Earth Anchor Research Articles

Field Pull-Out Tests of Percussion Driven Earth Anchors (PDEAs)

Percussion driven earth anchors (PDEAs) are driven into soils using an installation steel hammer rod. PDEAs are relatively easy to install and have gained wide applications recently. The Texas Department of Transportation (TxDOT) planned to use these anchors for slope stability mitigation along the Clear Fork Trinity River at Interstate Highway 20 (IH-20) in Benbrook, Texas. However, there are no straightforward design and construction guidelines for these systems. In addition, the pull-out capacity and failure mechanisms of PDEAs in clayey soils have not been thoroughly studied. In this study, three PDEAs, Duckbill model 138 II (DB-138 II), were installed and tested on the proposed west channel bank slope to acquire the ultimate pull-out capacity. The anchors were embedded to an average depth of 10 feet into the slope bank, predominantly consisting of sandy lean clay (CL) soil. The slope was graded at an average 2:1 to 2.5:1 configuration. After installation, the anchors were subjected to an upward pull-out force using a hydraulic jack system to measure their pull-out capacity. The pull-out load, displacement, and strains were continuously recorded with a load cell, a linear variable differential transformer (LVDT), and a strain gauge, respectively. Pull-out load versus displacement curves were produced and analyzed to determine the behavior of the anchors. An empirical estimation method was then chosen to estimate pull-out capacity based on undrained shear strengths obtained either from laboratory tests or in situ Texas cone penetration (TCP) data. The comparison between estimated and field-obtained pull-out capacities showed that the pull capacity estimated using TCP data resulted in reasonably good agreement with the field-obtained capacity. The field experiment results help us to understand the relationship between the calculated and actual field pull-out resistance when PDEAs are used in clayey soil slopes.

Residual tensile force estimation method for earth anchor using elasto-magnetic sensing system.

The earth anchor method is used to prevent landslides, and repair and reinforce cut or steep slopes due to its benefits of ease of construction and economic feasibility. However, the loss of anchor force has become a problem, which may cause failure and collapse of slopes when the anchor force drops below the design anchor force. While numerous studies have been conducted to solve this problem, measuring the residual tensile force of existing earth anchors remains a challenge, as prior studies required sensors to be installed inside structural members at the time of construction. Therefore, to address this limitation, an experiment was performed in this study to develop an elasto-magnetic (EM) sensor for measuring tensile force based on the EM effect, which could be installed on externally exposed anchor heads. The commercial software ANSYS Maxwell was used to analyze the optimal sensor design for the experiment. Additionally, a series of tests to measure the tensile force was conducted by fabricating the sensor based on the numerical analysis results. The area of B-H curves measured by developed EM sensor was increased according to the decrease of tensile force. Also, The tensile force estimation equation was derived and verified using measured data. According to the results, the proposed method can be one of the solution for measuring residual tensile force of earth anchor.

Earth Earth Anchor as a Deep Concrete Concrete Structure

Construction development of territories with complex engineering and geological conditions with the presence of unstable rugged relief is a complex geotechnical problem. Issues related to ensuring the safe production of installation work for the construction of any object in such territories relate to a multifactorial problem associated, first of all, with the development of special geotechnical technologies tied to real geotechnical conditions of the relief, loads from existing buildings and structures and, secondly, real their implementation at a specific construction site. Modern geotechnical construction has in its arsenal methods and technologies for solving these complex problems. The use of advanced computer programs such as GeoWall, GeoStab, Plaxis, etc. allows the development of geotechnical objects of any complexity. To identify the most appropriate geotechnical technology, it should be mandatory to use the interactive design method. This is “a developed project - an experimental site - a real project”. Moreover, this type of design should be multivariate using various geotechnical technologies and geotechnical structures. The feasibility study of all elements in interactive design is of no small importance. Any element in the design must be economically feasible and technically feasible. The considered case from the geotechnical practice of the construction of the object confirms the fact that thanks to the availability of modern design and production tools, it is possible to solve any complex problems.

