断层破碎带条件下组合式圆截面抗滑桩加固边坡效果研究

随着我国公路建设不断向山区深入, 在地质构造复杂区公路边坡遇到断层破碎带的情况日渐增多, 亟需开展阻滑能力强的抗滑桩结构加固边坡研究。传统的人工挖孔桩施工模式存在高风险、低效率等缺点, 而组合式圆截面抗滑桩具有施工效率高、安全便捷等特点, 为此, 探究其对含断层破碎带边坡的加固效果具有现实意义。采用自主设计的边坡物理试验系统, 设计了5种不同破碎带厚度与组合式圆截面抗滑桩组合的物理模型, 采用坡顶逐级加载的方式模拟加载, 监测桩身应变、桩顶位移和桩后土压力, 采用高速相机捕捉滑体变形破坏图像, 并使用粒子图像测速(PIV)技术对图像进行处理。研究结果表明: 组合式圆截面抗滑桩通过限制桩后滑体水平位移, 并将滑体限制在前、后排桩间来达到加固边坡的效果; 滑体演化分为变形压密、加速变形和破坏滑移3个阶段; 前、后排桩桩后土压力比值介于1/3~1/2之间; 随断层破碎带厚度增加, 滑体水平滑移速率增大, 组合式圆截面抗滑桩的桩顶位移增大, 桩身最大正弯矩减小。模型试验与数值模拟计算的弯矩及桩顶位移较为吻合, 研究成果可为边坡工程组合式圆截面抗滑桩设计提供一定借鉴与参考。      

锚索抗滑桩系统内力变形研究

在对锚索抗滑桩系统内锚索与抗滑桩受力状态综合分析的基础上,认为锚索的拉伸变形对锚索抗滑桩系统的内力及变形存在一定影响,基于锚索与抗滑桩的变形协调原理,提出了锚索拉力及其变形的计算方法,推导了抗滑桩桩身位移和内力的计算公式,并将该方法用于工程实例分析。通过与其他方法比较,说明使用该方法计算锚索抗滑桩的合理性和经济价值,并分析了锚索变形以及拉力大小对锚索抗滑桩系统内力变形的影响,所得结果已得到后期模型试验的数据支持。     

Dynamic response of a slope reinforced by double-row antisliding piles and pre-stressed anchor cables

Large-scale shaking table tests were conducted to study the dynamic response of a slope reinforced by double-row anti-sliding piles and prestressed anchor cables. The test results show that the reinforcement suppressed the acceleration amplification effectively. The axial force time histories are decomposed into a baseline part and a vibration part in this study. The baseline part of axial force well revealed the seismic slope stability, the peak vibration values of axial force of the anchor cables changed significantly in different area of the slope under seismic excitations. The peak lateral earth pressure acting on the back of the anti-sliding pile located at the slope toe was much larger than that acting on the back of the anti-sliding pile located at the slope waist. The test results indicate an obvious load sharing ratio difference between these two anti-slide piles, the load sharing ratio between the two anti-sliding piles located at the slope toe and the slope waist varied mainly in a range of 2-5. The anti-slide pile at the slope waist suppressed the horizontal displacement of the slope surface.     

Effect of the inclined weak interlayers on the rainfall response of a bedded rock slope

Engineering experience shows that outward dipping bedded rock slopes, especially including weak interlayers, are prone to slide under rainfall conditions. To investigate the effect of inclined weak interlayers at various levels of depth below the surface on the variation of displacements and stresses in bedded rock slopes, four geo-mechanical model tests with artificial rainfall have been conducted. Displacements, water content as well as earth pressure in the model were monitored by means of various FBG (Fiber Bragg Grating) sensors. The results showed that the amount of displacement of a slope with a weak interlayer is 2.8 to 6.2 times larger than that of a slope without a weak interlayer during one rainfall event. Furthermore, the position of the weak interlayer in terms of depth below the surface has a significant effect on the zone of deformation in the model. In the slope with a high position weak interlayer, the recorded deformation was larger in the superficial layer of the model and smaller in the frontal portion than in the slope with a low position weak interlayer. The slope with two weak interlayers has the largest deformation at all locations of all test slopes. The slope without a weak interlayer was only saturated in its superficial layer, while the displacement decreased with depth. That was different from all slopes with a weak interlayer in which the largest displacement shifted from the superficial layer to the weak interlayer when rainfall persisted. Plastic deformation of the weak interlayer promoted the formation of cracks which caused more water to flow into the slope, thus causing larger deformation in the slope with weak interlayers. In addition, the slide thrust pressure showed a vibration phenomenon 0.5 to 1 hour ahead of an abrupt increase of the deformation, which was interpreted as a predictor for rainfall-induced failure of bedded rock slopes.     

