Anchor Rod Research Articles

Evaluation and Deformation Control Study on the Bias Pressure of Layered Rock Tunnels

In the process of tunnel construction, the bias of layered rock mass tunnels has always been a prominent problem that troubles the construction and safe operation of tunnels. In this paper, a comprehensive method that combines monitoring technology and discrete element (3DEC) numerical simulation is proposed to analyze the deformation characteristics of the surrounding rock in the layered rock tunnel and the deformation law of the bias tunnel. The results indicate that the tunnel surrounding rock deformation in the study area showed the characteristics of bias. Based on the bias mechanism, the surrounding rock deformation law, the construction deformation control, and the optimization measures of layered rock mass in the bias tunnel were studied by means of combining monitoring technology with discrete element (3DEC) numerical simulation. Based on the research results, appropriate methods for controlling the deformation of the surrounding rock of the tunnel with comprehensive consideration of the anchor rod length, anchor rod angle, and anchor rod layout spacing were proposed. The method proposed in this paper could visually reveal the deformation characteristics of the surrounding rock of layered rock tunnels and the deformation law of bias tunnels. It could also better solve the problem of deformation control in the tunnel construction process. This approach provides a novel idea for special layered rock mass tunnel bias evaluation and deformation control parameter optimization and serves as a valuable reference for analogous engineering cases through engineering case analysis.

Research on Coal Bolt Grouting and Solidification Technology for Increasing the Drainage Concentration of Along-bed Boreholes

In order to increase the coal seam’s along-bed drilling concentration and to prevent roof leakage in roadways, the test has carried out research on coal bolt grouting and solidification to increase the along-bed drilling concentration. The results of the field investigation show that the coal After the body is grouted and solidified, it presents a shape similar to a cement block. The slurry enters the cracks of the coal body and forms a stronger whole after solidification. No roof leakage occurred in the coal roadway in the solidification section, and the roadway integrity was well controlled. After the anchor rod is grouted and solidified, the concentration of gas drainage in bedding boreholes is generally higher. The concentration of gas drainage in the initial drilling of the test group was 30% to 60%, and the average drainage concentration during the investigation was about 40%, and the attenuation was slower than that of the drilling in the control group. The effect of bolt grouting to solidify coal is obvious.

An Experimental Study on heave and Uplift Behaviour of Granular Pile Anchor Foundation System

Several innovative ground improvement techniques were presented by various researchers throughout the globe for modification of the existing poor soils. Granular Pile-Anchors (GPA) were found to be more promising in resisting the heave behavior of the expansive soils in recent times. The engineering behavior of the soil can be improved by this technique apart from resting the swell. This technique is a modification on the existing granular pile technique with an anchor plate beneath the granular pile that is connected to the foundation by means of an anchor rod or cable. Numerous scale model tests were discussed in this paper to understand the heave and pull-out behavior of Granular Pile-Anchor Foundation (GPAF) system. The effect of spacing was studied by using two granular piles at varied spacing. It was observed that the swell potential was reduced to about 68.09% for 50mm dia GPA, compared to the virgin expansive soil. The swell potential was found to be further reduced at twice the diameter of the pile spacing. The pull-out capacity was found to be increased by about 393% by providing a 50mm diameter GPA in the expansive soil.

Experimental study of concrete breakout failure mechanism in an exposed column base with a foundation beam