Analysis of Slope Stability

Abstract In the paper the numerical modelling of ensuring slope stability and their analysing with using of different numerical methods are presented. We have designed the cutting walls with earth nails and anchors securing for modelling of slope stability ensuring. The calculate and the mechanism of failure process of the reinforced slopes were studied using the different methods for slope stability. The nailing significantly increased the stability level for using Spencer method. The anchors increased the stability level for using Spencer method. Increasing the nail or anchors length improved the stability of the reinforced slopes. The reinforced slope exhibited a significant the stability level.

Outlook and Special Properties of Earth Anchors and Screw Piles in Burial of Modular Protection Dikes in Nonrocky Ground

Securing of temporary hydrotechnical structures (water-filled, panel-mounted, and other types of dikes) of different heights by means of flat earth anchors and screw piles designed to protect population centers and infrastructure against large-scale floods is considered.

ANALYSIS OF REMEDIAL ACTIONS DESIGNED TO STABILIZE A HIGHWAY CUT IN A LANDSLIDE AREA

The Carpathian flysch is widely recognized as a geological environment prone to slope movements. This fragility in such an environment is due to its complicated geological and hydrogeological conditions. Weakened slip surfaces (developed in clay like material), in combination with present or past tectonic activity and difficult hydrogeological conditions with aquifers under pressure, are the main causes of slope movements. The article proposes to analyze the design of remedial action in a landslide area near Žilina. Slip surfaces and water conditions are assumed regarding present geotechnical monitoring. Deep cut with two rows of pile walls is analyzed by the limit equilibrium method and finite element analysis. Interaction between two walls and the effect of an amount of volume of sliding mass on resultant earth pressures and anchor forces were studied. The results from finite element analysis are compared with analytical calculations and the differences are discussed.

Numerical simulation and parametric analysis of multi-anchor walls using the finite element method

Abstract The paper describes the first reported attempt to numerically simulate the performance of full-scale steel multi-anchor reinforced soil walls (MAWs) during construction using a commercially available two-dimensional finite element method (FEM) model. The numerical simulation results are compared to the measurements taken from three 6 m-high MAW structures that were constructed under carefully controlled in-door laboratory conditions. The walls were nominally identical but constructed with three different sandy soils varying with respect to soil stiffness and shear strength. Earth pressures and anchor loads were monitored during construction and in-situ anchor pullout tests were also performed. Numerical predictions are judged to be in reasonable agreement with most physical measurements. A novel technique was the use of in-situ anchor plate pullout test results to back-calculate initial elastic modulus values for the hyperbolic constitutive soil model used in the study. The physical and numerical results are extended by considering a wider range of wall parameters (initial soil stiffness, shear strength, anchor length and wall height) using the same FEM model. The results of this parametric analysis provide further insight into the influence of the magnitude of different input parameters including wall height on wall performance. The main objective of this study was to generate a satisfactory definition of end-of-construction conditions. The paper also reports the results of a series of case studies that can be used by design engineers to benchmark-test FEM models proposed for MAW projects that are too complicated for analysis and design using conventional simple strength-based internal stability methods and where performance-based design requires estimates of wall deformations.

Hydraulic Circulation Test and CFD Analysis of Prestressed Cementing Unit Earth Anchor

In the process of thickened oil thermal recovery, the pre-stress cementing needs to be anchored at the bottom of the casing pipe. And the reliable opening and closing of anchor flukes directly influence the anchoring. In allusion to the problems of how to get the critical value of drilling fluid flow rate of when the anchor flukes begin to open, completely open, begin to close and completely close, whether different nozzles can open or close reliably, getting the corresponding differential pressure and discharge coefficient of the different nozzles, this paper conducts a study from both theory and experiment to obtain the relevant parameters. By simulating the anchor in actual work and dealing with the data, we conclude that: (1) The fluke can open smoothly when the flow rate reaches a certain flow and it can also close smoothly when the flow rate declines. (2) The critical flow rate of the flukes, when two kinds of anchors are with different nozzles, has been acquired. (3) Corresponding differential pressure and discharge coefficient of the different nozzles in different flow rate have been ascertained.

