Prestressed Anchor Cable Research Articles

Reinforcement Mechanism and Optimisation of Reinforcement Approach of a High and Steep Slope Using Prestressed Anchor Cables

Using prestressed anchor cables is one of the most common approaches for reinforcing slopes. By establishing a calculation model for a high and steep slope, the changes of displacement of slope foot and increment of force on the cables under different prestresses were calculated. Furthermore, the influence of prestress on the changes of displacement of slope foot and force on the cables was analysed. By analysing the changes in force on cables in different parts of the slope, the reinforcement mechanism of a prestressed anchor cable on the slope was attained. The result showed that the reinforcement effect of prestressed anchor cable on the slope was mainly attributed to it effectively restricting the displacement of sliding mass in the slope, while the effect of cables in the lower part of the slope was more significant than that of those in the upper part of the slope. Therefore, to reduce the number of cables, decrease the construction difficulty of cables and save money, it is feasible to remove cables in the range of the upper-third of the slope. Afterwards, by improving the cable prestress in the range of the lower-third and reducing the cable prestress in the middle, the safety factor of the slope can satisfy design requirements, thus reinforcing the slope.

Stability analysis of slopes reinforced with anchor cables and optimal design of anchor cable parameters

Pre-stressed anchor cables are widely used in slope engineering for effectively improving slope stability as a reinforcement measure. Based on assumptions of stresses on a slip surface, this work proposes a new limit equilibrium (LE) method to analyse the stability of slopes reinforced with anchor cables. Meanwhile, the nonlinear Mohr–Coulomb (M–C) strength criterion has been adopted to describe the slope sliding for shear failure of the slip surface. Then, after comparison and analysis of several examples, the feasibility of the proposed method is verified. Compared with the traditional LE methods, the proposed method has a simple calculation process without iterative loop calculation of the slope factor of safety, and a reasonable solution can also be obtained. Furthermore, the slope reinforced by anchor cables with more than a row can be simplified into a slope with a row to analyse its stability because the same stability would be obtained for the reinforced slope with different reinforcement patterns under an equivalent reinforcement relation. Thereafter, to facilitate the engineering application and optimize the design of anchor cable parameters, the stability charts of the reinforced slope under the linear M–C strength criterion are drawn.

3D Finite Element Analysis of Ocean Strengthened Side Prestressed Pier by ANSYS

ABSTRACT Sun, L.; Xie, W., and Tang, K., 2018. 3D finite element analysis of ocean strengthened side prestressed pier by ANSYS. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 499–506. Coconut Creek (Florida), ISSN 0749-0208. In this study, the ocean strengthened prestressed anchor cable of flood diversion sluice pier of Shu River Hydropower Station Project is modeled by the international general finite element program——ANSYS. After the anchor cable pretension force applied at the point, various load combination and conditions combination reasonably considered, the finite element analysis is performed and the effect of the prepress is determined, then the results of the stress and strain characteristics of the structure under static loadings are analyzed, more deeply on reinforcement conditions. Through these statistics, characteristics of prestressed pier three-dimensional finite element analysis are summarized mo...

MECHANICAL PERFORMANCE OF COMPOSITE RETAINING AND PROTECTION STRUCTURE FOR SUPER LARGE AND DEEP FOUNDATION EXCAVATIONS

The reliable retaining methods and a good stress system are the key to the success of super large and deep excavation engineering. In this paper, the deepest foundation pit in Hainan province is taken as an example. The method of mutual verification between in-situ monitoring and numerical simulation is adopted. The mechanical performance of composite retaining structure composed of reinforced concrete cast-in-situ soldier pile wall, diaphragm wall and prestressed anchor cable are studied. The interaction between the reinforced concrete cast-in-situ pile retaining structure at the upper part and the diaphragm wall retaining structure at the lower part is revealed, and the variation of internal forces of the diaphragm wall retaining structure in the time and space is demonstrated. And then the influence of insertion ratio and rigidity on the mechanical properties of diaphragm wall is discussed. Research shows, the range of interaction between the upper and lower retaining structures is limited. During the excavation process, the maximum bending moment of the diaphragm wall is always near the excavation surface, and the curvature of the bending moment curve decreases gradually with the increase of excavation depth and axial tension of anchor. When the insertion ratio of diaphragm wall increases, the maximum bending moment moves upward. With the rigidity of the diaphragm wall increases moderately, the bending moment of the retaining structure increases, but the lateral displacement decreases. The research results can provide theoretical basis and practical experience for the composite retaining structure design of super large and deep foundation excavations.

