Block Revetments Research Articles

Articulated Concrete Block Stability Assessment for Embankment-Overtopping Conditions

AbstractArticulated concrete block (ACB) revetment systems are widely used for channel lining and embankment protection. Current approaches for prediction of ACB system stability use a moment stability analysis with a ratio of the boundary shear stress to critical shear stress to account for all hydrodynamic forces, which results in the exclusion of the flow velocity. Two embankment-overtopping laboratory data sets for a given ACB system were initially evaluated using the current industry-accepted design method. A new stability analysis method, termed the shear and velocity stability assessment method, was developed for ACB systems with embankment-overtopping flow, which uses a moment stability analysis in which hydrodynamic forces are computed using both boundary shear stress and flow velocity. A database was developed that included overtopping tests for three ACB systems with varying embankment slopes and lengths. The current design methodology accurately predicted stability for 67% of the tests and the...

무독성 호안블록의 수리학적 안정성에 관한 실험적 연구

본 연구의 목적은 국내 하천 복원의 자연친화적인 설계를 위한 무독성 호안공법의 수리적 안정성을 검토하는 것이다. 최근 들어 공학적 효율 위주의 치수 기능만을 위한 하천관리 정책에서 벗어나 하천의 환경적 기능의 개선을 위한 생태하천 복원사업이 이루어지고 있다. 그러나 신규 호안공법에 대한 부적절한 수리학적 설계기준이 자주 홍수기 경제적 손실을 유발하고 있다. 사석 및 블록의 안정성에 관한 연구는 크게 하천에서 제방, 하상보호, 세굴방지 등의 목적과 바다에서 호안 또는 방조제의 축조에 따라 투하하는 사석의 안정성에 기초를 둔 연구가 대부분이며 경험식으로 이루어져 있다. 본 연구에서는 최고 유속 3.5 m/s인 고속수로를 제작하여 수리실험을 수행하였으며, 무독성 접착제를 이용한 블록공법에 대한 다양한 조건의 수리실험을 통해서 수리적 안정성을 위한 호안블록의 한계유속을 구하였다. The purpose of this study is to examine the hydraulic stability of non-toxic revetment technique for eco-friendly design of the domestic river restoration. Recently, instead of the flood control function-oriented river management policy for the engineering efficiency, the improvement of the environmental performance for the ecological river restoration project is implemented. However, the inappropriate hydraulic design criteria of the new revetment technique happen to the economic losses at flood season frequently. The hydraulic stability of the riprap and the block include the banks of rivers, riverbed protection, scour protection and so on. In this study, the high speed experimental channel was developed, which has the maximum velocity of 3.5 m/s, to perform the hydraulic experiments of the block method with non-toxic glue with various conditions to find the critical velocity of the revetment block for the hydraulic stability.

식생강화를 위한 다공성 소일 블록의 치수안정성 해석

본 연구에서는 자연친화적인 호안 블록의 현장 적용시 충분한 기술적인 검증과 구조적, 수리학적 안정성 검토 등이 제대로 이루어지지 않고 있는 문제점을 개선하기 위해 생태적 기능을 확보할 수 있는 식생강화를 위한 다공성 소일 블록에 대하여 수리적 거동 변화에 따른 수리학적 안정성을 검토하였다. 대상구간을 선정하여 수치해석 및 수리모형실험을 실시하였으며 수치해석을 위해 1차원 수치해석모형인 HEC-RAS와 2차원 수치해석모형인 RMA-2를 이용하여 1, 2차원 수치해석을 실시하였고, Froude 상사법칙을 적용하여 식생 유, 무에 따른 축척된 수리모형실험을 실시하였다. 수리모형실험의 경우 실험결과에 대한 타당성을 위해 축척된 수리모형실험의 유속 및 소류력 결과를 원형으로 환산하여 1, 2차원 수치해석결과와 동일한 조건하에 비교 검토하였고 그 결과 비교적 일치된 결과가 나타난 것으로 확인되었으며 이에 따른 원형으로 환산된 소류력 결과를 기존 연구결과인 호안의 허용소류력과 비교함으로써 블록의 수리학적 안정성을 제시하였다. In this Research, in order to improve problems of not enough technical validation and structural and hydraulic stability evaluation when nature-friendly revetment block is applied to field, hydraulic stability evaluation according to hydraulic behavior change of porosity soil block for vegetation reinforcement that secures ecological function was reviewed. By selecting object section, numerical analysis and hydraulic model experiments were performed; for numerical analysis, by using 1-dimensional numerical analysis model HEC-RAS and 2-dimensional numerical analysis RMA-2, one-dimensional(1D) and two-dimensional(2D) numerical analysis were performed; by applying Froude's similarity law, reduced-scale hydraulic model experiments according to vegetation existence were performed. In hydraulic model experiment, for validity of experiment result, the result of velocity and tractive force of reduced-scale hydraulic model experiments was converted to prototype so that it can be compared and reviewed under the same condition of one-dimensional(1D) and two-dimensional(2D) numerical analysis result; as a result, it was confirmed that comparatively united result appeared, and by comparing prototype-converted tractive force result with revetment's allowable tractive force coming from an existing research, block's hydraulic stability was suggested.