Exposed column bases are extensively used in low-to-medium rise steel structures. However, the stress transfer mechanism in the column base is extremely complicated at various failure modes. One of the failure modes mentioned in the Japanese design recommendations involves the yielding and fracture of anchor rods. To ensure this failure mode, the pull-out failure of the anchor rods—one of the reasons responsible for the concrete breakout failure—has to be prevented. However, in Japan, the current design recommendation regarding the concrete breakout failure is not clear, and the studies that have focused on this topic are limited in number. In this study, experiments were conducted to clarify: 1) the concrete breakout failure mechanism, and 2) the effects of the foundation beam reinforcement on the concrete breakout failure. A total of nine specimens, with varied configurations in anchor rods, foundation beam reinforcement, concrete strength, among others, were loaded to failure. According to the experimental results, the column rebar started to transfer strength after the tension of anchor reached the strength of concrete breakout failure. The current design recommendation overestimates the number of effective column rebars on the concrete breakout failure. As for the contribution of concrete, it decreased as the conical cracks occurred and became stable afterwards. Meanwhile, the foundation beam rebar exhibited negligible effect on the concrete breakout failure. Based on the experimental observations, a stage-wise approach is proposed to quantify the contributions of both the concrete and column reinforcement on the concrete breakout failure of an exposed column base.

Out-of-plane loaded masonry walls retrofitted with oriented strand boards: Numerical analysis and influencing parameters

The computational prediction of the out-of-plane behaviour of unreinforced masonry walls is a challenge. However, computational numerical models may provide, if properly calibrated, a powerful tool to predict the behaviour of new retrofit techniques. This paper presents the Finite Element (FE) modelling of masonry walls retrofitted with oriented strand boards (OSB) aiming the prediction of its out-of-plane behaviour. Such retrofit measure has been proposed by the authors for brick masonry walls and its efficiency has been demonstrated through experimental studies on small-scale and larger-scale masonry specimens (out-of-plane monotonic tests). The data gathered in the experimental phase has been used here to calibrate the numerical FE-based models (i.e. non-retrofitted and retrofitted). For this purpose, a detailed micro-modelling strategy has been followed assuming a perfect bond between mortar joints and brick units. The so-called Concrete Damage Plasticity (CDP) model has been adopted to describe the constitutive relation of the masonry and the OSB timber panel. The connection between the masonry and the OSB panel has been modelled through elastic anchors. Numerical results show a good agreement with the experimental data, in terms of observed damage pattern and capacity curve (within 10% difference). The calibrated numerical model has been instrumental in developing a parametric analysis to study the effect of different OSB thicknesses, the side of the application of retrofit, and the spacing between connections through anchor rods. These revealed that the out-of-plane capacity of the system is directly proportional to the OSB thickness and that the spacing between steel connectors should be lower than 500 mm for an adequate response.

Research on failure criteria and collapse height of roadway roof strata based on energy accumulation and dissipation characteristics

AbstractRoof collapse is a form of rock failure driven by energy release. The rectangular elastic thin plate (RETP) model, widely used in coal mining engineering research, reflects the law of the movement of overlying strata of a coal seam. The stress distribution regularity of each delamination can be analyzed using the theoretical model of RETPs. In this study, a new method for determining both the height of the caving zone and the damaged area of the roadway roof is developed based on the energy evolution law. The damaged area and the oval‐shaped boundary of each stratum are determined using the damage criterion deduced by calculating the strain energy of the elementary volume. As a case study, the collapse height was obtained by accumulating the thickness of damaged strata, and the length of bolts was increased from 2.2 m to 2.8 m, effectively preventing the reoccurrence of a roof collapse for the No. 30102 working face in Nanliang Coal Mine. In addition, the vertical boundary of the caved zone can be outlined by connecting and fitting the end vertexes of the minor axis in the oval‐shaped damaged area of the RETPs. The supporting angle of the bolts in two side walls of the roadway was decreased from 75° to 70°. This method was verified and applied in a roof collapse investigation by determining the length and drilling angle of the anchor rod and anchor cable required to develop reasonable support schemes. The results of this research can be used for ensuring safety in coal mining and subway or tunnel construction in China.

Research on Application of Lattice Anchor System Design and Construction Monitoring in Slope Protection

This article focuses on the application of lattice anchor system in high slope protection. According to the engineering geological characteristics of the slope of the site, combined with the requirements of the layout of the slope of the site, the slope is permanently supported by the combined support system of lattice anchor rods, nets, and soil spray. The example takes the slope under the arc failure mode as the research object to carry out the parameter design calculation, and conducts real-time monitoring during and after the construction. Calculation and monitoring analysis show that it is feasible for concrete lattice anchor system to be used in slope reinforcement projects, and the stable bearing capacity of lattice anchor system is higher, which has higher construction safety and better effect.

