Anchor Beam Research Articles

Study on Support Technology of Truss Anchor Cable Beam in Deep Soft Rock Roadway Excavation

Aiming at the difficult problem of soft rock roadway support in deep mine, the support mode of "truss anchor beam" is proposed, and the support mode technology of truss anchor beam in deep soft rock roadway driving is studied by FLAC simulation software. Combined with the measured displacement of coal and rock around underground roadway under this support mode, it is concluded that the truss anchor beam support mode can introduce the high stress of shallow coal and rock around roadway into deep area, thus effectively controlling the deformation of coal and rock around roadway and ensuring safe and efficient production of mine.

Analysis and prediction of compressive and split-tensile strength of secondary steel fiber reinforced concrete based on RBF fuzzy neural network model.

Accurate analysis of the strength of steel-fiber-reinforced concrete (SFRC) is important for ensuring construction quality and safety. Cube compression and splitting tensile tests of steel fiber with different varieties, lengths, and dosages were performed, and the effects of different varieties, lengths, and dosages on the compressive and splitting properties of secondary concrete were obtained. It was determined that the compression and splitting strengths of concrete could be effectively improved by the addition of end-hooked and milled steel fibers. The compressive and splitting strengths of concrete can be enhanced by increasing the fiber length and content. However, concrete also exhibits obvious uncertainty owing to the comprehensive influence of steel fiber variety, fiber length, and fiber content. In order to solve this engineering uncertainty, the traditional RBF neural network is improved by using central value and weight learning strategy especially. On this basis, the RBF fuzzy neural network prediction model of the strength of secondary steel fiber-reinforced concrete was innovatively established with the type, length and content of steel fiber as input information and the compressive strength and splitting tensile strength as output information. In order to further verify the engineering reliability of the prediction model, the compressive strength and splitting tensile strength of steel fiber reinforced concrete with rock anchor beams are predicted by the prediction model. The results show that the convergence rate of the prediction model is increased by 15%, and the error between the predicted value and the measured value is less than 10%, which is more efficient and accurate than the traditional one. Additionally, the improved model algorithm is efficient and reasonable, providing technical support for the safe construction of large-volume steel fiber concrete projects, such as rock anchor beams. The fuzzy random method can also be applied to similar engineering fields.

Anchor Beams with Needles. An East Anglian Mystery

In central north Essex and central south Suffolk there are a number of houses dating from the fifteenth to seventeenth centuries with a form of anchor beam where, unlike those in Denmark and a number of north European countries, the protruding end is not reduced to a tenon that goes through a post, but passes through the wall undiminished with a long wedge, called here a needle, through its protruding end. These anchor beams are not attached to a post or stud but are supported by a rail. Most appear to be sixteenth or, more likely, seventeenth century, and in most cases are used either to insert a floor into an open hall of a medieval house, or of a transitional house built with an open hall heated by a chimney, or simply to remove the need for tiebeams blocking access on the first floor of low buildings. Some do act as anchor beams holding up the side walls. Apart from a few outliers, the list descriptions in the Historic England National Heritage List for England (NHLE) suggests these beams are mostly confined to north Essex and south Suffolk.

Coal Pillar Size Determination and Surrounding Rock Control for Gob-Side Entry Driving in Deep Soft Coal Seams

In response to the large-scale instability failure problem of designing coal pillars and support systems for gob-side entry driving (GSED) in high-stress soft coal seams in deep mines, the main difficulties in the surrounding rock control of GSED were analyzed. The relationship between the position of the main roof breaking line, together with the width of the limit equilibrium zone and a reasonable size for the coal pillar, were quantified through theoretical calculations. The theoretical calculations showed that the maximum and minimum widths of the coal pillar are 8.40 m and 5.47 m, respectively. A numerical simulation was used to study the distribution characteristics and evolution laws of deviatoric stress and plastic failure fields in the GSED surrounding rock under different coal pillar sizes. Theoretical analysis, numerical simulation, and engineering practice were comprehensively applied to determine a reasonable size for narrow coal pillars for GSED in deep soft coal seams, which was 6.5 m. Based on the 6.5 m coal pillar size, the distribution of deviatoric stress and plastic zones in the surrounding rock of the roadway, at different positions of the advanced panel during mining, was simulated, and the range of roadway strengthening supports for the advanced panel was determined as 25 m. The plasticization degree of the roof, entity coal and coal pillar, and the boundary line position of the peak deviatoric stress zone after the stability of the excavation were obtained. Drilling crack detection was conducted on the surrounding rock of the GSED roof and rib, and the development range and degree of the crack were obtained. The key areas for GSED surrounding rock control were clarified. Joint control technology for surrounding rock is proposed, which includes a combination of a roof channel steel anchor beam mesh, a rib asymmetric channel steel truss anchor cable beam mesh, a grouting modification in local fractured areas and an advanced strengthening support with a single hydraulic support. The engineering practice showed that the selected 6.5 m size for narrow coal pillars and high-strength combined reinforcement technology can effectively control large deformations of the GSED surrounding rock.