수치해석기법을 이용한 개착식 지반굴착공사의 영향인자 분석

우리나라 지반공학 기술의 발달로 지반굴착 공사가 대규모로 수행되고 있으나, 지반굴착시 공사현장 또는 인접구조물에 직,간접적인 피해를 유발하는 사고는 여전히 빈번히 발생하고 있다. 특히 주거시설이나 상업시설이 밀집해 있는 도심지의 지하터널, 도시철도 역사, 대규모 상업시설, 초고층 빌딩의 기초 공사 등으로 인한 지반굴착관련 사고가 빈번히 발생하고 있어 경제적인 손실 뿐 아니라 인명피해가 발생하여 사회적인 비용이 급속히 증가하고 있는 실정이다. 본 연구에서는 빈번히 발생하는 개착식 흙막이 굴착관련 사고를 방지하기 위하여 최근 발생한 개착식 흙막이 굴착공사로 인한 다수의 사고 및 인접시설물에 영향을 끼친 사례를 수집, 분석을 수행하여 사고발생 원인에 대하여 고찰하고, 수치해석기법을 사용하여 국내 대표적인 지반조건(내륙, 해안특성) 및 공사공법에 따른 굴착시 영향 분석을 수행하였다. 25건의 사고사례를 분석한 결과, 주요 영향요인으로 지반조사의 부실, 가시설 구조체의 불안정 및 지하수의 처리 미흡 등으로 나타났으며, 이 외 여러 요인들이 복합적으로 작용하여 굴착현장에 문제를 발생시키는 것으로 나타났다. 국내의 대표적인 지반조건 및 시공경향을 고려한 22개의 case에 대한 수치해석결과는 일반적인 내륙지역에서는 차수공법에 비해 배수공법에서 침하가 크게 발생하고, 연약지반 및 암반의 불연속면이 발달한 지역에서는 earth anchor 공법 적용시 면밀한 검토가 필요하며, 압밀이 진행 중인 점토지반에서는 과잉간극수압에 대한 고려가 반드시 필요한 것으로 나타났다. In this study, an analysis about the causes of different types of excavation on accidents is required in order to prevent the frequently occurring accidents related to the earth retaining structure and excavation. Also, analysis of influence was performed by using numerical typical soil conditions and construction trend using numerical analysis method. According to the analysis results of 25 accident cases, the main influence factors were found as following: insufficient of soil survey, instability of temporary facility and lack of groundwater treatment, etc. Furthermore, in the numerical analysis result of 22 cases, drainage method was occurred larger settlement than waterproof method in the Inland. In case of applying the earth anchor method, it needs more detailed in the regions, which are discovered soft ground or rock discontinuities. Also, The consolidated clay absolutely needs further consideration of excess hydrostatic pressure.

Model Tests on Force Characteristics of Reinforced Retaining Wall

The recent research and development of the reinforced retaining wall is composed of cantilevered reinforced concrete retaining walls which symmetric set on both sides of subgrade and through roadbed width of counter-pulled anchors. The prestressing force can be applied on anchors.The retaining wall has the advantange of high safety, lateral small deformation , wide applicable range and low requirements for the foundation bearing capacity. But due to the lateral restraint of bolt, the soil pressure distributions of retaining wall change a lot. The change will have a significant impact on structures. In order to reveal the reinforced soil retaining wall pressure distributions, laboratory model test was done. The monitoring instruments such as earth pressure cells, anchor rope dynamometers and dial indicators were installed. Research and analysis on the loading process reinforced type soil retaining wall under soil pressure, the lateral earth pressure and anchor rope tension change rule were researched and analysed. The experimental results showed that with the increasing of filling soil height, the retaining wall had a tendency to tilt outward. The basolateral external pressure is larger than the inside pressure. At the same time, anchor tension increased as the top loading increased. Lateral earth pressure distribution is parabolic. Soil pressure around the anchor is larger than other area, the soil arch effect is significant.

점토 지반에서 인발속도에 따른 판앵커의 극한 인발저항력 분석

Anchors are primarily designed and constructed to resist outwardly directed loads imposed on the foundation of a structure. These outwardly directed loads are transmitted to the soil at a greater depth by the anchors. Buried anchors have been used for thousands of years to stabilize structures. Various types of earth anchors are now used for the uplift resistance of transmission towers, utility poles, submerged pipelines, and tunnels. Anchors are also used for the tieback resistance of earth-retaining structures, waterfront structures, at bends in pressure pipelines, and when it is necessary to control thermal stress. In this research, we analyzed the uplift behavior of plate anchors in clay using a laboratory experiment to estimate the uplift behavior of plate anchors under various conditions. To achieve the research purpose, the uplift resistance and displacement characteristics of plate anchors caused by the embedment ratio, plate diameter, and loading rate were studied, compared, and analyzed for various cases.

