The ultimate uplift capacity of multi-underreamed anchors (MUAs), a key design parameter in anchor engineering, is influenced by the parameters of the surrounding soil, anchor, and anchor–soil interface. To explore the ultimate uplift capacity of MUAs in soft soil, this study establishes mechanical models of the arch-shaped and cylindrical failure modes of MUAs. These two mechanical models follow a series of basic assumptions. The formulas for calculating the bearing capacities of MUAs in the two failure modes are then derived based on the equilibrium balance theory. The methodology to derive the ultimate uplift capacity of MUAs proposed here is in close agreement with model test data. The ultimate capacity of MUAs comprises the end and side bearing capacities. Because of the superposition of the side and end resistance effects, the ultimate capacities of MUAs are higher than those of non-underreamed anchors. The arch-shaped and cylindrical failure modes of MUAs can influence each other via a variety of underream parameters. With increasing relative underream parameters, the ultimate uplift capacities of MUAs with arch-shaped and cylindrical failure modes both increase, linearly or nonlinearly.

Horizontal drains have been widely installed along expansive soil slopes to maintain slope stability. However, these drains typically get clogged with clay particles after several years of operation and must be maintained and replaced regularly. This paper proposes a new type of horizontal drain with a replaceable tubular filter element (RTFE) to overcome the time-consuming nature and laborious replacement procedure of existing horizontal drains. Tests were conducted to compare its drainage performance with that of a conventional horizontal drain. The effects of horizontal drain clogging on the pore water pressure and slope stability were analyzed using the equivalent permeability coefficient of the expansive soil considering the adverse effects of cracks that are randomly distributed in the soil when the matrix suction exceeds the air-entry value. This coefficient was then used as one of the input parameters in the finite element analysis (FEA) for a hydro-mechanical coupling simulation. A replacement standard for the tubular filter element was established according to the numerical results, and the replacement method was explained. The study results showed that the RTFE-equipped horizontal drain was evidently superior to the conventional horizontal drain owing to the advantage of quick replacement. It can also effectively preserve the soil and prevent infiltration deformation caused by the loss of skeleton particles, implying a more economical, effective, and controllable means for the dewatering of expansive soil slopes. This study provides references for the construction and management of engineering projects involving horizontal drainage systems.

基于2022年9月5日泸定MS6.8地震的野外调查,结合遥感解译结果,总结了泸定地震同震地质灾害的发育特征和主控因素,研判了同震地质灾害的演化趋势,并针对同震地质灾害防灾减灾的不同阶段给出了相应的建议.结果显示:泸定地震同震地质灾害整体以小?中型崩塌、滑坡为主,集中分布在磨西镇和海螺沟、得妥镇湾东村、得妥镇大渡河沿岸三个区域;主震和余震、鲜水河活动断裂、地形地貌、特殊岩土体是泸定地震同震崩滑空间分布的主控因素;泸定地震震后地质灾害在未来十年内会极为活跃,需要密切关注磨西河和支沟、大渡河河谷两侧的高陡岸坡、大渡河高阶地、磨西台地边缘区域以及磨西镇、得妥镇同震崩滑密集发育的泥石流沟谷.根据同震地质灾害应急防范的管理逻辑,建议地方政府按照过渡性安置详查阶段、恢复重建阶段、长远规划阶段三个阶段来针对性地开展地质灾害的防灾减灾工作.

采用双掺氯乙烯-乙烯-乙烯醚乳液(PTB乳液)与橡胶颗粒对水泥砂浆进行改性,通过正交试验研究了不同聚灰比、水灰比及减水剂、橡胶颗粒掺量对水泥砂浆抗折强度、抗压强度、折压比、黏结强度和抗渗性的影响.结果表明:抗折强度与抗压强度随聚灰比、水灰比及减水剂、橡胶颗粒掺量变化而变化的规律较为一致,而折压比随着橡胶颗粒的增加而增加,但随着聚灰比、水灰比及减水剂掺量的增加而先增加后减小;黏结强度随聚灰比及水灰比的增加而降低,随减水剂的增加而增加,而随橡胶颗粒含量的变化无明显变化规律;橡胶颗粒的掺入,使砂浆抗渗性明显降低,而少量的PTB乳液即可明显改善其抗渗性.