Superimposed Stress Calculation of Soil Underlying Anchor Beam considering Anisotropy and Strength Nonhomogeneity

Prestress anchor beams are an important reinforcement method for underground engineering and rock slopes, and they are crucial for maintaining the stability of civil engineering structures. In this study, the computational formula of superimposed stress of soil underlying an anchor beam was proposed in this paper, based on the assumption that the anchor beam is completely rigid and the prestress of the anchor cable is acting on soil in the form of a strip uniform load. By considering the anisotropy and strength nonhomogeneity of the saturated soft clay, the failure envelopes of the soil and the maximum effective depth underlying the anchor beam were obtained by the D-P yield criterion suitable for soft clay analysis. Furthermore, the experimental comparisons with the previous findings were used to validate the proposed approach. The proposed method was valid to assess the maximum effective depth. Considering the influence of the factors on the failure envelopes of soil, a parametric study was carried out to optimize the design of the prestressed anchor cable. The findings of this study provide a theoretical basis for designing prestressed anchor cables; these can also be used to predict the response of prestressed anchor cables as well as to optimize the design of the cables, such as the anchorage length of cable and grouting radius.

A Numerical Investigation on the Limitations of Design Equations for Steel Plate Shear Walls

In previous studies various design issues on steel plate shear wall (SPSW) systems under lateral loading were investigated using analytical and experimental methods. However, these studies tried to examine the interactive effect of only a few of design parameters, such as panel aspect ratio, column flexibility parameter, axial load ratio on the boundary frame columns, web plate thickness, stiffness of horizontal and vertical boundary elements and top anchor beam, etc., on the drift capacity and shear force distribution among frame and panel components of SPSWs at a time. This study investigates the effect of all of these parameters in the same framework. A parametric study is conducted on finite element models of 292 3-story SPSWs with rigid beam-to-column connections and designed for specified parameters. By evaluating failure forms from finite element analyses, the limiting (undesired) cases resulting from different combinations of specified geometric properties are identified. A column flexibility factor of 2.2 is proposed instead of the current limit value of 2.5 for satisfactory column performance, improved drift capacity and balanced strength distribution among frame and panel of SPSW. The value of 0.75 for the ratio of plate shear force to total shear force has emerged as a critical threshold value for the strength distribution among plate and frame components in order to conform capacity design principles. This study provides a comprehensive look on the behavior of SPWS for determining the most suitable combination of various parameters in the design of SPSW structures.

Study on timing sequence control fracture blasting excavation of deep rock masses with filled joints

During the blasting excavation of deep underground caverns, the effects of the structural surface on crack propagation are usually considered in addition to the clamping effects of high in situ stress. Based on the notched borehole and timing sequence control (TSC) fracture blasting method, this paper studies the effects of different borehole shapes on the degree of damage of the surrounding rock and profile flatness of the rock anchor beams and the effects of different filled joint characteristics on the blasting crack propagation rules. The results show that the damage depth of the surrounding rocks by round hole smooth blasting is approximately twice that by notched hole smooth blasting, by which the profile formed is flatter. The notched primary borehole (PBH) remains a strong guidance for crack propagation in a rock mass with filled joints, while the stress concentration effects of the round target borehole (TBH) cannot fully guide the cracks until they fall within a certain distance between the PBH and TBH. It is favourable for cracks to propagate along the lines between boreholes with larger filled joint strengths and larger angles between boreholes.