基于物理模型试验的杆塔基础滑坡防护措施效果研究

大量穿越山地丘陵区的高压输电线路杆塔基础常位于滑坡灾害高易发斜坡地段, 施加适当防护措施提高其稳定性, 是保障输电线路持续安全运行的关键。为研究不同防护措施对杆塔基础滑坡的防护效果, 以湖北省巴东县燕子滑坡为地质原型, 设计制作物理试验模型, 分别开展了极端降雨条件下滑坡在无防护、施加抗滑桩与格构护坡时的物理模型试验, 从试验角度揭示了滑坡变形破坏特征与不同防护措施的防护效果。试验结果表明: 在2种极端降雨工况(50, 100 mm/h)下, 无防护的滑坡体历经了坡表冲刷、裂缝扩展、局部垮塌变形与整体滑动的演化过程; 抗滑桩措施对滑坡整体的防护效果显著, 滑坡整体处于稳定状态, 杆塔基础变形较小, 杆塔倾斜率满足规范, 但坡表会出现冲刷垮塌现象; 格构护坡措施能有效减少坡面冲刷和坡脚垮塌风险, 但在持续强降雨条件下对杆塔基础的整体稳固作用稍弱。物理模型试验结果与滑坡历史变形和实际治理效果吻合, 试验结论可为类似杆塔基础滑坡的破坏机理研究与防护工程设计提供借鉴。      

基于“三段法”的锚拉桩桩身内力计算方法与应用

针对抗滑桩常因地质条件、地形地貌等原因导致受荷段底面与嵌固段顶面不在同一水平面的情况,将此段划为次受荷段,并推导了次受荷段桩后设计荷载大小计算公式和荷载分布公式,以及在弹性地基梁和悬臂梁模型下的适用于悬臂桩和锚索桩内力与挠度计算通用公式。以巴东县焦家湾移民安置点库岸防护工程预应力锚索桩为例,研究次受荷段对抗滑桩内力和挠度影响。结果表明:忽略次受荷段后土压力作用的传统计算方法会使桩身弯矩计算结果偏小,导致桩身配筋量不足,存在设计安全隐患。再以锚索排数、位置为控制变量,研究其对预应力锚索桩内力和挠度的影响,提出预应力锚索可有效地降低抗滑桩工程造价;增加预应力锚索的排数有利于调节抗滑桩内力分布,设计时应优先考虑将锚索设置为多排锚索。      

不同布锚方式对锚索抗滑桩受力与变形影响的物理模型试验研究

锚索抗滑桩是滑坡的主要支护结构之一。目前, 软硬相间地层条件下锚索抗滑桩的受力与变形特征尚缺乏系统研究。以软硬相间地层为地质背景, 基于自主研发的柔性测斜仪和自动加载系统, 构建了锚索抗滑桩加固滑坡物理模型试验系统, 开展了锚索抗滑桩加固滑坡的物理模型试验, 揭示了推力不断增加过程中抗滑桩、锚索和滑体的变形与受力特征, 对比研究了布锚方式对桩-锚受力与变形的影响规律, 通过数值模拟的方法分析了软硬相间地层对锚索抗滑桩的影响机理, 并以双锚点抗滑桩为例进行了理论分析。研究结果表明: ①在滑坡-锚索抗滑桩体系中, 桩身各点位移和滑体深部位移均随桩身深度的增加而减小, 滑体后部位移速率大于中部, 且滑体位移速率大于桩身位移速率; ②单锚点抗滑桩的桩-锚推力分担比经历了4个阶段的变化, 趋于稳定时桩-锚推力分担比约为9∶1, 锚索拉力作用下桩身弯矩呈"S"型分布, 正负弯矩非对称; ③锚固角度越大, 锚索拉力的增速越大, 不同锚固角度对桩身内力值的影响主要体现在受荷段; ④多锚点抗滑桩结构的锚索分担更多的推力, 与单锚点抗滑桩相比, 双锚点与三锚点抗滑桩的最大桩身弯矩分别减小了22.41%和40.55%;⑤与均质地层相比, 软硬相间地层中软、硬岩交界面处基岩应力发生突变, 不同软岩厚度比和桩底是否嵌入硬岩, 均对锚索拉力和桩-岩之间的相互作用有不同程度的影响; 其次, 双锚点抗滑桩内力的理论值与试验结果较为接近。本研究成果可为软硬相间地层中锚索抗滑桩加固滑坡工程的优化设计提供依据。      

