This paper reviews the bearing characteristics and failure mechanisms of anchor plates and group anchor systems in geotechnical engineering. The study focuses on analyzing the uplift resistance and failure modes of anchor plates and understanding the group anchor effect through both experimental investigations and numerical simulations. Key findings include the significant influence of anchor plate shape, size, and embedment depth on their uplift capacity, as well as the critical role of soil density and internal friction angle. The research also highlights the interactions among anchors in group systems, emphasizing the optimal spacing, length, and diameter configurations to maximize uplift capacity. Combined experimental and numerical approaches provide comprehensive insights into the mechanical behavior of these systems, suggesting future research directions to address current limitations and explore new anchoring technologies.

Dyke breach develops rapidly, and is hard to predict and to be dealt with. Current methods of dealing with breach emergency are mainly mechanized operation and throwing materials. However, in the development of the breach, the materials are prone to be washed away due to large water head difference at the entrance and high velocity of the flow. The breach, therefore, can only be blocked after the water flow slows down, which reduces the timeliness of emergency rescue and causes great economic loss after a long time of flood inflow. We invented a flow deceleration structure based on the principle of hydraulic energy dissipation to address the problem of breach closure under high speed flow. We expounded the basic principle of flow deceleration, and verified its deceleration effect and mechanical performance via model test and numerical simulation. By using this flow deceleration method, we can reduce the difficulty of emergency rescue and make it possible to close the breach at high flow velocity.

The plate anchor is widely used because of its good bearing characteristics, but the bearing characteristics are different at different buried depths. In order to study the tensile bearing characteristics of the anchor plate, a self-developed visualized drawing device is used to conduct a drawing model test considering the influences of buried depth and drawing rate. The particle image velocimetry and the digital dynamometer are used to obtain the displacement and shear strain cloud map of packing soil and drawing load of the anchor plate. The results show that the critical buried depth ratio of the anchor plate in dense sand is around four. The drawing process of the shallow-buried anchor plate can be divided into three stages: pre-peak growth, post-peak softening and residual stability. At the pre-peak growth stage, the soil is in local shear failure state, while the soil is in the overall shear failure state at the post-peak softening and residual stability stages. The displacement and shear strain clouds are inverted trapezoidal. The drawing process of the deep-buried anchor plate can be divided into two stages: pre-peak growth stage and post-peak fluctuation stage. In this case, the soil is always in local shear failure, the displacement cloud is in bubble shape distribution, and the shear plane is always in the width of three times of the anchor plate above the anchor plate. The relationship between the dimensionless load and the dimensionless displacement is hyperbolic. This relationship is given and compared with other research results. The shape coefficient-modified Giampa formula can predict the bearing capacity coefficient of the anchor plate well.

Taking a 25 m-high expansive soil temporary channel slope as the research object, through the field channel tests on sliding channel slope, long and large cracks are found at the left and right banks of the channel in the elevation between 140~142 m, and the slope instability is under the control of crack strength. According to the position and shape of the slip surface, a representative channel section is selected to carry out the design of the prestressed umbrella anchor reinforcement scheme, and a complete monitoring section with anchor force and deformation as the main monitoring means is arranged. Aiming at the low accuracy of the existing soil slope anchor force monitoring, an indoor physical model test is carried out to study the applicability of the prestressed umbrella anchors for soil slope monitoring. According to the results of the in-situ monitoring and model tests, the stable states of the canal slope during the processes of excavation, reinforcement and rainfall are analyzed. The key factors affecting the stability of the canal slope and the rationality of the canal slope reinforcement scheme are clarified. The criterion for stability state judgment of high expansive soil slopes are put forward based on the anchor force monitoring.

The umbrella-shaped bolt (U-bolt) is a novel type of mechanical bolt used for rock reinforcement. It is made of a smooth steel bar, hinges, rigid rods, and sliding blocks. During installation and operation, the tension of the bolt is converted into the extrusion force on the rock mass deep in slope, so that the higher compressive strength of the rock mass is used to obtain the greater friction force and anchoring force. In this article, the structural and mechanical analysis results of the U-bolt is provided, and the relation between penetration and point normal stress is discussed. Based on these analyses, a simulation method for the U-bolt is proposed. The bolt elements are identified at first, then the penetration on the rock mass is calculated, and the tensile strength of bolt elements is increased to a reasonable value. Meanwhile, the method is applied to deep-buried rock reinforcement and a rock slope, and simulation results reveal that the U-bolt can alleviate the fracturing degree and reduce the depth and displacement of the excavation damaged zone (EDZ), and decrease the landslide distance.