Research on Cumulative Damage Characteristics of Rock Anchor Beam Concrete Supporting Structure by Blasting Vibration of Underground Powerhouse

Aiming at the dynamic disturbance problem of the upper rock anchor beam concrete support structure caused by the blasting excavation of the lower rock mass of the underground powerhouse of the hydropower station, the dynamic finite element software was used to numerically simulate the cumulative damage characteristics of the rock anchor beam concrete structure under multiple blasting, which aims to study the effect of blasting times and blast center distance on the cumulative damage characteristics of rock anchor beam concrete structures in two directions at different ages. The results show that 7 days after the completion of the concrete pouring of rock anchor beam, the damage and destruction effects are produced under the single blasting action. 28 days after the completion of the concrete pouring, there is basically no damage and destruction under the action of five times of blasting. 14 days after the completion of the concrete pouring, the growth process of the cumulative damage effect of the rock anchor beam concrete structure under the disturbance of the blasting excavation of the underground powerhouse shows nonlinear increasing characteristics with the increase of blasting times and nonlinear decreasing characteristics with the increase of blasting center distance. The cumulative damage of rock anchor beam along and perpendicular to the axis of powerhouse conforms to the relationship of cubic polynomials with the blasting times, which also conform to the relationship of quartic polynomial and quadratic polynomial, respectively, with the blast center distance.

Numerical Investigation on the Ground Response of a Gob-Side Entry in an Extra-Thick Coal Seam

This study was aimed at the large deformation phenomenon of rock mass surrounding the gob-side entry driven in a 20 m extra-thick coal seam. Taking tailgate 8211 as the engineering background, a numerical investigation was employed to analyze the deformation law of the gob-side entry. The study results are as follows. (1) Because the immediate roof was composed of weak coal mass with a thickness of 17 m, the roof coal mass was vulnerable to fail with the effect of overlying strata pressure; thus, a visual subsidence of roof coal mass with a maximum convergence of 800 mm was observed in the field. (2) The bearing capacity of the coal pillar was significantly less than that of the panel rib, resulting in the pillar failing more easily under the ground pressure and then generating large-scale squeezing deformation. (3) The roof and panel rib were in a state of shear failure with a failure depth of about 5 m. The coal pillar was entirely in a state of plastic failure. (4) A support scheme including an asymmetric anchor beam truss, roof angle anchor cable, and anchor cable combination structure was proposed. The field work confirmed that this support scheme could efficiently control the deformation and failure of the rock mass surrounding the gob-side entry. This study provides the theoretical basis and technical support for the control of rocks surrounding the gob-side entry in similar conditions.

Strengthening of Burri box Girder Bridge by using External post Tensioning Technology (Sudan)

Ageing, and increasing traffic loads, has become a major problem into today bridge industry. These bridges go deficiency in its Load Carrying Capacity from ageing, exhibited in excessive deformation which renders the bridge usage to an unacceptable level. These will either, impose traffic restriction, or upgrading the existing bridges to defy these adverse conditions. At Burri Bridge, after 33 years on operation, signs of ageing showed in the excessive deformation and the departure of the deformed shape of the super structure from the design profile, and travelling along the bridge was un-comfortable and difficult trip riding. The Objective was to explore the strengthening of the Burri Bridge by using external post tensioned tendons to mitigate the ageing effects and to elevate the capacity of the bridge. It was requisite to examine the bridge before the application of external tendons to insure the stresses in its past status will qualify it for repair. Hence, the present study contains the analysis of the Bridge superstructure in two stages. The first is done in its Past status, and the second when external tendons are added to boost its capacity and defy the effect of past load level, and a new standard load tested. The model was analyzed using Midas Civil software. The study includes the design of the anchor beams where the fresh external tendons are terminated. The study proved that, the capacity of the Bridge is increased by 4.6 %, and this is interpreted in the increase of the Ultimate Flexural Strength and the decrease of the deformation after adding these external tendons. Some of the Techniques implemented are presented.