Expansive soils are widely distributed in China, especially in the regions with high population density. Characterized by the well-known 'three properties', i.e., swelling-shrinkage, cracking and over-consolidation, the expansive soils are highly susceptible to climate change and engineering activities, and thus can easily cause landslides. Due to the lack of consideration to the interactive 'three properties' of the expansive soils, the traditional techniques can hardly be effective for the treatment of expansive soil landslides and engineering slopes, leaving the latter known as 'cancer' that imperils the safety of engineering projects. During the 13th Five-Year Plan period, the National Key Research and Development Program of China "New prevention and treatment techniques and their applications to landslides and engineering slopes of expansive soils" was approved. With special attention to the interactive 'three properties' of the expansive soils, the program has made series of innovations including the instability mechanism and the key disaster factors of expansive soil landslides, multi-field information monitoring and early warning techniques, 'surface-shallow-deep' integrated and ecological reinforcement technique, health diagnosis and rapid restoration techniques for slope protection structures. These techniques are integrated as a technical system and have been implemented in three engineering demonstrations. The relevant achievements have provided new theories, techniques and construction methods for treating the landslides and engineering slopes of the expansive soils. Meanwhile, they have achieved significant social, economic and environmental benefits, with broad application prospects.

本文以藏东南地区帕隆藏布流域冰碛物斜坡为例,针对其架空结构较多、固结程度欠佳的特点,提出钢花管注浆加固技术.通过15个注浆孔现场注浆、现场开挖、取样测试等,探讨其施工工艺及加固效果,并结合FLAC3D数值模拟,进一步阐明其加固机理及设计方法.研究结果表明,冰碛物浅表层注浆有效加固半径为20～55 cm,浆液扩展路径与架空结构展布息息相关;注浆加固后土体粘聚力、内摩擦角、压缩模量均得到改善,竖直渗透系数变小;其注浆压力宜采用0.5～1.0 MPa;水灰比宜选用2、1;注浆孔间距与有效加固半径的比值不宜大于8.通过现场试验,形成一套基于3.5 m3空压机、YT28型凿岩机、空心自钻式锚杆及气动式注浆机的花管注浆工艺,轻便快捷,施工效率高,尤其适用于交通不便、施工条件差的情形.

The planned grand bridge is an important control bridge along the Sichuan-Tibet Railway. A large- scale bedding rock collapse occurred on the slope of the Baqu river side of Chengdu bank, with the protruding ridge, high elevation difference, complex and changeable lithology, poor rock mass structure and integrity, highly weathering and unloading and potential unstable rock mass on the surface of the slope. This paper investigates the topography and geomorphology, stratum lithology, discontinuities development and the characteristics of deformation and failure of the bank slope to Chengdu by remote sensing interpretation, profile measurement and stability calculation. The stability of bedding rock slope of the Baqu river side of Chengdu bank under natural and rainstorm conditions are analyzed and evaluated. The results show that the safety factor of slope stability is greater than 1.1; under the strong earthquake (PGA>0.3 g) conditions, the safety factor of slope stability is less than 1.0, and local or overall instability may occur. Based on removing the dangerous rock mass on the surface of the slope, it is suggested that the possible failure range and degree of the bedding rock slope on the Baqu river side should be further studied and the engineering prevention measures should be put forward.

为了研究2017年“8·8”九寨沟地震对景区泥石流治理工程的影响,利用野外调查、采样测试和对比分析等手段,基于泥石流治理工程损毁的时序、分布及表观特征,分析工程震损类型和机制,提出防治建议和修复对策.结果 表明:(1)单体治理工程震损程度分为完好、轻微、较重、严重和损毁5级,占比分别为30％,43％,12％,9％和6％,单沟治理体系震损程度可分为系统性损毁、局部损毁和轻微损毁,占比分别为4.76％,57.14％和38.10％;(2)基于震损与地震的相对时序关系,有直接震害和震后间接损毁2种方式,前者包括震裂破坏和同震灾害破坏,主要受地形条件和工程结构尺寸约束,后者有冲击破坏、磨蚀破坏、绕流破坏等,主要受控于灾害物理特性和动力特征的演化;(3)地震影响最大的间接损毁是多要素耦合作用结果,具有“多因同症”的特点,主要驱动力为流量、流速、容重和漂木含量;(4)震后泥石流治理中,需适当增大动力参数,优化关键结构,预留安全储备,损毁工程的修复需同时满足最小地表扰动和景观保护需求,可采取非开挖加固和功能改造等手段.

