paleoglacier (Spanish Central System): Reconstruction and Interpretation of a Rock Avalanche Event

During the deglaciation stages of the last glacial period a rock avalanche took place on the glacier that occupied the upper sector of the Cuerpo de Hombre Valley (Sierra de Béjar). The material displaced during the avalanche fell onto the ice, was transported by the glacier and later deposited as supraglacial ablation till. The cause of the avalanche was the decompression of the valley slopes after they were freed from the glacier ice (stress relaxation). Reconstruction of the ice masses has been carried out to quantify the stress relaxation that produced the collapse. The rock avalanche took place on a lithologically homogeneous slope with a dense fracture network. The avalanche left a 0.4 ha scar on the slope with a volume of displaced material of 623 ± 15 × 10³ m³. The deposit is an accumulation of large, angular, heterometric boulders (1–100 m³ in volume) with a coarse pebble‐size matrix. The avalanche can be explained as a relaxation process. This implies rock decompression once the glacier retreat left the wall ice free (debuttressing). Calculations show that the avalanche took place where the decompression stresses were highest (130–170 kPa). In the Spanish Central System paleoglaciers the largest accumulation of morainic deposits occurred after the glacial maximum and the earliest stages of the ice retreat. The process described here is used as an example to formulate a hypothesis that the largest accumulations of tills were formed in relation to enhanced slope dynamics once some glacier retreat had occurred.     

Tree-ring evidence linking late twentieth century changes in precipitation to slope instability,central New York state,USA

The Burtonsville landslide in central New York, USA, is a kilometer-scale rotational block failure in glacial till that was likely initiated by incision of the adjacent Schoharie Creek. Although the timing of initial failure is unknown, relatively fresh scarps and tilted surfaces suggest that movement is post-glacial and active. The river currently erodes the toe slope and it removed significant material during flooding associated with Hurricane Irene (August 2011). We retrieved tree cores from 111 trees across the landslide to reconstruct modern movement and block tilting as it related to moisture conditions in the region. Our data show that trees across the slide are in sync with respect to the stress response indicated by reaction wood. The magnitude of response to slope instability, as inferred from eccentric growth, has varied considerably across the site. We hypothesize that macropore development during the driest periods, and the differential rate at which water has reached subsurface failure planes, has caused the observed slope instability. The combination of a wetter precipitation regime and slope instability leads to higher sediment loads in the adjacent stream and serves as a useful analogy for similar watersheds in the region.     

Trends in Year-To-Year Fluctuations in Surface Air Temperature,Canadian Arctic

The northwest portion of the Tekonsha Moraine has traditionally been considered to be a product of, and composed of sediments from, the Lake Michigan Lobe. A recent study has also correlated till from the moraine with an exposure (Ganges till) along the shore of Lake Michigan. The results of this paper contradict those interpretations. Multiple lines of evidence—till fabrics, 7-Å/10-Å peak height ratios of clay minerals, indicator stones, morphology, and elevation relationships—indicate a Saginaw Lobe origin for the till and glaciofluvial sediments. Moreover, aerial photographs reveal the presence of ice-stagnation topography. The moraine is herein reinterpreted as a hummocky and pitted (collapsed) outwash plain/kame moraine. Given that this feature has long been considered a moraine, similar landforms in Michigan and elsewhere may be more common than heretofore recognized. [Key words: glacial geomorphology, Michigan, Quaternary, Tekonsha Moraine.]     

地震作用下顺层岩质边坡稳定性的拟静力分析

通过对顺层岩质边坡的受力分析,应用极限平衡理论和Mohr-Column准则,按照Bishop关于边坡稳定性安全系数的定义,推导出在爆破震动载荷作用下,用于判别顺层岩质边坡稳定性的计算方法。研究结果表明垂直向下、水平指向坡外的爆破荷载以及两者的联合爆破荷载对边坡稳定性影响最大,尤其是后两者;水平指向坡外、垂直向下爆破荷载拟静力系数分别与边坡稳定性安全系数间呈负指数关系和S曲线关系;从动荷载拟静力系数0起,爆破震动水平指向坡外、垂直向下动荷载拟静力系数每增加0.05,有层裂长度的顺层边坡安全系数分别减少7.79%-10.67%、1.28%-1.98%,无层裂的顺层边坡安全系数分别减少7.61%-10.55%、1.47%-2.29%。同时,爆破震动产生的层裂长度、边坡长度以及联合爆破荷载的方向对顺层边坡稳定性也有影响。