Stability Analysis and Reinforcement Treatment of Open Pit Slope

The construction of mine surface facilities shall be carried out according to the scope of mining rights and ease of use. The underground mining of Shirengou Iron Mine uses filling method mining, and the filling station needs to be built on the surface. According to the design, it is constructed near the open pit. Based on the protection of the filling station system, the stability analysis of the open slope is needed. The failure mode of iron ore open slope is circular arc sliding failure mode. The calculation model of the stability analysis is calculated by the residual thrust method. The maximum residual thrust of the I-I section is 128.9 tons/meter, and the maximum residual thrust of the II-II section is 75.39 tons/meter. According to the calculation results, the safety measures such as slope dressing and masonry retaining wall are carried out on the open slope, and the grouting prestressed anchor cable is selected to reinforce the slope. The anchor cables are connected by reinforced concrete frame and beam, and the concrete is used. The beam acts as an anchor pier. In order to effectively consolidate the slope stability, the grouting method is combined to effectively treat the slope. After a series of slope reinforcement measures, the stability of the open slope and the safety of the filling station can be guaranteed.

Limit analysis under seismic conditions of a slope reinforced with prestressed anchor cables

Based on limit analysis and pseudo-dynamic methods, a proposed method for evaluating slope stability under seismic conditions that considers dynamic changes in the axial force of the anchor cables is presented. The case study shows that compared to the computational conditions that neglect the dynamic changes in axial forces, the dynamic safety factors obtained by the proposed method are greater, whereas the dynamic variation amplitudes of the dynamic safety factors obtained by the proposed method are smaller. The better anti-seismic effect of the anchor cables due to considering the dynamic changes in axial forces is reflected by the proposed method.

Dynamic response of a slope reinforced by double-row anti-sliding 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.

Stability Analysis and Reinforcement of a High‐Steep Rock Slope with Faults: Numerical Analysis and Field Monitoring

This study presents a stability analysis of a high‐steep rock slope with two faults during excavations and evaluates the effectiveness of a proposed reinforcement method using prestressed anchor cables. A 3D finite difference model was established based on the strength reduction method using FLAC3D software. The influence of various fault conditions and the effectiveness of the reinforcement on the slope stability during the excavation process were analyzed and compared to field monitoring data. The numerical analysis and field monitoring results showed that the fault close to the slope surface (f20) was prone to the local instability under external forces caused by the excavation, but a fault further away from the slope surface (f14) had insignificant influence on the stability of the slope. Based on the numerical analysis results, the proposed reinforcement measure can increase the factor of safety (FOS) of the slope by 19.2%. The field monitoring data also showed that the displacement of the monitoring point gradually decreased after the reinforcement, and the deformation of the slope was effectively controlled.

Reinforcement Analysis of Toe Blocks and Anchor Cables at the Xiluodu Super-High Arch Dam

High stress concentrations near an arch dam–foundation interface may cause cracking and failure, particularly in super-high arch dams. Appropriate reinforcement measures are usually needed at the dam toe to increase the shear strength and bearing capacity of the rock mass foundation. In this paper, the criteria and procedure for reinforcement design of dam toe are first given, as priority issues in the overall safety assessment of super-high arch dams. A complete reinforcement analysis method covering the calculation of reinforcement force, effect evaluation and monitoring validation is proposed. With the Xiluodu super-high arch dam as an example, the reinforcement analysis under the numerical simulation and physical model tests performed are described in detail. The results show that the reinforcement measures adopted, such as the toe block and pre-stressed anchor cables, contribute to decrease the local high stresses at the dam toe, as well as increase the cracking initiation factor and the overall safety factor of the dam–foundation system. The reinforcement force loss of anchor cables during the subsequent construction stage has a limited effect on the dam performance. In terms of improving the stability at dam toe, the reinforcement of anchor cables is suggested to be implemented as early as possible. The reinforced dam is finally verified by field monitoring during the operation period. No anomalies in deformation, stress and seepage response near the dam are identified, and the arch dam is shown to perform as desired.

Stability analysis of complex rock slopes reinforced with prestressed anchor cables and anti-shear cavities

To evaluate the stability of reinforced complex rock slopes, an evaluation method for slope stability is proposed in this paper. In the proposed method, the force equilibrium of the potential slide mass is analyzed by treating the traction on the potential failure surface as an external force. The potential sliding direction is assumed to be the opposite direction of the resultant shear force on the potential failure surface, and the factor of safety is defined as the ratio of the available resisting force to the actual mobilized force. Through classic cases, the proposed method successfully predicts the stability of a slope critical to failure, and is compared with the traditional methods. Finally, the proposed method is used for a stability analysis of the left bank slope of the Jinping first stage hydropower station, considering two main reinforcing measures, prestressed anchor cables, and anti-shear cavities. Results indicate that the effects of the anti-shear cavities are more positively significant than the effects of the prestressed anchor cables. The safety factor is remarkably increased by the anti-shear cavities, which validates the importance of anti-shear cavities on slope stability.