The existing reinforcement technology of rock slope and cavern cannot provide large anchoring force and high time efficiency at the same time, which leads to being unable to achieve rapid and effective prevention and rescue in case of landslide, collapse and other dangerous situations. As a new type of mechanical anchoring bolt, rock umbrella anchor is based on the principle of compressing rock mass by tensioning the metal wedge and then producing friction force, finally using the compressive strength of rock mass and interface action to obtain large enough anchoring force. The new anchor can adapt to the deformation of the rock mass, realize rapid anchorage, and obtain larger anchoring force while continuously tensioning. In this paper, the structure composition of rock umbrella anchor is introduced at first. Secondly, based on the geometric characteristics of the structure composition, the anchoring mechanism is analysed and supposed. Thirdly, in-door pull-out model test is conducted to study the structural and anchorage performance of the rock umbrella anchor. In the tests, the deformation characteristics of the anchor are recorded and analysed in the whole pull-out process. Meanwhile, the anchorage failure modes, failure mechanism together with corresponding bearing capacity are obtained, and the influence factors are analysed. Finally, the supposed anchorage mechanism has been verified and the suggestion for application of this new type of anchor is proposed. The results of this paper provide experimental support for the design and engineering application of rock umbrella anchor.

Deep buried sand is a granular structure system, and accurate determination of its original mechanical properties is a difficult problem in geotechnical engineering. Pressure meter test (PMT) is an ideal in-situ deep-seated testing method for deep buried sand, but there is a lack of quantitative evaluation criteria for the depth effect. In order to solve the problem of depth effect of PMT, a self-developed physical model testing system was applied to simulate the stress state of deep buried sand. By applying different overburden pressures P-0' to simulate the PMT at different depths, the variation rules of PMT modulus E-M and PMT plastic pressure P-f as a function of overburden pressure P-0' are obtained, and a method is suggested to revise the characteristic value of the bearing capacity of foundation f(ak) based on the PMT plastic pressure P-f. The test results show that the depth effect does exist in the PMT. With the increase of test depth, the burial overburden pressure P-0' increases, and the change of EM is not obvious. Also, P-f is linearly correlated with P-0'. This study provides reference and basis for the determination of physical and mechanical properties of deep buried sand.

2020年鄱阳湖水位突破1998年历史极值,多处圩堤发生险情,险情数量多、种类繁、危害大,对现有应急抢险技术提出了严峻的挑战.以鄱阳湖圩堤防汛抢险实践为基础,首先综合介绍了鄱阳湖圩堤出险及抢险的整体情况,然后针对圩堤发生的典型管涌、散浸、漏洞、漫溢、脱坡、溃口等险情抢险方法进行分析总结,归纳现有应急抢险技术的优势与不足,最后综合考虑汛前防御和汛后重建的要求,提出应急抢险技术的发展方向.相关结论可为防汛应急抢险提供智能便捷高效的研究思路和方法.

The technology of blocking dyke burst has been developing gradually due to frequent dyke bursts in histo-ry. However, the blocking technology needs to develop towards modernization due to low efficiency, high depend-ency on manual power, and low degree of mechanization. In this paper, we made a review on the studies and prac-tices of dyke burst and obtained some conclusions: the discharge and flow velocity at dyke breach can be deduced according to the shape and width of breach as well as the water depths on both sides of the dyke. The shape and width of the breach is determined by water head and affected by discharge of river channel and filling material of dyke. In spite of differences in emergency rescue technologies corresponding to different watersheds, the core prin-ciple is to dumping materials step by step and reduce flow velocity gradually. The key to successful blocking is to ensure the anti-scouring stability of dumping materials, which can be enhanced effectively by anti-scouring struc-ture. In addition, light and convenient modern rescue equipment is also a critical approach to improving blocking efficiency.