Model test of the stability degradation of a prestressed anchored rock slope system in a corrosive environment

The long-term stability of a prestressed anchored slope might be influenced by the durability of the anchorage structure. To understand long-term stability of anchored rock slopes, the research presented herein evaluated the performance evolution of a prestressed anchored bedding slope system in a corrosive environment by model test. The corrosion process in a prestressed anchor bar was monitored in terms of its open-circuit potential(OCP), corrosion current density(CCD), and electrochemical impedance spectroscopy(EIS). The stability of the prestressed anchored slope was evaluated by monitoring changes in anchorage force and displacements. The experimental results show that prestress and oxygen could reduce the corrosion resistance of the anchor bar, and anchor bars in a chloride-rich environment are very susceptible to corrosion. Prestressed tendons in a corrosive environment suffer a loss of anchorage force, the prestress decreases rapidly after locking, and the rate thereof decreases until stabilising; in the later stage, corrosion leads to the reduction of the cross-sectional area of the steel bar which may cause the reduction in anchorage force again. Anchorage force controls the deformation and stability of the anchored slope, the prestress loss caused by later corrosion may lead to an increased rate of displacement and stability degradation of the prestressed anchored rock slope.     

锚杆不确定性对加固边坡失稳概率的影响

为了探究锚杆不确定性对加固边坡失稳概率的影响, 建立了施加锚杆后的边坡模型, 通过以下两种途径来考虑锚杆的不确定性: 其一是假定锚杆与锚固体之间接触面上的单位表面摩擦力为对数正态分布变量, 其二是引入锚杆与锚固体之间接触面上的单位表面摩擦力衰减系数来考虑运营过程中锚杆的不确定性。采用极限平衡分析法并结合蒙特卡罗抽样法, 计算并对比分析了两种途径下锚固边坡失稳概率变化曲线, 最后以深圳假日酒店基坑边坡支护工程为例, 证明所提方法的有效性。结果表明: 对于途径一, 在相同土体统计参数下, 随着锚杆与锚固体之间接触面上单位表面摩擦力变异系数的增加, 加固边坡的失稳概率缓慢增加, 增幅介于18.03%~41.90%之间。对于途径二, 随着锚杆衰减系数自1.0逐步减小至0, 加固边坡失稳概率迅速增加, 增幅介于55.64%~124.90%之间; 在同一衰减系数下, 加固边坡失稳概率随着锚杆衰减根数的增加而增大。研究结果可以为锚杆施工与运营期间的管理提供决策支持。      

Slope reinforcement for housing in Three Gorges reservoir area

The Three Gorges Project of the Yangtze River is the largest hydropower-complex project under construction in the world. Under the largescale relocation projects, 2874 engineered slopes are formed along with the construction of new towns. In this paper, the cutting slopes are mainly soil slopes and rock slopes. Soil slopes include residual soil slopes, colluvial accumulation slopes, swelling soil slopes, and artificial earth fill slopes, etc. Rock slopes include blocky structure rock slopes, layer structure rock slopes, and clastic structure rock slopes, etc. Varied protection measures have been used for slope protection in the reservoir area including shotcrete concrete-anchor bars, frame beams, retaining walls, slope stabilizing piles, sheet-pile walls, anchorage anti-shear tunnels, flexible protection grids, and drainage, etc. Besides, slope deformation monitoring systems have been set up to monitor deformation failure and the stability state of slopes. The protection measures have guaranteed slope safety and maintained a harmony with the urban environment and surrounding landscape.     

京广铁路K1219路基土质边坡深层滑移失稳机制与整治对策

为研究土质边坡深层滑移失稳机制, 以京广铁路下行线K1219+000处路基边坡失稳为例, 通过现场调查测绘、工程地质钻探、原位试验和室内试验、深部位移监测和数值模拟等手段, 详细研究了该土质边坡变形破坏特征、地质力学过程和失稳模式。结果表明: 路基边坡表面裂缝宽度及深度呈坡顶至坡脚逐渐变浅变窄, 变形具有一定的旋转性, 牵引式特征明显, 属于深层滑移拉裂式失稳; 土质边坡经历了因坡脚开挖、抽水引起的应力场和渗流场重新分布阶段、雨水入渗软化导致下滑力不断增大而滑面逐渐迁移扩大加深阶段以及支挡结构抗力失效阶段3个地质力学过程, 其失稳模式包括浅层滑移、浅层滑面向深层迁移、动荷载触发深层滑移失稳3个阶段。在此基础上, 综合确定了滑面位置, 并通过反演方法确定了滑面力学参数。研究采用了刚架式双排抗滑桩的整治方案, 通过理论计算和数值分析, 边坡变形与抗滑桩变形基本一致, 且与监测结果整体吻合, 这表明土质边坡深层失稳理论分析准确且计算的力学参数科学, 整治对策稳妥、可靠。      