Experimental Study on Load-Displacement Relationship of Prestressed Cable in Red Clay Stratum

The P-S curves of prestressed anchor cable are obtained by field pull-out tests in the red-clay stratum in Guiyang area. The P-S curves of different theoretical models are discussed base on the theoretical analysis. The elastic and plastic displacement of prestressed anchor cable are analyzed. The results shows that, the anchoring effect are mainly effected by the red-clay mechanic properties in the red-clay stratum; the P-S curve of anchor bolt can be fitted well by the exponential model and conformed to the actual; the plastic displacement is used to anchor’s damage index are more truthfulness in the red-clay stratum.

基于极限平衡理论和有限元强度折减法的预应力锚索加固边坡稳定性分析研究

本文以贵阳会文变至渔安变220千伏线路铁塔边坡为依托工程，采用极限平衡法和有限元强度折减法对高边坡在预应力锚索加固前后的稳定性进行计算分析，探讨了施加预应力锚索后对边坡位移及稳定性的影响，通过模型计算结果与监测资料的对比得出结论：极限平衡理论与有限元强度折减法得到的安全系数和滑动面基本一致。监测资料与计算结果相吻合，预应力锚索加固后该边坡处于稳定状态，本文研究成果可为类似工程设计提供参考。 The paper uses the Slope of 220 kv Variable Pressure Transmission Iron Tower from Huiwen to Yu’an in Guiyang as an engineering example. It calculates and analyses the high slope stability after reinforcement by prestressed anchor cable based on the theory of limit equilibrium method and finite element strength reduction method. It discusses the influence of prestressed anchor cable on stability and displacement. The calculation results are compared with the collected monitoring data and the conclusions are drawn. The safety factors and sliding surfaces by limit equilibrium method and finite element strength reduction method are almost the same. The monitoring data are consistent with the calculation results, and the slope is stable after reinforcement by prestressed anchor cable. Thus, the result can be used as a reference for engineering design.

The 102 Landslide: human–slope interaction in SE Tibet over a 20-year period

The evolution of large-scale landslides should be studied because, over long periods of time, primary remediation measures may suffer reduced efficiency or have to be adjusted many times. The 102 Landslide in southeast Tibet, which originally formed in 1991 with a volume of 5.1 million m3 and still exhibits post-failure activity, provides a distinctive case study. The landslide evolved from earthquake destruction and unloading, rainfall-triggered sliding, and debris flow to sands sliding slopes. The NE ringed scarp receded by 38.96 m during a five-year period (2003–2008). The total recession was 160 m with a total area of 2500 m2 during a 17-year period (1991–2008). Although several types of remediation measures were applied and were temporarily effective, the normal function of the Sichuan–Tibet Highway was affected by landslide reactivation from time to time. Actual effects of the engineering measures such as retaining walls, prestressed anchor cables, and drainage ditches confirm that hasty governance of this type of large-scale landslide is generally unfeasible over long time periods. Finally, an approach involving a tunnel running backward from the front face has been adopted as a permanent solution to large-scale moraine slope failures: This engineering practice has been in progress since April 2012. This paper describes the evolution of the 102 Landslide, the engineering interventions to mitigate the effects of the landslide on the Sichuan–Tibet Highway, and the choice of tunneling as a final mitigation measure. The present study concludes that approaches that allow escape from developing geo-hazards should always be the initial choice.

Research on double-layer electric isolation protection technology of prestressed anchor cable

Research on double-layer electric isolation protection technology of prestressed anchor cable

Reflection on the application of prestressed anchor cables in slope engineering treatment

Reflection on the application of prestressed anchor cables in slope engineering treatment

Research on Stability Calculation Methods for Grillage Supporting Structure with Pre-Stressed Anchor

Aiming at prestressed anchor cable frame in the presence of reinforcement landslide problem, through the selection of test points, the paper study and tested soil pressure, frame internal force and prestress losses under prestressed anchor cable frame beam, reveal the law of internal force distribution, and provides a theory basis for the rational design of prestressed anchor cable in landslide..