Failure mode identification of column base plate connection using data-driven machine learning techniques

Column base plate (CBP) connection is one of the most important structural elements of steel structures since the failure of these base plate connections can result in the collapse of the entire structure. The prediction of failure mode of CBP connection plays a significant role in ductile behavior of the structure which is critical for damage assessment or retrofitting strategies after any natural hazard. This study introduces a rapid failure mode identification technique for CBP connections by exploring the recent advances in machine learning (ML) techniques. A comprehensive database is assembled with 189 available experimental results for CBP connections including various parameters affecting the CBP behavior. To establish the best classification model, a total of nine different ML algorithms such as Support vector machine, Naïve bayes, K-nearest neighbors, Decision tree, Random forest, Adaboost, XGboost, LightGBM, and Catboost are considered in this study. Comparing the developed ML models, the Decision tree based ML model is suggested in this study which has an overall accuracy of 91% for identifying the failure mode of CBP connections. It is also found that base plate thickness, embedment length, and anchor rod diameter are the influential parameters that govern the failure mode of CBP connections. Furthermore, an open-source classification model is provided to rapidly identify the failure mode of CBP connection by allowing modifications for future developments.

Artificial Neural Network-Based System for Location of Structural Faults on Anchor Rods Using Input Impedance Response

Structural faults on anchor rods due to corrosive processes are among the major natural causes worldwide for the collapse of guyed towers. As such towers are widely used on both power transmission lines and antenna systems, their collapse may cause unexpected interruptions of telecommunications and power delivery services. Despite being of utmost importance, underground corrosion monitoring is still a technological challenge, because it is a highly nonlinear problem, influenced by several soil characteristics and its complex iterations with the metallic structure of the rods. Some techniques have already been proposed to locate such faults; however, either they require previous knowledge about the medium or they need the interpretation of the acquired signal by a human specialist. These requirements make it difficult to use such solutions in automatic monitoring as well as to make their integration with Internet of Things (IoT) systems. In this article, a novel technique is proposed to automatically locate structural faults on anchor rods, based on a two-step machine learning (ML) solution. The system is fed by a vector composed of frequency-domain samples of the input impedance electromagnetic (EM) signals measured on the rods through a dedicated designed connector. Experimental results have demonstrated that the proposed combination of EM signal acquisition and ML data processing was able to perform the fault location on anchor rods accurately and with a total independence of any additional human analysis.

Evaluation of correction rates for titanium-alloy and cobalt-chrome-alloy rods in adolescent idiopathic scoliosis

<p><strong>Background: </strong>The customary treatment of AIS is spinal fusion with instrumentation using rigid rods. In parallel, agents such as, curve magnitude, points of fixation, level instrument selection, curve flexibility, kind of anchor rods used for patients and post-operative care are the main factors affecting the outcome of surgery.</p><p><strong>Methods: </strong>A total 50 patients was included in the study. The control group, which included 31 patients treated with Ti rods, was compared with an experimental group of 19 patients treated with CCM rods. Correction surgery was performed through posterior approach using rod-rotation maneuver after inserting a pedicle screw in each vertebrae within the fusion. Six-millimeter CCM and six-millimeter Ti rods were used in experimental and control groups, respectively. Pre and postoperative indices of coronal alignment and sagittal alignment were measured.</p><p><strong>Results: </strong>There was no statistical difference between the two groups for age, sex, Risser’s stage, preoperative Cobb’s angle, type and flexibility of curvature. The correction rate of thoracic curve was 71.4±10.2% for the CCM group and 71.8±6.1% for the Ti group. There were no statistical differences between the two groups for all coronal and sagittal factors (p>0.05).</p><p><strong>Conclusions: </strong>AIS cases with double curvature, there was no statistically significant difference between Ti and CCM rods for coronal and sagittal plane correction rates. The derivations from biomechanical studies do not translate into clinical situations.</p>