Hydro-mechanical analysis of rainfall-induced fines migration process within unsaturated soils

Seepage-induced fines migration under rainfall infiltration is a main cause leading to shallow failures in loose colluvial slopes. To describe the full process of fines migration within unsaturated soils during rainfall infiltration and the associated hydro-mechanical behaviors, a seepage-erosion-deformation coupled formulation is proposed in this paper. The governing equations proposed are implemented into a finite element code and used to investigate the influences of skeleton deformation on the rainfall infiltration process through unsaturated soil columns. The numerical results were presented in detail for a better understanding of the rainfall-induced fines migration process within unsaturated soils. Further, the obtained results are integrated into an infinite slope model for slope stability analysis. The results show that, the skeleton deformation will affect the rainfall infiltration rate and hence the timing of slope failures; meanwhile their influences are more evident if the fines deposition process is taken into account. Moreover, the slope stability could be reduced gradually due to the soil strength loss along with loss of fine particles. Therefore, particular attentions should be paid to analyzing the stability of soil slopes susceptible to internal erosion.     

基于物理模型试验的多层滑带堆积层滑坡—抗滑桩受力特征

研究抗滑桩的受力特征是进行抗滑桩设计工作的关键。我国三峡库区部分堆积层滑坡发育多层滑带,而目前抗滑桩的设计方法仅针对单层滑坡,因此,对多层滑带堆积层滑坡—抗滑桩受力特征的研究具有重要意义。基于三峡库区堆积层滑坡工程地质特征,开展了多层滑带堆积层滑坡物理试验模型,在滑坡的后缘施加推力来模拟滑坡演化过程,同时监测滑坡—抗滑桩体系的多场信息。试验结果表明,在多层滑带堆积层滑坡的演化过程中,桩身受力表现出了很好的规律性。根据坡表位移的变化趋势,将滑坡演化分为4个阶段,在此基础上对桩身受力进行分析。滑坡推力分布图式中出现了4个极大值,土体抗力分布图式中出现唯一最大值,该试验结果为抗滑桩的设计提供了一定的理论支持。      

Landslides & debris flows formation from gravelly soil surface erosion and particle losses in Jiangjia Ravine

Gravelly soils are made up of gravel, sand, silt and clay. They are widely used in engineering applications such as rock-fill dams with clay cores, which are the main researches at present. The strength and mechanical properties of the gravelly soils are affected by the content of coarse grain, fine particles, and their adhesive states. These Properties can be verified by laboratory unconsolidated undrained triaxial tests with grain size less than 5 mm and by large scale direct-shear tests with original grain content. Fine particles of the loose gravelly slopes are released under rainfalls, alternated the structures and mechanical properties, even affected the slope stability. There are a series of large scale direct-shear tests with different coarse grain contents to study the influence of fine particles releasing and migration, results showed the strength behavior of the gravelly soils were affected by the coarse grain content （5） and the inflection coarse grain contents. In order to study the erosion features of the gravelly soil slopes on rainfall conditions and the slopes stability alteration, we had carried out one sort of artificial rainfall local and model experiments, the runoff sediment contents were monitored during the experiments. Result showed that the shapes of the slopes surface transformed periodically, runoff sediment contents were divided into five phases according to the experiment phenomena, runoff sediment contents maintained downtrend during the rain time and the downtrend was obviouslyinterpreted by one descend belt no matter the rainfall intensity and the slope angels. Particle size analysis released the deposit on the slope surface lost almost all of the clay, most of the silt and sand after the experiments, this meant the fine particles releasing, migration and accumulation process on condition of rainfall resulted in the instability factor of the slopes even induced landslide or debris flow.     

Failure behavior of soil-rock mixture slopes based on centrifuge model test

The stability of soil-rock mixtures(SRMs) that widely distributed in slopes is of significant concern for slope safety evaluation and disaster prevention. The failure behavior of SRM slopes under surface loading conditions was investigated through a series of centrifuge model tests considering various volumetric gravel contents. The displacement field of the slope was determined with image-based displacement system to observe the deformation of the soil and the movement of the block during loading in the tests. The test results showed that the ultimate bearing capacity and the stiffness of SRM slopes increased evidently when the volumetric block content exceeded a threshold value. Moreover, there were more evident slips around the blocks in the SRM slope. The microscopic analysis of the block motion showed that the rotation of the blocks could aggravate the deformation localization to facilitate the development of the slip surface. The high correlation between the rotation of the key blocks and the slope failure indicated that the blocks became the dominant load-bearing medium that influenced the slope failure. The blocks in the sliding body formed a chain to bear the load and change the displacement distribution of the adjacent matrix sand through the block rotation.     