Experimental study on corrosion progress of interior bond section of anchor cables under chloride attack

A corrosive medium (particularly a chloride medium) with water is typically found in the working environment of a prestressed anchor cable. The anchor cable structure itself has certain characteristics such as complex details, high working stress, extremely difficult control in construction, and hidden operation in construction and maintenance. Thus, corrosion is the key problem related to the use of anchor cables. Relevant research focuses on the corrosion type, basic corrosion principle, and corrosion development law of anchor cables at the qualitative level. In this paper, the corrosion progress of the interior bond section of anchor cable under chloride attack is studied through long-term systematic experiments and theoretical analysis. Serial time-varying models, such as those for instantaneous corrosion rate, weight loss rate of corrosion, and tensile capacity, are established based on the Hill function. Two factors, namely, chlorine ion concentration and pore water saturation of the ground around anchor cables, are set as the independent variables in all of the models.

Analysis of the Research Status and Trends of Anti-Slide Pile with Prestressed Anchor Cable

The research status of anti-slide pile with prestressed anchor cable is summarized from the aspects of test, calculation and optimization design. The main problems in the design and application are elaborated, especially the interaction and deformation coordination among prestressed anchor cable, anti-slide pile and soil, as well as the existing shortcomings of soil arch effect, anti-slide pile internal force calculation, landslide thrust calculation and finite element numerical simulation. Anti-slide pile with prestressed anchor cable is analyzed on the research trends of development. Interaction mechanism, time effect, three-dimensional numerical simulation and further optimization design will be the key research direction.

3-D Numerical Study of Mechanical Behaviors of Pile-Anchor System

Mechanical behaviors of pile-soil effect and anchor-soil effect are significantly important in supporting engineering activities of foundation pit. In this paper, finite difference method (FDM) was utilized to perform the numerical simulation of pile-anchor system, composed of supporting piles and pre-stressed anchor cables. Numerical simulations were on the basis of the foundation pit of Jinan’s West Railway Station, and 3D simulation analysis of foundation pit has been prepared during the whole processes of excavation, supporting and construction. The paper also analyzed the changes of bending moments of piles and axial forces of cables, and discussed mechanical behaviors of pile-anchor system, through comparisons with field monitoring. The results show that the parameters concluding vertical gridding’s number, cohesion of pile and soil, and pile stiffness have robust influences on supporting elements’ behaviors. Mechanical behaviors of supporting pile and axial forces of anchor cable changed dramatically, indicating that the potential failure form was converted from toppling failure to sliding failure.

Failure Mechanism of Unbonded Prestressed Thru-Anchor Cables: In Situ Investigation in Large Underground Caverns

Prestressed rock anchor cables are commonly utilized in geotechnical and mining engineering (Peliua et al. 2000; Tezuka and Seoka 2003; Koca et al. 2011) because their installation increases the effective strength and stability of the reinforced rock (Maejima et al. 2003; Li et al. 2012). Nevertheless, in some cases, prestressed cables have failed in large underground caverns or tunnels because of excessive deformation of the anchored rock mass or inadequate assumptions used when designing the cables (Li 2004; Lu et al. 2011; Gong et al. 2011). During the failure process of anchor cable, the stress redistribution and progressive deterioration of the reinforced mass rock can adversely affect the overall stability of the free surface, manifested as large deformation or indeed collapse of rock mass (Galvez et al. 2006; Zhu et al. 2010). Therefore, a deeper understanding of the mode and mechanism of prestressed anchor cable failure will better inform the design process of anchor cables to mitigate future failures. Prestressed anchor cables can be categorized into three general groups based on the anchoring method (Jarred and Haberfield 1997; Chen and Yang 2004): (1) tip-grouted anchor cables that have grout-bonding segments and free segments; (2) fully grouted anchor cables with anchor wires that are fully bonded with the rock; (3) prestressed thru-anchor cables that have two anchor bases without grout-bonding segments. The tip-grouted and fully grouted prestressed cables have been the subject of research more than the thru-anchor cables because they have more extensive applications (Spang and Egger 1990; Hyett et al. 1995; Serrano and Olalla 1999; Huang et al. 2002; Cai et al. 2004; Ugur et al. 2011). Even less attention has been paid to the unbonded prestressed thru-anchor cables (UPTACs) based on the limited information available in the academic and professional literature. The mechanical interactions of UPTACs are different from those of groutbonding cables because the UPTAC does not have a groutbonding section, but has two anchor bases. Under loading, the prestressed cable can restrain the deformations of the anchored rock, and the anchored rock can also transfer the rock stress to the cable via the bridge of anchor bases. This paper focuses on evaluating the failure mechanism of UPTACs based on a case study of underground caverns in Sichuan Province, China. Several external failure modes of the UPTACs observed in this project are first presented and special design techniques for the UPTACs in the large underground caverns are summarized based on in situ investigation: failure depth of disabled UPTACs, break face, measured working load and installation method.