Effect of principal stress rotation on the stability of a roadway constructed in half-coal-rock stratum and its control technology

Engineering disturbance-induced adjustment of the stress field in the surrounding rock is the main reason that leads to dynamic disasters in deep rocks. This study selected the mining roadway in the No. 92125 working face of the Chacheng Coal Mine as the engineering background for in-depth and systematical analysis on the principal stress path and the changes in the principal stress direction of surrounding rocks under excavation-induced disturbance and the resultant damages. Results demonstrate that the fracture planes were along the direction of intermediate principal stress under true triaxial tests and the internal cracks in the rock strongly depend on the direction of the intermediate principal stress. Therefore, variations in the stress path of the roadway surrounding rocks can cause dramatic changes in their fracture characteristics (direction of rupture). The same results were found for the analysis: the variation of the direction of principal stress on the surrounding rocks in the roadway created adverse effects, which thus triggered great damages. The areas of roof and the shoulder angle, etc. were strongly affected by the principal stress rotation, and the damage caused was obvious. According to the damage characteristics of the surrounding rocks caused by the principal stress rotation during excavation in half-coal-rock roadway, the idea of strengthening support in key areas was proposed, and a high-strength pre-tension support scheme using anchor beam, nets, and cables was proposed. Finally, field measurement results of displacement on the surface and in surrounding rocks reveal that using the optimized supporting scheme effectively controlled deformation in the roadway, ensuring stability of the roadway and meeting engineering requirements.

A simple model for nonlinear analysis of steel plate shear wall structural systems

SummaryThis paper presents a simple and efficient analytical model for nonlinear response analysis of steel plate shear wall (SPSW) structural systems. The proposed model combines individual contributions of the boundary frame and the infill plate. It includes a nonlinear spring element that simulates the global response of the infill plate. The load‐deformation characteristic of this element is defined by a backbone curve and the pinched oriented Ibarra–Krawinkler hysteretic model. SPSW panels in the proposed model are differentiated as intermediate and end panels with two different backbone curves. Based on the theory of pure diagonal tension and experimental data, a basic backbone curve is first developed for the intermediate panel. For the end panel where the strength and stiffness of the infill plate are adversely affected by the flexibility of the anchor beam (the horizontal boundary element at the free end), the basic backbone curve is modified using appropriate strength and stiffness reduction factors. These factors are found by incorporating the strain energy of the anchor beam in the strain energy formulation of the theory of pure diagonal tension. Experimental results on several large‐scale SPSW specimens indicate that the proposed model reliably predicts the hysteretic behavior of SPSW structural systems.

Position tracking and dynamic control of an innovative anchor beam supporting robot

Position tracking modeling and automatic control of an innovative anchor beam supporting robot are presented. Specifically, the forward and inverse kinematics model integrated with BP neural network and the mechanical-hydraulic co-simulation model based on ante-valve pressure compensation method are developed and applied. The experimental system is built to verify the models and method. The results show that position tracking precision can reach the sub-centimeter level. The influence of variable load on hydraulic flow control is weakened effectively and the stability and controllability of load sensitive system is improved. The developed model and control approach are valuable for virtual development and automated testing during the commissioning of hydraulic manipulator.

Effects of frame beam on structural characteristics of artificial soil on railway cut‐slopes in southwestern China

AbstractCut‐slope restoration technologies commonly used in southwest China mainly include using simple outside soil spray seeding (OSSS) techniques, or OSSS combined with an anchor frame beam. Artificial soil used in OSSS can establish a soil layer suitable for revegetation; the addition of an anchor frame beam not only fixes soil and shallow rock, it also acts to strengthen deep rock. However, there have been few studies on the effects of frame beams on artificial soil structural characteristics on railway cut‐slopes. In order to evaluate the effects of different frame beams on artificial soil structure, soil samples from a natural slope (NS) and three cut‐slopes restored using OSSS with various frame beams (AS, arched slope; DS, diamond slope; and RS, rimless slope) were analyzed. Soil structural characteristics analyzed include particle‐size percentage and cumulative distribution curve of dry‐sieving and wet‐sieving aggregates, structural failure rate, water stability factor, soil particle size distribution (PSD), bias and peak convex coefficients, fractal dimension of PSD (Dm), and fundamental properties. Our results indicate that structural failure rate, water stability factor, fractal dimension of PSD, soil bulk density, total porosity, moisture content, and organic matter are significantly affected by the use of different frame beams. In addition, a difference in wet‐sieving soil aggregates content, PSD, clay and sand particle contents, Dm, and the area difference ΔS of cumulative distribution between AS and DS was evident. Overall, soil structure in cut‐slopes using a diamond frame anchor beam recorded the best levels of recovery after 8 years of ecological restoration.