Expansive soil stratum is featured with deep fissure development which brings about stability problems to high slope of expansive soil in excavation process. Commonly used reinforcement or protective measures for tempora-ry high slope of expansive soil are of poor adaptability and low economic benefit. Prestressed umbrella-shaped an-chor is a new solution for the reinforcement of temporary expansive soil slope. In order to solve the stability problem in the excavation of expansive soil slope in Water Resources Allocation Project in North Hubei Province, we con-ducted field test of prestressed umbrella-shaped anchor and evaluated its popularization value in practical applica-tion. Research result demonstrates that prestressed umbrella-shaped anchor is of fast construction and large resist-ance against pull-out force, hence effectively controlling deformation development and ensuring slope stability. Ac-cording to the safety monitoring data of slope, we verified that umbrella-shaped anchor is of good application and popularization values in the rapid reinforcement of expansive soil slope.

Due to the complex environment of oceans, present in-situ test methods are of some limitations in obtai-ning the physical and mechanical properties of undisturbed soil in offshore engineering applications. A novel pull-out cone penetration test ( CPT) is proposed to solve the problems. In order to verify the feasibility of this method, we conducted CPT, pressuremeter test, and pull-out CPT and compared the curves of test parameters against depth as in different in -situ test methods. We found that the test result obtained by the pull-out CPT was of similar varia-tion trends with those of other test methods, implying that pull-out resistance is able to reflect soil’s physical and mechanical properties, and that the proposed pull-out CPT is feasible. The research results lay the foundation for further research and application of pull-out CPT.

Drainage system and pressure reduction measures are usually adopted to treat the uplift of anti-seepage structure of water transfer project caused by long route and varying groundwater table.Check valve-drainage system in which reverse check valve plays a key role nakes one of the best choice for its one-way flow performance.Existing reverse check valves have an inflexible opening and shutoff process,a poor long term performance,a meticulous construction operation,and must be accurately installed in a certain direction.To solve these problems,a novel reverse check valve based on differential pressure amplification is researched and developed in consideration of application conditions.The principle of opening and shutoff is improved;and new shutoff type and anti-clogging method are put forward.Opening and shutoff of the new check valve is only driven by amplified differential water pressure,and no other external force is needed,thus,it can be installed in every direction.Differential pressure amplification components and arc close structure are developed to improve the reliability and flexibility of opening and shutoff.Anti-clogging structure is designed and anti-fatigue problem is considered to ensure the long-term performance.The new reverse check valve can be widely used in the drainage system of canal,slope protection of dike and river course,groundwater table change belt of dam,water conveyance tunnel and other water-involving structures.

According to the failure mode of expansive soil slope induced by expansion effect and the monitoring re?sult of on?site simulation test, we summarize the techniques of expansive soil slope treatment. Furthermore, we compare and analyse the effectiveness of four treatment measures ( cement soil modification, geogrid reinforcement, geomembrane, and geotextile bags filling) by evaluating the slope deformation and the variation of moisture content. Results reveal that cement soil ( replacement of non?expansive clayey soil) has the best performance, whereas geo?grid reinforcement is featured with complex techniques, and the compaction degree of geotextile bags filling is hard to control. Finally, we put forward the principles of expansive soil slope treatment.

In order to realize the scientific and reasonable design and construction of composite foundation of grid?shaped CDM( cement deep mixing) piles with high?replacement rate in sand foundation, we carried out the static load tests on the composite foundation of grid?shaped CDM piles, Xinglong hydro?junction in Hanjiang River basin in Hubei provinceis taken as example. Result shows that 1) the P?ΔS/ΔP ( pressure vs. variation rate of settlement with pressure) curve of CDM piles can be divided into three sections, that is, the line segment of pile shaft resist?ance, the adjustment and change section of pile tip resistance and the failure section of pile tip resistance. 2) The curve of P?ΔS/ΔPcould better reflect the rigid variation and working behavior of the composite foundation of CDM piles than the curve of P?S(pressure vs. settlement). Moreover, the pile shaft resistance can be fully developed, which has mouth?shaped layout with high?replacement rate in sand foundation. The piles in grid shape are typical frictional end bearing piles as the limit bearing capacity of pile is mainly affected by the residual strength of bottom sandy soil in compacted state after shear failure.