現場発生表土を用いた緑化型護岸ブロックの形状と緑化性能の評価

現場発生表土を用いた緑化型護岸ブロックの形状と緑化性能の評価

WAVE RUN-UP OBSERVATIONS ON REVETMENTS WITH DIFFERENT POROSITIES

Wave run-up plays an important role in the design of coastal protection structures. However, none of the existing formulae for wave run-up predictions explicitly considers the effect of revetment porosity. Recently, two revetments have been tested in the Large Wave Flume (GWK) of Forschungszentrum Kuste (FZK), a new type of highly porous polyurethane bonded (PBA revetment) revetment and a smooth interlocked pattern placed concrete block revetment (IPPB revetment), which is considered as "weakly permeable† for the present study. Wave run-up is evaluated by video data analysis based on timestack image processing. The results derived from the timestacks are compared to run-up data measured with conventional wire gauges and the good agreement demonstrates the accuracy and reliability of the video data analysis. The effect of the porosity of the revetment is incorporated into the EuroTop wave run-up formula, showing that for the present case it may reduce the relative run-up heights Ru,2%/Hm0 by about 25 % to 50 % as compared to a smooth impermeable slope.

BONDED POROUS REVETMENTS – EFFECT OF POROSITY ON WAVE-INDUCED LOADS AND HYDRAULIC PERFORMANCE

The porosity and roughness of bonded revetments are both crucial for the hydraulic performance and the wave loading of the revetment and its foundation, and thus for the stability and durability of the entire structure. This is briefly shown by the selected results of a tentative comparative analysis of two large-scale test series performed in the Large Wave Flume (GWK) Hanover with two significantly different revetments: a highly porous and rough polyurethane bonded aggregate (PBA) revetment and an almost impermeable and relatively smooth interlocked pattern placed block (IPPB) revetment. These results motivated the initiation of the three years research project BoPoRe (Bonded Porous Revetments) which has the primary objective to investigate more systematically and separately the relative importance of both porosity and roughness for different slope steepnesses. This project is briefly introduced and the first results of preliminary scale model tests using 9 configurations for the porosity and roughness of the revetment subject to a wide range of wave conditions (surf similarity parameters 0.93-7.21) are briefly discussed.

RESILIENCE OF DIKES AFTER INITIAL DAMAGE BY WAVE ATTACK

The resilience of a dike is quantified in this research as the residual strength, which is the time between initial damage to a dike and dike breach. Unique experiments have been carried out in the Delta Flume of Deltares with a 8.5 m high dike with a clay liner and sand core. Below the still water level the dike was protected with a concrete block revetment and above the water level there was grass on the clay. The tests were carried out with large waves: Hs = 1.6 m. A formula to quantify the erosion of the clay layer as a function of time is derived by combining present and previous experimental results. A formula to quantify the erosion rate of the sand core is derived by combining the present experimental results with existing dune erosion models. The derived formulas make it possible to calculate the probability of failure of the typical Dutch coastal dike with wave attack. This is an important step in the understanding of dike safety.