Study on Dynamic Response of Pressure Type Anchor and Lattice Beam System Under Seismic Loadings

In order to investigate dynamic response of anchoring landslide under seismic loadings with different loading magnitudes, a large scale shaking table model test was carried out, and the acceleration response of anchoring landslide, mechanical characteristics of anchors and lattice beams were studied respectively. The test results indicate that (1) under lower loading magnitude 0.05–0.2 g, the PGA amplification factors of different soil layers in landslide, and the dynamic response in different layers of anchors and lattice beams all have little differences. (2) Under 0.2–0.4 g, the PGA amplification factors of different soil layers and the anchoring force of different layers of anchors continue to increase. The strain of the top anchors and the bending strains of the top crossbeams are slightly greater than that in other layers. (3) Under high loading magnitude 0.4–0.6 g, the strain of the upper anchors continues to increase and it is much greater than that in other layers, and the bending strain of the top crossbeam increases sharply and generates obvious tension-bend deformation.

Experimental study on anchoring of FRP-strengthened concrete beams

This study aims at determining an effective technique for anchoring reinforced concrete beams strengthened using FRP composites. Fourteen reinforced concrete beams were cast and strengthened with FRP. Twelve of them were anchored using three different techniques: FRP anchor; bolted steel plates ancho, and FRP sheet and bolted steel plate’s anchors, and two beams were unanchored and left as a control. The beams then were tested under four-point bending to assess their structural performance in terms of failure modes, and load-displacement relations. The experimental results have clearly shown that the unanchored beams suffered from premature debonding failure, while the FRP-anchored beams experienced concrete cover separation failure, and the presence of end anchorages in the bolted steel plates and FRP sheet and bolted steel plate’s anchor's beams had shifted the failure mode to a less critical one. The anchored beams showed an increase in the ultimate load-carrying capacity accompanied by a reduction in mid-span deflection in different percentage with respect to the control beam. It was also observed that the FRP and/or steel U-jackets increase the shear capacity of the anchorage zone, therefore result in higher anchorage efficiency of FRP-strengthened concrete beams. The results also revealed that the FRP sheet and bolted steel plate’s anchors U configuration was the best anchorage system in terms of the structural performance factor. Developing an anchor system to prevent plate end debonding failure is vital for the successful design of strengthening systems using FRP composites.

Large deformation evolution and failure mechanism analysis of the multi-freeface surrounding rock mass in the Baihetan underground powerhouse

In a large underground powerhouse, the surrounding rock mass at the intersection of the caverns has multiple free faces. This rock mass is more susceptible to stability issues because of its peculiar structure. This paper takes the Baihetan underground powerhouse as a case study example, wherein the failure issue of multi-freeface surrounding rock mass appears prominent. Through analysis of monitoring data from multi-point extensometers, it has been concluded that the average daily deformation of the main powerhouse sidewall on downstream side in the presence of multi-freeface rock mass proves larger than that on upstream side; the maximum deformation reaches 0.48 mm/d, overshadowing that at the rock anchor beam as well. The multi-freeface surrounding rock mass is not only more subject to large deformation but also shows more sensitivity to positional change in the working face. Moreover, the sidewall and rock anchor beam witness greater spatial deformation compared with the arch area from a spatial perspective, and from the point of time the time-related deformation presents a step growth, which tends to eventually converge. The failure mechanism is also discussed, where fiercer stress redistribution and denser cracks account for the greater deformation of the multi-freeface surrounding rock mass. In general, a wide range of underground powerhouse stability issues has arisen with respect to huge-scale and adverse geological conditions since the construction of the Baihetan Hydropower Station, and settling these issues will undoubtedly have milestone significance with regard to the construction and development of hydropower engineering projects among the worldwide.