目前关于格栅状搅拌桩复合地基工作性状的研究工作相对较少,对其变形机理不甚了解.在兴隆水利枢纽格栅状搅拌桩复合地基现场载荷试验成果的基础上,考虑桩-土之间的相互接触,建立考虑搅拌桩-土共同作用的三维有限元模型,数值模拟复合地基群桩现场试验的实际加载过程.通过对比口字型群桩试验与数值模拟的P-S曲线,验证了数值方法及参数取值的正确性;分析了桩身轴力、桩间土的竖向应力及桩侧摩阻力等变化规律,研究了桩体与土体的荷载分担过程关系,获得桩身轴力及摩阻力分布规律;根据竖向平衡方程,推导得到平均桩端阻力和侧阻力,研究可为工程设计提供参考.

压实度是渠道填筑工程质量控制的重要指标,通常采用环刀法进行检测,但存在检测周期长、开挖扰动大等不足;基于可变能量动力触探仪所测锥尖阻力与压实度具有较好相关性的原理,提出了一种压实度快速检测方法;即采用传统环刀法对拟检测区域进行标定,获得对应压实度合格线的锥尖阻力,测定筑填体的动力触探曲线,根据锥尖阻力评价填筑体质量;该方法对填筑体损伤很小,且实现了多层连续快速测试,满足检测的需求,具有广阔的应用前景.

For many high rockfill dams, which are constructed or will be constructed in Southwest China, deep overburden is one of the most complex engineering problems. The deformation and stress status play an important role in the safety of dams. For the traditional methods, because it’s almost impossible to collect gravel overburden layer samples, the original density cannot be determined exactly. Thus, it is very difficult to get the reliable mechanical and seepage properties of overburden layer in laboratory tests. A new method that indirectly calculates the original density of overburden gravel using pressuremeter tests (PMT) or dynamic penetration tests (DPT) is proposed. In the construction period of Wudongde, this method is successfully applied to the determination of the density of overburden layer. Furthermore, based on the indoor model tests, it is verified that the correction factor of rod length in DPT follows the description of Newton elastic collision theory. Therefore, a new pressuremeter probe with high pressure and side expansion is developed in order to conduct the whole-process pressuremeter tests on deep overburden. The proposed whole set method provides an important technical support for further studies on the engineering properties of deep overburden of dam foundation.

In order to ensure the anti-floating stability of concrete linings and to prevent water infiltration, the drainage system with the function that meets the requirements of both seepage control and drainage is widely needed in water conservancy projects. One of the choices is the reverse check valve. As a new product, the reverse check valve is not widely used, neither its performance nor method is available, which brings a certain risks to projects. The closed head, open head and drainage quantity are put forward based on the engineering requirements and work principles as the common indices for the reverse check valve. The test equipment and method are developed for the reverse check valve. The long-term performance of the reverse check valve is analyzed. The research findings may provide reference for the tests on the reverse check valve.

A series of large-scale static model tests of compacted expansive soil slope were conducted with real-time monitoring of water content, swelling deformation, and soil pressure. The monitoring results suggested that the distribution of water content in the slope was nonuniform in space and time, thus resulting in the nonuniform distribution of swelling deformation at the drying-wetting interface. According to the survey of failure surface by excavation after landslide, it could be observed that, local shear rupture firstly took place at the drying-wetting interface within the shallow layer of slope, and then extended downwards gradually as water infiltrates downwards, multiple shear sliding surfaces were produced at different depths and different areas and they were further connected with each other. Eventually, an overall landslide of the slope occurred. Traditional limit equilibrium method could not correctly reflect the progressive landslide of expansive soil slope. Finite Element Method with expansive model was adopted and the safety factor of the static model test slope was calculated as 0.92 using strength reduction technique. Both physical model tests and finite element analysis prove that the swelling deformation plays an important role in expansive soil slope stability when over-consolidation effect and fissure presence are not considered.

Before building a dam in a river,cofferdams are needed to be constructed in advance.The most commonly used method of filling a cofferdam is to dump granular materials into the deep water and let the particles pack together by gravity.Granular materials such as sand,sandy gravel and ballast are often used as the main packing materials,and the density formed by underwater packing of granular material is the key parameter for cofferdam design.Since the density cannot be obtained directly by sampling or calculation owing to the lack of theoretical or empirical solution,it has become an unsolved problem in the design and construction of cofferdam.In view of this,through analyzing the density's influencing factors we conducted centrifugal model tests on 3 typical granular materials(sand,sandy gravel,and ballast) to measure the densities under different conditions,and investigated the influences of particle figuration,size and gradation on the density.On the basis of the test data,some insights about the particle packing underwater are summarized,and a tentative formula to estimate the particle aggregate density is proposed.