Moziyan is an area containing unstable rock masses located in Hechuan District, Chongqing, China and has constantly seen group-occurring rockfalls since 1964. The present study aims to investigate the damage of Moziyan rock mass and protect the mining areas and residential areas from rockfall phenomenon. Mohr–Coulomb model in FLAC–3D Program was built to find out the rockfall initiation position. RocFall program has been used to calculate the distribution curves of stopping positions, bounce height, total kinetic energy, and translational velocity of the falling blocks varying with horizontal distance. According to the simulation results, the stability of Moziyan rock mass is controlled by the unloading cracks behind the slope, and the falling blocks have a maximum bounce height and maximum total kinetic energy of 0 m and 2720.9 kJ respectively at the horizontal position of 461.6 m, where proper protection measures should be adopted to minimize the risk of the damage of the Moziyan rock mass. Conclusively, the results of simulation indicate that a barrier of 3 m height and 3000 kJ absorption capacity is enough to resist the falling stones with a maximum speed of 13.2 m/s at the horizontal position of 461.6 m.

为了探索爆破参数对直立岩层边坡岩体的静态爆破影响效果,通过电测法测试了钢管试件中静态破碎剂产生的静态膨胀压,设计了考虑抵抗线、孔距、水平压力、布设方式等参数的静态爆破试验.试验结果得出:在径向约束条件下,静态破碎剂产生的膨胀压力随时间成指数增长趋势;在水平约束条件下,水平约束力越大,岩体开裂所需要的膨胀压越大,直立岩层岩体的残余水平构造应力是静态爆破设计的关键参数;钻孔裂纹贯通时间随孔距非线性增大,建议静态爆破设计孔距为2～2.5倍钻孔直径.进一步讨论得出:三角形布设方式的爆破效果明显优于矩形布设方式,直立岩层边坡岩体的静态爆破过程可分为岩体微裂、孔边裂纹扩展、裂纹密集发育和岩体碎裂4个阶段.

为了验证锚索预应力修复加固变形抗滑桩机制,在大型野外模型试验的基础上,对模型试验进行了数值分析.数值分析结果表明,数值模拟与模型试验结果较为吻合,预应力锚索的施加可有效控制变形抗滑桩桩顶位移,降低桩身弯矩,提高抗滑桩承载能力,从而达到加固变形抗滑桩的目的,验证了锚索预应力修复加固变形抗滑桩机制.讨论结果表明:采用锚索预应力修复加固变形抗滑桩存在预应力上限值,此上限值随滑坡推力的增加三次抛物线降低,随桩顶位移的增大负指数降低,随距桩顶位置增加近似线性降低;在滑坡推力作用下,桩后土压力为正三角形分布,在预应力锚索修复荷载作用下,呈现为折线型分布.研究成果对于变形抗滑桩的修复加固工程设计具有指导意义.

Scouring below the check dam is a doomed consequence after the upstream reservoir is fully deposited by debris. With the boulders crashing and debris flow scouring, apron, auxiliary dam or submerged dike which is commonly used as an erosion-control below the dam is gradually damaged. In the meantime, a scoured pit is formed and expanded, causing exacerbated headward erosion to the foundation of the dam, and easily inducing a toppling failure to the dam. In order to solve this problem, this paper puts forward an application of small caliber steel pipe piles to reinforce the foundation of check dam and prevent it from scouring by debris flow. The principle is that the small caliber steel pipe piles are embedded in the debris deposit at the front side of the dam toe, and the cement slurry is also injected into the pipe piles, to penetrate into the loose debris between the piles and bond the pipe piles and the debris deposit together. Through these steps, a consolidation body with a stronger anti-scour ability is formed, preventing the dam foundation from the headward erosion by debris flow and ensuring its safe running. By means of theoretical analysis and laboratory test, 4 key parameters of embedding location, pile depth, spacing between piles and layout arrangement are determined for the technical method design. Finally, an engineering project is carried out in the Yongjiagou debris flow valley in Mianzhu City, validating that this technical method has a good reinforcing effect. It is hoped that this will provide a reference for the erosion-control design for check dams in the future or for the rehabilitation and reinforcement in the maintenance stage.