Structural Behavior of Prefabricated Ecological Grid Retaining Walls and Application in a Highway in China

The retaining wall is a common slope protection structure. To tackle the current lack of sustainable and highly prefabricated retaining walls, an environmentally friendly prefabricated ecological grid retaining wall with high construction efficiency has been developed. Due to the asymmetrical condition of the project considered in this paper, the designed prefabricated ecological grid retaining wall was divided into the excavation section and the filling section. By utilizing the ABAQUS finite element software, the stress and deformation characteristics of the retaining wall columns, soil, anchor rods, and inclined shelves in an excavation section, and the force and deformation relationships of the columns, rivets, and inclined shelves in three working conditions in a filling section were studied. The study results imply that the anchor rods may affect the columns in the excavation section and the stress at the column back changes in an M-shape with height. Moreover, the peak appears at the contact point between the column and the anchor rod. The displacement of the column increases slowly along with the height, and the column rotates at its bottom. In the excavation section, the stress of the anchor rod undergoes a change at the junction of the structure. The inclined shelf is an open structure and is very different from the retaining plate structure of traditional pile-slab retaining walls. Its stress distribution follows a repeated U-shaped curve, which is inconsistent with the trend of the traditional soil arching effect between piles, which increases first and then decreases. For the retaining wall structure in the filling section, the numerical simulated vehicle load gives essentially consistent results with the effects of the equivalent filling on the concrete column.

Strength characterization of exposed column base plates subjected to axial force and biaxial bending

Exposed Column Base Plate (ECBP) connections are commonly used to connect columns in steel moment frames to concrete footings. Although their response under uniaxial bending and axial force is well established, only limited research and design guidance exists for their response under biaxial bending. A new method is presented to characterize the internal stress distribution and anchor rod forces in ECBP connections subjected to biaxial bending and axial compression. The method is based on (and validated against) finite element simulations on ECBP connections; these simulations are, in turn, validated against experimental data. The proposed method extends the American Institute of Steel Construction’s Design Guide One approach (for uniaxially loaded ECBP connections) to biaxial loading. This involves addressing indeterminacies that arise due to the engagement of additional anchor rods (as compared to the uniaxial case). The proposed method accomplishes this through the enforcement of a predetermined pattern of tensile forces in the anchor rods, in conjunction with a stress block on the compression side. The method is demonstrated to predict anchor forces with good accuracy across a range of configurations (including column and base plate size) and loadings (level of axial force and bending angle). Implications for the design of ECBP connections are outlined along with limitations of the proposed approach.

Research on the Construction Technology for the Reconstruction of Existing Retaining Piles under the Condition of the New and Old Foundation Pits in Close Proximity

In view of the development of the city and the development and utilization of underground space, the new building foundation pit is close to the existing foundation pit. In view of this problem, a common reconstruction technology of existing retaining piles under the condition that the new and old foundation pits are adjacent to each other is proposed. The main construction process includes: primary selection of common pile section, design change, bored pile inspection, construction of steel pipe pile with pilot hole, depth judgment of new and old foundation pit, construction of locking anchor rod, foundation pit construction, monitoring and acceptance, etc. The reconstruction and reuse technology of the existing foundation pit supporting pile has been applied in a foundation pit in Zhuhai, which proves that it is safe and reliable, saves the construction period, reduces the construction difficulty, and improves the construction efficiency, which can provide reference for similar projects.