The Linhuaigang Main Dam Openings Vertical Interlocking Block Revetment Design and Calculation

The design “non-rope opening vertical interlock block” is used in the main dam of Linhuaigang Project for the first time in China. The opening of the block can effectively reduce the uplift pressure induced by waves. The vertical interlock can make block interlock three- dimensionally so as to enhance the integrity of the block and improve the anti-wave performance. The design can not only improve the protection of the main dam slope under long blowing distance and high wind and waves, but also save the use of stone and construction investment as well as protect the environment. Openings vertical interlock concrete block between the rigid in-situ concrete slope and the flexible dry stone slope, not only avoid the shortcomings of in-situ concrete slope suited to soft ground deformation, but also resist the larger storms owing to the better integrity than dry stone pitching ,from the interlocked effect between the blocks. Compared with the entity block, opening vertical interlock block thickness is reduced greatly. The earth dam project of Lin Huai Gang flood control project applied openings vertical interlock block successfully in water conservancy projects .The project has the pioneering position in the use in the wave elements of reservoirs, lakes and the other large water conservancy revetment constructions.

Stability Experiment of Revetment Blocks for Regulation Project of Mulan Creek River

The anti-scour velocity of revetment blocks for flood control project of Mulan Creek river was studied through flume experiments. The results show that the revetment stability is related to the surface smoothness of revetment blocks. If they are paved smoothly, the incipient velocity of the blocks is greater than 4.0m/s, otherwise it is smaller than 3.2m/s. Hence, the smooth armour layer of revetment blocks are more stable than the others. According to distributions of flow velocities during flood in the river, the armor block types for different reaches of Mulan Creek river are suggested.

Analysis on cooling effect of new hollow concrete brick revetment under gravel pavement in permafrost regions

Abstract As a proactive cooling measure for permafrost roadbed, the hollow concrete brick revetment is a new engineering measure to control radiation and convection. The hollow brick revetment engineering test is conducted, which reveals not only the process of its cooling mechanism, but also its cooling performance. The research results suggest that 1) this new structure presents outstanding cooling performance compared with the general embankment, and the annual average temperature of sunny slope drops by about 3 °C and the shady slope by about 1.74 °C. 2) This new structure could effectively eliminate the impact of sunny–shady effect. To be specific, in general embankment sunny slopes are positive in temperature and shady slopes are negative, but the new revetment allows both sunny and shady slopes to have negative temperatures, and thus the temperature difference between sunny slope and shady slope is decreased from 2.22 °C to 0.96 °C. 3) The ground temperature would decrease further as the roadbed heat transfer is in a state of natural thermal equilibrium with the presence of the hollow block revetment. 4) The ground temperature field of the roadbed is stable and symmetrical, the permafrost table is effectively raised, and the temperature in the middle of embankment decreases by 1 °C within a year, so it can be inferred that the temperature drop in embankment is beneficial to its thermal stability in the long run, as proven by the results of the numerical simulation.

Research on Stability Analysis of the Hinge Joint Concrete Block Slope under Seepage Function

The actual project—the Bird Island Park in Shenyang, an example of hinge joint concrete block revetment ,using the FLAC analysis software, and the finite difference method percolation theory to calculate the 29 slope angle the role of a 45kg block under the action of the seepage stability of the slope. Variation in water head discussed in further detail and the role of the different blocks on the slope stability of the quality of the impact of the slope to provide a reference design and application.

Research on Stability Analysis of the Hinge Joint Concrete Block Slope under Seepage Function

The actual project—the Bird Island Park in Shenyang, an example of hinge joint concrete block revetment ,using the FLAC analysis software, and the finite difference method percolation theory to calculate the 29 slope angle the role of a 45kg block under the action of the seepage stability of the slope. Variation in water head discussed in further detail and the role of the different blocks on the slope stability of the quality of the impact of the slope to provide a reference design and application.