通过开展植筋技术用于格梁缺陷加固的模型试验研究,分析了植筋技术加固前后格梁随着荷载的增加,内力和弯矩的变化情况,结果表明:滑坡推力作用在植筋层和格梁复合体上时,二者并不是同时受力,植筋层先于格梁受力,植筋层所承受的荷载分担比约为78％;经过植筋技术加固缺陷格梁后,配筋受力得到改善,加固后配筋最大应力比加固前降低了36.5％;植筋技术加固后缺陷格梁弯矩明显降低,为加固前的20％～30％,说明植筋技术加固缺陷格梁效果显著.

抗滑桩承受荷载的过程伴随着桩身结构的损伤累积,为了获得抗滑桩损伤演化情况,基于Najar损伤理论推导了随应变变化的损伤因子表达式,建立了抗滑桩受拉、压荷载作用下的混凝土损伤模型.将该损伤模型嵌入至Abaqus/CAE模拟程序自带的混凝土塑性损伤模型中,分析了二郎山1#滑坡抗滑桩损伤情况,得出如下结论,采用文中构建的拉、压损伤模型模拟得出的桩顶水平位移为30.3cm,与现场观测的桩后裂缝宽度数据相吻合,得出滑坡推力增大是导致二郎山1#滑坡抗滑桩产生大变形的直接原因;抗滑桩在产生大位移过程中受压损伤值较小,桩身未发生压破坏;抗滑桩在产生大位移过程中靠近滑坡一侧滑面位置的拉损伤较为严重,并产生了拉破坏,损伤区域达到截面面积的3/4,是抗滑桩工程修复亟需关注的位置.

针对川东红层滑坡典型易发区域,采用小基线集(SBAS)时间序列的InSAR(interferometry synthetic aperture radar)方法进行了解译,并采用Google Earth可视化展示,有效圈定并复核了潜在隐患区域.提取了采矿引起斜坡失稳及牛马场滑坡的变形位移曲线,揭示了其变形规律.研究结果表明:解译区滑坡基本都发育在形变速率较大的黄色欠稳定和红色不稳定区域,区域形变位移值大小与滑坡发育比例成正比关系,35％的解译面积滑坡发育比率可以达到70％以上.同时通过野外调查发现4个潜在不稳定隐患斜坡,极大地提高了红层滑坡的早期识别能力.InSAR解译显示研究区西北区由采矿引起的斜坡失稳,与干涉图上的条纹位置对应较为一致,形变位移最大能达到视线向20 mm/a;牛马场滑坡范围均为垂直形变速率较大的黄色和红色解译点,变形位移曲线显示滑坡发生前已经处于蠕变变形阶段,累计变形量可以达到500 mm左右.

施加预应力锚索是修复含微裂纹抗滑桩最重要的手段之一.为了探讨施加预应力锚索修复含微裂纹抗滑桩的可行性以及修复过程中抗滑桩变形破坏特征,采用大型物理模型试验对预应力锚索修复含微裂纹抗滑桩进行了研究.试验结果表明,施加预应力锚索修复含微裂纹抗滑桩可提高抗滑桩承载储备能力;滑坡荷载-桩顶位移曲线可分为挤密、线弹性变形与破坏3个阶段;滑坡荷载下桩体在滑面附近位置发生破坏,破坏具有突发性;预应力荷载下抗滑桩在锚索孔位置产生拉破坏,并伴随滑面位置裂纹的扩展;滑坡荷载下桩后土压力呈三角形分布,施加预应力荷载后土压力呈倒梯形分布;锚索预应力的施加降低了弯矩峰值,但最大弯矩位置向锚索孔位置以及滑面附近位置转移,该2处位置是采用预应力锚索修复抗滑桩的薄弱部位.研究成果对于预应力锚索修复含微裂纹抗滑桩技术的推广应用以及抗滑桩修复工程的设计具有指导意义.