Military technology in mine rescue

The sense of security is an individual’s one-sided personal expression referring to one’s awareness of existing threats and potential possibilities of their prevention. Thus we can observe a permanent development of technologies developed to meet the needs of military operations aimed at neutralizing threats related to explosives of military origin, as well as any improvised explosive devices. Threats are the events that adversely affect life, health, property or the environment, therefore, the mentioned technologies can be used in the civilian market as well. This article presents military systems that have been developed by Alford Technologies Ltd. (‘The World’s Leading Provider of User-Filled Explosive Chargers and Disruptors’). The systems that have been named ReBar Cutters™ and DIOPLEX™ have been developed to save the lives of soldiers, military equipment and any relevant infrastructure while conducting a wide scope of combat operations throughout the world. The systems can for example be easily used as an alternative support for mining rescue teams during mine rescue operations. The authors intend to present the above-mentioned systems due to their precision, accuracy, and most importantly, because the products are user-filled and therefore can be prepared on site and ready to use very fast. Tests of systems named ReBar Cutters™ and DIOPLEX™ presented in the study were carried out in Zakłady Górnicze Polkowice-Sieroszowice Oddział KGHM Polska Miedź S.A. at a depth of 850 m in order to check their effectiveness in the future environment (pressure, humidity, temperature, dust). The presented shaped charges with cumulative insert were elaborated with explosives used in mining – RIOPRIME 25 (Mini Primer) and ERGODYN 22E – and used for the cut steel structural elements (steel anchor rod), steel leveling cable, sheathed electric mining cable and an element form bucket loader type LKP 903. The tests were not financed, and the obtained results were part of the research in one of the author’s PhD dissertation.

Research on Application of Self-locking Anchor Rods in the Improvement of wind turbine generator tower foundation

This article provides a solution to replace the upper equipment while retaining the foundation during the technical transformation of wind power generation. Due to load changes and the damage and defects of the original foundation ring, the connection method to connect the new wind turbine tower and the existing foundation should be redesigned, and the original wind turbine generator tower foundation should be reinforced accordingly. This paper introduces the scheme of using common self-locking anchor rod and prestressed self-locking anchor rod to connect the upper tower and foundation, and compares the advantages and disadvantages of the two schemes. Two schemes for increasing the foundation and strengthening the foundation with prestressed rock bolts are proposed and compared. Both the ordinary bolt scheme and the prestressed bolt can meet the mechanical properties, but the ordinary bolt construction is convenient and economical; the foundation reinforcement using the prestressed rock anchor scheme is more economical and environmentally friendly.

Study on limit state of retaining wall under different geotechnical structures

On the railway, anchor retaining wall is widely used in rock section in general area, while soil anchor rod is relatively less used. However, with the continuous development of civil engineering, the application of soil anchor is more and more. In this paper, the limit states of anchored retaining walls in sandy soil, clay soil, and rock strata are studied and analyzed. The limit state equation and function of the anchored retaining wall are determined. The reliability index of the bolt retaining wall is calculated by Monte Carlo method. Finally, according to the target reliability index, the partial coefficients of limit state design of anchor retaining wall under various design conditions (sandy soil stratum, clay main stratum and rock stratum) are calculated by general separation method, and the comprehensive partial coefficient obtained is compared with the total safety factor of current code. The limit state design expression of anchor retaining wall under various design conditions is formed.

Investigation of Mechanical Behavior of Steel Column Base Plates

Major earthquakes in the world led engineers and scientists to work on the connections of steel structures. Since the capacities of the connections, which are one of the important components of a steel structure, significantly affect the capacity of the entire structure, scientists are trying to design new connections and determine the limit states of these connections. At this point, column-base plate connections, which are an interface between reinforced concrete foundation and column, are of great importance in steel structures. In this study, the connections designed using base plates with different thicknesses, different numbers of anchor rods and different column types are analyzed under static loads, and comparative results are introduced in terms of stress and deformations occurred on the connection components. Analyzes were performed using ANSYS, a finite element software that is frequently used in engineering disciplines. The results obtained are interpreted and the advantages and disadvantages of the different types of column base plate connections are revealed. The results of the research show that the thickness of the baseplate used in the connection has a significant effect on the total deformation and stresses on the connection and its components. In addition, it has been determined that the number of anchor rods used in the base-plate connections affects the deformation and stresses. It has been observed that the total rigidity of the connections has a dominant role in the mechanical behavior of the joints.