Design and Simulation of New Unit Earth Anchor for Pre-Stressed Cementing

During prestressed cementing for heavy oil thermal recovery wells, it is encountered that the earth anchor connecting to the bottom of the casing string anchors difficultly, and anchoring force can not meet design requirement. A new type of unit and resettable earth anchor structure for prestressed cementing is introduced. The project can use multiple unit combination according to different formation condition and can choose different length of the earth anchor fluke according to diameter of the well. ANSYS/LS-DYNA is used to simulate the process of the fluke digging into the wall of the borehole with different diameter. Variation of reaction force of rock upon the fluke with different initial digging angle is analyzed, and the most favorable angle range in which the fluke digs into the borehole wall is concluded. A favorable reference to determining fluke's geometric parameter and selecting type of the claw is provided.

사질토 지반에 설치된 판앵커의 인발속도에 따른 저항력 분석

Anchors are primarily designed and constructed to resist outwardly directed loads imposed on the foundation of a structure. These outwardly directed loads are transmitted to the soil at a greater depth by the anchors. Buried anchors have been used for thousands of years to stabilize structures. Nowadays, various types of earth anchors are used for the uplift resistance of transmission towers, utility poles, submerged pipelines, and tunnels. Anchors are also used for the tieback resistance of earth-retaining structures, waterfront structures, at bends in pressure pipelines, and when it is necessary to control thermal stress. In this research we analyzed the uplift behavior of plate anchors in sand using a laboratory experiment to estimate the uplift behavior of plate anchors under various conditions. To achieve the research purpose, the uplift resistance and displacement characteristics of plate anchors caused by the embedment ratio, plate diameter, and loading rate were studied, compared, and analyzed in various cases.

Lateral Earth Pressure Coefficients for Anchored Sheet Pile Walls

AbstractConventional methods used for the design of anchored sheet pile walls are based on the lateral force and moment equilibrium of active and passive earth pressures and anchor force. Although it has been known for decades that the stress concentration occurs around the anchor level because of the restricted wall movements, this stress concentration is not considered in determining the lateral earth pressures. A parametric study using conventional and numerical methods was performed to investigate the behavior of single-level anchored sheet pile walls, and the lateral earth pressures, wall bending moments, and anchor forces were analyzed. The study results indicate that the conventional methods for the conditions considered and cases studied overestimate the wall bending moments, whereas the anchor forces are underestimated. New lateral earth pressure coefficients that consider the stress concentration around the anchor level were developed and proposed to be used in the design of single-level anchore...

세미 오픈컷 역타공법의 현장적용에 관한 연구

지하공사는 상부층의 구조물과 연계된 시공순서에 따라 Bottom-Up공법, Up-Up공법 그리고 Top-Down 공법으로 대별할 수 있다. 탑다운 공법을 사용하면 건물의 본구조를 흙막이지보공으로 이용하면서 상층에서 하층으로 굴착과 구체구축을 반복하여 시공함으로써 인접구조물이나 주변 지반의 변위를 극소화 시킬 수 있다. 이는 토류벽의 안정성이 높으며, 각층의 바닥슬래브를 작업공간으로 사용하여 도심지 공사에서 작업장 확보가 용이하다. 그러나 굴토작업이 슬래브 하부에서 진행되므로 작업 능률 및 작업환경이 저하되고, 어스앵커 공법보다 경제성이 없다는 이유로 다소 회피하는 경우가 종종있다. 따라서 본 논문에서는 터파기 공사는 세미오픈컷 공법을 적용하고 흙막이 공법에는 지하연속벽(슬러리월)을 그리고 지보공으로는 C.W.S공법을 적용한 역타공법으로 대상현장을 중심으로 기존 역타공법과 경제성, 공사기간 및 작업성 등을 분석 제시하였다. 토사운반 및 철골설치공사 작업의 용이성과 PRD 공사의 정밀도 향상 등의 품질관리가 우수하며, 공기단축이 가능하였다. Construction methods for underground structure are classified as bottom-up, up-up, and top-down methods depending on the procedure of construction related to a superstructure. In top-down construction methods, building's main structure is built from the ground level downwards by sequentially alternating ground excavation and structure construction. In the mean time, the main structure is also used as supporting structure for earth-retaining wall, which results in the increased stability of the earth-retaining wall due to the minimized deformation in adjacent structures and surrounding grounds. In addition, the method makes it easy to secure a field for construction work in the downtown area by using each floor slabs as working spaces. However top-down construction method is often avoided since an excavation under the slab has low efficiency and difficult environment for work, and high cost compared with earth anchor method. This paper proposes a combined construction method where semi-open cut is selected as excavation work, slurry as earth -retaining wall and CWS as top-down construction method. In the case study targeted for an actual construction project, the proposed method is compared with existing top-down construction method in terms of economic feasibility, construction period and work efficiency. The proposed construction method results in increased work efficiency in the transportation of earth and sand, and steel frame erection, better quality management in PHD construction, and reduced construction period.