Study on Strength Reduction Method Based on Hinge Joint Concrete Block Slope Stability

Slope protection is to ensure the safety of River embankment important infrastructure projects.the actual project--the Bird Island Park in Shenyang, an example of hinge joint concrete block revetment,Using the FLAC analysis software, and the finite difference method percolation theory to calculate the 29° slope angle the role of a 45kg block under the action of Slope stability safety factor,Further discussed in detail the different blocks of different slope and slope stability on the role of the quality factor of safety effects, and draw the best slope and block quality portfolio, which is the slope of reference designs and applications.

Study on Seepage under the Hinge Joint Stability of Concrete Block Slope

Slope is the wide range of large in channel works to ensure the safety of critical infrastructure.The actual project—the Bird Island Park in Shenyang, an example of hinge joint concrete block revetment ,using the FLAC analysis software, and the finite difference method percolation theory to calculate the 29 slope angle the role of a 45kg block under the action of the seepage stability of the slope. Variation in water level discussed in further detail and the role of the different blocks on the slope stability of the quality of the impact of the slope to provide a reference design and application.

Study on Mechanical Properties of New Type Chain Concrete Blocks with Ecological Function

A drainage experiment on chain concrete blocks with ecological function has carried out to study their mechanical properties. This paper presents the stress condition, stability and the effect of infilling gravels, and analyzes the anti-scour capability of the chain concrete block revetment, finally provides some usage suggestions. The results indicate that: The stability and anti-scour capability are good after the blocks are filled with gravels. The infilling gravels are scoured and a certain slope is formed. It is suggested to consider the residual volume of the gravels to save investments. The average thickness of the cushion is suggested to be 15cm to keep the dry stones smooth. The new type chain concrete blocks have such advantages as high anti-shear stress and stability, well permeability, ecological protection, easy construction and low cost.

Evaluation of Environmental and Hydraulic Performance of Bio-Composite Revetment Blocks

It is necessary to develop a concrete revetment block which can cater for environment and at the same time it will be effective in protecting river banks (stabilize the slope of banks) from scouring during flood. In the present study, the environmental and hydraulic performance of the proposed revetment block was evaluated through laboratory and field tests. The tested revetment block is called bio-composite because it is composed of concrete, plastic mesh and biological material (coconut husk). The dimensions of the bio-composite revetment block are 400 mm x 400 mm x 100 mm (length x width x thickness) and has a central opening with a dimensions of 280 mm x 140 mm that has a 10 mm layer of coconut husks protected by two layers of plastic mesh. The coconut husk was selected based on laboratory experiments. The experiments showed that the coconut husk is a good media for grass growth and it allows faster growth of grass compared with other tested types of biological wastes (sugar cane husk and oil palm husk). Field tests were conducted on a selected stream which is located at the Universiti Putra Malaysia, Selangor, Malaysia. The stream banks were protected from scouring by using the bio-composite blocks and monitoring after installation revealed that rate of grass growth was 15% per week. However, it was found that the rate of grass growth is depends on the slope of stream banks. This confirms that the proposed bio-composite block is friendly to the environment and can give a good aesthetic appearance. For a given water depth, hydraulic tests showed that the value of Manning coefficient of roughness for the bio-composite revetment blocks depends mainly on the rate of grass growth. The values of Manning coefficient roughness for the stream were found to range from 0.031 to 0.055.

FLOW-INDUCED FORCES ACTING ON A REVETMENT BLOCK WITH LARGE HEIGHT RELATIVE TO WATERDEPTH OF OPEN-CHANNEL FLOWS

The forces acting on a revetment block used for an element of roughness of the bed in open channel flows were measured by using a three components load cell. The ratio Hp/ ha of the water depth above the blokes Hp to the height of the revetment block ha was 2.1. Turbulent structures of the flow above the revetment blokes were also measured by using a Laser Doppler anemometer (LDA). The friction velocities near the boundary between the top part of blocks and flow were evaluated from the Reynolds stress measured by LDA . These values are nearly equal to the values evaluated from the energy gradient of flow, but less than the values estimated from the drag forces acting on a revetment block. The ratio ks/kc of the equivalent roughness ks for the block to the characteristic height kc of the block is about 1.6.