Using composite yield mechanism to mitigate seismic damage to exposed steel column base connections

A novel exposed column base (ECB) connection, featuring composite yield mechanism (i.e., a combination of anchor rod and base plate yielding), has been recently proposed in Japan for optimum seismic performance. This paper focused on investigating the effects of using composite yield mechanism on damage mitigation for ECB connections. In doing so, four two-thirds scale specimens, with different base connection configurations, were tested under combined flexure and axial load. Their performances were assessed and compared in terms of damage evolution, moment-rotation relationship and energy dissipation. The experimental results showed that for ECB connection with composite yield mechanism, both anchor rod and base plate will actively contribute to the moment resistance and energy dissipation. This can successfully postpone the interior anchor rod yielding and fracture, compared to the ECB connection with anchor rod yield mechanism. Meanwhile, the strain demands on exterior plate can be also released compared to the ECB connection with base plate yield mechanism. The relative contributions from anchor rod and base plate of ECB connection with composite yield mechanism can be controlled by changing the exterior plate thickness. In addition, an analytical method was proposed to predict the yield and ultimate moment strength for the Composite Yield ECB connection based on the principle of virtual work. The difference between predicted and measured moment strength is within 15%, showing the validity of the proposed method for moment strength prediction.

Study on Mechanical Characteristics of Energy-Absorbing and Anti-Scour Bolts

In order to improve the impact resistance and mechanical performance of anchor rods and satisfy the requirements for supporting rockburst roadways, the energy balance equation of the energy-absorbing support and roadway surrounding rock system is established. Moreover, to effectively prevent rockburst disasters, the energy criterion for roadway instability is derived. From the perspective of an energy-absorbing support, a yield-absorbing anti-shock anchor composed of a rod body, tray, constant resistance energy-absorbing device, and special-shaped nut is designed and developed; compared with ordinary anchor rods, this rod has stronger mechanical properties for resisting impact. Theoretical and numerical simulation studies show that the energy-absorbing device has a repeatable deformation failure mode and a constant yield force. The paper also presents the principle involved in the design of anti-shock bolt supports. The energy-absorbing support not only effectively guides and controls the release and conversion of impact energy but also consumes the impact energy in the buffering process of the anchor to ensure the stability of surrounding rock and support protection system. This study aims to provide reference for roadway support design and to improve rock bolts used in rockburst roadways.

Theory and full-scale simulation testing of the mechanical properties of anchors under a variable lateral pressure coefficient

The mechanical behavior of the lateral pressure coefficient (LPC) of the axial stress of the anchor rod is an important factor in roadway bolt support, especially in deep mining, where the variation of the LPC is larger. In this paper, an innovative mechanical model of bolt pulling is proposed in which the influence of the LPC is considered. When the LPC is changed, the variation of the axial force along the anchor rod body is expressed by the interface normal stress of the anchoring system. In addition, a full-scale test model with a 1:1 similarity ratio was developed in the laboratory and the influence of the LPC on the deformation and stress of the anchor rod under vertical and horizontal pressure was studied by using a 2.5-m fiber Bragg grating (FBG) force-measuring anchor rod. The results demonstrate that the axial force of the bolt shows the same increasing trend under various LPC values. The theoretical solution of the bolt axial force variation value accords with the experimental data. The theoretical calculation method can effectively predict the variation distribution of the bolt axial force under various LPC changes. Increasing the LPC of the surrounding rock can effectively reduce the axial force and the deformation of the bolt under the same pulling force. The support effect of the bolt can be improved by increasing the pressure of the anchor hole and increasing the interface friction coefficient between the anchoring agent and the surrounding rock during the construction of the bolt support.