The Overall Shift Device of the Derrick and the Finite Element Calculation

An overall shifting device was designed to move the drill as a whole, avoid the repeated assembly and disassembly of the cluster wells drill. The hydraulic system of the device and the strength of the loaded parts of the system was checked; The earth anchor, the size of the earth anchor was determined and ANSYS analysis were conducted to ensure its supporting function.

Seismic retrofit of plain concrete piers of railroad bridges using composite of FRP-steel plates

This study is planed to solve the overturning problem and manifestation of tensile cracking of plain concrete piers of railroad bridges. For the overturning problem, earth anchors are used to fix the bottom of a pier to a rock-foundation using prestressing cables. Composite of Fiber Reinforced Polymer (FRP) and steel plates (FSP) are attached longitudinally on the surface of the pier to prevent cracking. Then, FRP band strips are wrapped onto the composite of FRP and steel plate to provide lateral confinement. Push-over tests in field show that the earth anchors are effective in preventing the overturning of the pier, and that the FSPs and the FRP strips prevent the cracking of concrete and increase the strength in bending.

Influence of Transient Flooding on Multi-Anchor Walls

The paper presents the results of three full-scale tests that were carried out to investigate the influence of transient flooding on the performance of multi-anchor reinforced soil walls (MAW). The walls were constructed to a height of 6 m and flooded from the front of the structures to about mid-height and then drained in two to four stages. The walls were constructed with three different sand soils varying with respect to permeability, fines content and shear strength. Earth pressures and anchor loads were monitored during the flooding and draining stages and in-situ anchor pullout tests were performed. The analysis of results showed that the wall facings were very permeable and thus prevented unbalanced hydrostatic or seepage forces from developing during drawdown that could increase anchor loads beyond drained condition values. The accuracy of the current PWRC (2002) analytical model to estimate anchor capacity of MAW systems was demonstrated to vary widely depending on soil type and whether the soil was flooded or drained. However, on the load side, the method proposed by Miyata et al. (2009) to predict anchor loads was judged to be more accurate than the current BS8006 (2005) and PWRC (2002) methods based on the mean and spread of bias statistics where bias is defined as the ratio of measured to predicted anchor load.

Large Woody Debris Structures for Sand-Bed Channels

Described is a method for channel erosion control and habitat rehabilitation featuring intermittent placement of structures made of large woody debris. This method is expressly tailored to address severe problems typical of incised channels with little sediment coarser than sand. In these types of environments, buoyancy forces are typically more important factors in woody debris stability than fluid drag. Buoyant forces are counteracted by the weight of the structure, earth anchors, and sediment deposits. Design concepts were tested in a demonstration project constructed along 2 km of channel draining a 37-km² watershed. Large woody debris structures reduced velocities in the region adjacent to the bank toe and induced sediment deposition and retention. Construction costs per unit channel length were 23–58% of costs for recent stone bank stabilization projects within the same region. During the second year following construction, 31% of the structures failed during high flows, probably due to inadequate anchoring.

Earth Anchor Design (1)

Earth Anchor Design (1)