V型排导槽是一种有利于泥石流固体物质排泄的速流结构形式,可解决泥石流在槽内发生淤积堵塞的难题,因而被广泛应用.但是,因V型排导槽流速计算中水力坡度采用相同权重横纵坡矢量合成的综合比降,导致排导槽流速计算结果不准确而仍发生泥石流淤积的现象,不能充分发挥V型排导槽的速流优势.为了揭示V型排导槽横纵比降对泥石流流速的差异影响,设计完成了25组室内模型实验,分析了不同横纵比降组合条件下泥石流流速的差异及原因,查明横纵比降均与泥石流流速呈正相关关系,其中横比降对泥石流流速的影响低于纵比降;根据实验数据建立了泥石流流速关系式,得到横比降和纵比降在V型排导槽泥石流流速中的权重分别为0.75和1.30,验证了横比降在V型排导槽综合比降中的权重影响低于纵比降,为V型排导槽过流能力计算的优化研究提供思路和参考.

施加预应力锚索是修复大变形抗滑桩工程常用的技术之一,而锚索预应力的计算是修复工程设计的关键.基于弹性桩基本理论定义“大变形抗滑桩”概念,界定抗滑桩修复工程中锚索预应力上、下限值对应的桩顶位移状态;以修复上、下限状态的桩顶位移为设计目标,将抗滑桩自由段假定为悬臂梁,嵌固段假定为弹性地基梁,利用桩-索位移变形协调条件,分别推导锚索预应力上、下限值表达式,并将所提计算方法应用于预应力锚索修复大变形抗滑桩模型试验.结果 表明:采用所提计算方法与模型试验获得的锚索预应力上、下限值误差仅6％,施加预应力锚索改善了大变形抗滑桩桩身受力性能,修复效果较好,验证了此方法的合理性.现场工程应用表明:某特大滑坡大变形抗滑桩桩顶位移得到有效遏制,抗滑桩工程处于稳定状态,进一步印证了所提方法的正确性.

针对目前预应力锚索修复抗滑挡墙缺陷理论研究落后于实践的现状,基于野外大型物理模拟试验,监测修复全过程中的位移、土压力及预应力变化,探索预应力锚索、抗滑挡墙及土体相互作用机制.试验表明,当挡墙整体倾斜时,土压力沿墙身呈三角形分布;施加预应力修复时,土压力在锚点附近变化较快;二次加载过程中,预应力锚索从预应力损失过程到被动受力过程,发挥修复加固的作用,整个模型不产生较大变形.通过假定挡墙倾斜土压力分布形式,推导了抗滑挡墙倾斜时的土压力计算公式,建立了预应力锚索修复抗滑挡墙缺陷设计流程及力学设计方法;并探讨了数值计算方法.

为解决抗滑短桩加固滑坡体理论研究不满足工程应用需要的现状,本文采用基于快速拉格朗日算法的FLAC3D软件,对桩长变化的抗滑短桩加固碎石土滑坡全过程进行三维有限元模拟,通过分析滑体位移、应力、抗滑短桩位移和桩身弯矩的变化规律,研究抗滑短桩的受力变形特性及桩土相互作用机理.研究表明:经抗滑短桩加固后的滑坡,稳定性显著提高;随着桩长增加,桩后应力分布越均匀,抗滑短桩与桩周土体的整体性越好,滑体最大位移逐渐减小,有效抑制滑体位移;当桩长小于60 cm时,滑体出现"越顶"现象,在楔形体前缘顶部形成了贯通滑动面,且发生较小范围的失稳破坏;当桩体自由段与滑体厚度比值为0.52～0.59时,加固效果最理想.研究结果对抗滑短桩加固滑坡体的抗滑机理予以补充.