Mechanism Study on Elevation Effect of Blast Wave Propagation in High Side Wall of Deep Underground Powerhouse

In view of the influence of blasting excavation in the deep burial underground powerhouse on the dynamic disturbance and blasting vibration of side wall and surrounding rock, the blasting vibration test method is often used for on‐site monitoring and control. Taking the blasting excavation of the high side wall of an underground powerhouse of a hydropower station as the engineering background, a long‐term blasting vibration test is carried out on the site. The measuring points are arranged along the elevation direction and horizontal direction of the high side wall of the powerhouse. Through analyzing and comparing the blasting vibration velocity values extracted from a large number of on‐site measured data in the elevation direction, an interesting phenomenon is found. The measured vibration velocity of the rock anchor beam in the area far away from the blasting is greater than that in the area near the blasting, and the vibration velocity after the casting of the rock anchor beam is greater than that before the casting. In order to avoid the randomness and contingency of the measured data, based on the blasting parameters, loading quantity, and rock mechanical characteristics used in the field, the elevation effect of the numerical model of the underground powerhouse is established by using the dynamic finite element software. By comparing the numerical simulation and the on‐site monitoring of the elevation direction vibration velocity at the same location, it is found that the two have the same law, which verifies the reliability of the numerical calculation model. By changing the elevation and horizontal distances to select the measuring points in the numerical model, the propagation curve of the blasting vibration of the high side wall of the underground powerhouse in the elevation direction is obtained and the wave propagation phenomenon and the local elevation amplification effect of blasting vibration velocity in the side wall of the powerhouse are found. By means of changing the morphology characteristics of the rock anchor beam, a numerical calculation model of the rock anchor beam before casting is established, and the blasting vibration velocity in the elevation direction of the same measuring point as the original model is extracted. The analysis and comparison results show that the “whiplash effects” caused by the reflection superposition of the convex morphology characteristics of the rock anchor beam on the blast wave and the vibration response of the rock mass at the step part is the main factor for the elevation effect. The fluctuation phenomenon of the vibration velocity in the elevation direction is caused by the natural frequency and the main vibration mode of the high side walls, and the reflection superposition of the convex geomorphology characteristics of the rock anchor beam will aggravate this fluctuation phenomenon. Therefore, in the construction of deep underground powerhouses, attention should be paid to the blasting construction and support design of the rock anchor beam.

Piezoelectric Bulk Mode Disk Resonator Post-Processed for Enhanced Quality Factor Performance

This paper presents a bulk-mode disk resonator utilizing a transverse piezoelectric actuation technique to drive the single crystalline silicon disk structure in its wine-glass bulk mode of resonance. The device is fabricated by post-processing dies from a commercial microelectromechanical systems process and combines high quality factor and relatively low motional resistance. Post-process fabrication steps are used to reduce the width of the anchor beam supports, and consequently reduce the anchor losses. This results in a factor of 3 increase in the quality factor. Post-processed resonators were measured to have resonance frequencies of 23 MHz and quality factors of 13000 in atmospheric pressure, increasing to 31000 in 1 mTorr vacuum. The devices also demonstrate motional resistances of 21 kQ in atmospheric pressure, reducing to 8.8 kQ in 1 mTorr vacuum without requiring any dc voltage for operation.

An Investigation of Structural Dimension Variation in Electrostatically Coupled MEMS Resonator Pairs Using Mode Localization

If a pair of MEMS resonators is electrostatically coupled together, the vibration amplitude ratios at the resonant frequencies of the resulting coupled system are sensitive to stiffness perturbation. An imbalance between the two resonators causes the confinement of vibration energy when the system is resonating, an effect known as mode localization. The degree of localization can be determined by extracting the amplitude ratio of the resonators through capacitive transduction. In this paper, we have fabricated MEMS devices, using a dicing-free silicon-on-insulator process, consisting of pairs of closely spaced microresonators. Each resonator consists of a clamped–clamped beam with a wider section in the middle, which is the location of the electrostatic coupling, instituted through the dc biasing of the resonators. Several devices have been fabricated, with the length of the anchor beams being varied, which influences the frequency of resonance. Stiffness imbalance between the resonators has been introduced through electrostatic spring softening, with the sensitivity of the amplitude ratio of the resonant-mode shape being greater for the higher frequency, shorter anchor devices. The sensitivities of the devices in this paper have been found to be nine times greater than the state-of-the-art two-degree-of-freedom mode-localized sensors.