Soil Retaining Structures: Development of Models for Structural Analysis

The topic of this thesis is the development of models for the structural analysis of soil retaining structures. The soil retaining structures being looked at are; block revetments, flexible retaining walls and bored tunnels in soft soil. Within this context typical structural behavior of these structures is discussed too. The emphasis within the context of model development is on the use of Finite Element analysis as a generic toolbox for model development. In chapter 3 a methodology for the development of models is formulated. Both verification, the testing of the integrity of a model and the relation with models of lower hierarchy, and evaluation, testing the accuracy of a model are important. Accuracy and uncertainty are related aspects of model development. In chapter 4 an analytical toolbox for the development of models for structural analysis is given. One of the observations in the formulation of this chapter was that groundwater flow can be evaluated based on the same principle as equilibrium of stresses; the principle of virtual work. In the next three chapters 5, 6, and 7 three examples are given of development of models for the structural analysis of soil retaining structures. In chapter 5, a model for the stability against sliding of the top-layer of a revetment is put forward. The model is evaluated against prototype information. The validity to use Delta flume measurements to validate models for the design of a revetments cover-layer is being reconsidered, as there is reason to believe that the undrained response which is attributing to'the strength of a cover-layer has 3 dimensional effects being overlooked in a 2D measurement. In chapter 6, the models for sheet-pile retaining walls are described. The development of finite element analysis for sheet pile walls is described. Subsequently some of the verification analyses are described including an analytical solution derived from plasticity theory. Finally the finite element model is validated against prototype measurements, i.e. the Karlsruhe sheet pile test (1993). Within this context the test is evaluated applying inverse analysis. One of the conclusions was that a distinct difference between the in-situ stiffness of a sand layer and the stiffness as derived from a laboratory test was found. The reason for this is thought to be the breaking up of structure during sampling in advance of the laboratory testing. This structure is not recovered during preparation in the laboratory. The model evaluation indicates that the application of Finite Element analysis improves the accuracy in comparison to the empirical models. In chapter 7, the structural models for the design of a tunnel liner are discussed. The problems related to bored tunnelling in soft soil are discussed. The model hierarchy for the evaluation of the tunnel liner is discussed. In the second part of this chapter, a back-analysis of the measurements from the Second Heinenoord tunnel, with a finite element model is described. From this it comes forward that the uncertainty with respect to tunnel liner design is mainly related to the construction phase, i.e. tunnel ring assembly. In comparison to sheet pile walls, the soil loading of tunnel liners are easier to model.

ARTICULATED CONCRETE BLOCK STABILITY TESTING1

ABSTRACT: An articulated concrete block revetment system was developed by the U.S. Army Corps of Engineers to test and evaluate the practicability of the protocols for overtopping and channelized flow conditions. Test facilities were constructed, prototype articulated concrete blocks were fabricated and installed into the facilities, and the blocks were tested using the established protocols. The test results indicated that both the overtopping and channel flow tests yielded similar results: the blocks reached a point of instability at approximately the same velocity and shear stresses. The similar test results indicate that only one protocol is required to evaluate an articulated concrete block system. It was demonstrated that both protocols can be effectively conducted. It is recommended that the overtopping test be adapted as a standard test procedure because of its reduced construction costs and its efficiency compared to the channelized test.

ブロックマット工法を用いた多自然型川づくりの施工例

In recent years, river revetment improvement work designed to create river works for natural conservation has been implemented in various parts of the country, in response to growing public consciousness of environmental conservation and to the revision of the River Law. The block mat system, which can be used to restore a site's vegetation by creating an earth cover, is a suitable method for constructing revetments on quasi-natural rivers. The “Basic Guidelines for Disaster Restoration to Conserve Beautiful Mountains and Rivers” designates it as a quasi-natural river revetment restoration method that can be applied to rivers with a flow velocity of up to 4m/sec. When it is actually applied, the method should be studied based on verification of the flow stability of the revetment blocks. This report presents an example of its application to river works for natural conservation performed after verifying the flow stability using a “sliding-colony” model and a “peeling” model.