基于物理模型试验的滑坡-抗滑桩位移场变化特征

滑坡-抗滑桩体系演化机理是滑坡灾害防治的重要理论基础,其中桩土相互作用是滑坡-抗滑桩体系中的关键,而位移场是相互作用的重要表征之一,因此,对滑坡-抗滑桩体系位移场的研究具有十分重要的工程意义。以物理模型试验为手段,基于三峡库区堆积层滑坡工程地质特征,建立大型物理试验模型,通过逐级施加荷载来模拟滑坡后缘推力,采用高速摄像机及粒子图像测速技术等获取滑坡坡表与桩顶位移数据,定量分析了体系位移场变化特征。试验结果显示:在滑坡-抗滑桩体系演化过程中,坡表位移场变化呈现出很好的规律性,这为桩土相互作用研究机理起到了一定的推动作用。      

蓬莱阁丹崖山安全监测与分析

丹崖山边坡稳定性是关系古文物蓬莱阁安全的关键问题。丹崖山边坡高差大、断层裂隙发育、岩体卸荷深度大,地质条件十分复杂,边坡在施工期和运行期的稳定性问题特别突出。该文介绍了丹崖山岩体加固后的监测布置,并对岩体表面变形趋势、空间分布形态、加固后变形趋势进行分析,通过对多点位移计、锚杆测力计、锚索测力计、表面裂缝计及地表变形等监测结果进行综合分析,得到边坡岩体的变形规律。     

Numerical investigation on the initiation mechanism of debris-flow under rainfall

Rainfall is an important factor to trigger the debris flow.Numerical simulation on the responses of slopes and the initiation of debris flow under rainfall was processed by using the software FLAC2D based on the soil parameters in Weijia Gully,Beichuan County,Sichuan Province,China.The effects of the slope angle,rainfall intensity,soil parameters on the developments of the stress and pore pressure and deformation of the slope were studied.It indicates that large displacements of the slope are mainly located near the slope toe.With the increase of the rainfall intensity the stability of the slope decreases and so the debris-flow is easy to occur.     

Damage pattern recognition of spatially distributed slope damages and rainfall using optimal GIS mesh dimensions

Damage assessment for slopes using geographical information system （GIS） has been actively carried out by researchers working on several government organizations and research institutes in Korea. In this study, 596 slope damages were examined to identify the types of damage associated with dip angles, dip directions, and heavy rainfall resulting from typhoons in South Korea. Heavy rainfall of 100 mm to 300 mm resulted in 80% at the investigated slope damages. A GIS database was developed for highways, rainfall, soil or rock geometry, and types of damage. A grid of rainfall intensity was generated from the records of maximum daily rainfall. Contours for slope damages and heavy rainfall using optimal GIS mesh dimensions were generated to visualize damage patterns and show substantially strong correlation of rainfall with slope damages. The combination of remote sensing with the GIS pattern recognition process described in this work are being expanded for a new generation of emergency response and rapid decision support systems.     

基于SBAS-InSAR的矿区采空区潜在滑坡综合识别方法

针对位于山区且受大量采空区影响的边坡,利用传统测量方法监测耗费人力、物力且光学遥感难以定量识别其是否为潜在滑坡的问题,本文提出一种融合研究区小基线集（SBAS-InSAR）地表监测数据、坡度及坡向的识别方法。通过SBAS-InSAR技术获得研究区地表雷达视线（LOS）方向形变速率,将其转化为垂直方向形变速率,并根据研究区DEM建立坡度及坡向分析图,根据不同山体的坡度、坡向找到易发生滑坡的区域,融入该区域垂直方向的时序形变速率,对其进行滑坡识别。实验表明：卡房镇周边受采空区的影响较大,多数区域垂直方向年形变速率大于10 mm/a;通过本文方法对研究区潜在滑坡进行识别,发现在研究区的21处历史滑坡点中,有16处被识别为潜在滑坡,5处未被识别但也位于发生形变的区域内,表明本文方法对潜在滑坡的识别精度高,具有可行性。该研究为识别采空附近的潜在滑坡提供了一种新的思路,可以有效识别采空区附近山体边坡是否处于潜在的、不明显的滑动状态,对滑坡灾害具有预警作用。