A theoretical analysis and experimental verification of the stress distribution in prestressed steel-strand anchor cables over their entire length were conducted in this study combining ...quasi-distributed embedded FBG sensing, prestress loss principles and fundamental deformation theory. Four series of steel-strand anchor cable pull-out tests were conducted with variable free section lengths, anchorage lengths and strain monitoring point locations. A difference not exceeding 2 % between the stress in the anchor cable free section measured by the quasi-distributed FBG sensors and the theoretical values calculated considering concrete prestress loss was observed. A relationship between the effective anchorage length and the effective prestressing force was deduced from the stresses recorded by the FBG sensors in the cable anchorage section. Combined with the fundamental theory of deformations, the stresses in the anchorage section were then calculated and compared with the experimental values. The errors generally did not exceed 10 %.
•Provide the basis for the design of the FBG measurement point when monitoring the stress performance of anchor cable: The anchor cable pull-out test was designed according to the theory and the change of three parameters. The test data are valid and show good regularity, which provides a reference and basis for FBG layout when monitoring the anchor cable.•Provide a calculation basis for the determination of tensioning control stress during the tensioning of anchor cable construction and the measured value of effective prestress. Prevent quality problems such as strand breakage due to excessive tensioning control stress and failure to achieve reinforcement effect due to insufficient effective prestress.•Discovered the measured stress values of anchored sections of anchor cables and the variation of anchorage length with tension-controlled stresses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The traditional anchor cable has limited deformation, which can be exceed easily in the slope reinforcement. In order to adapt to the slope reinforcement under complex geological conditions, a ...high-strength and large-deformation anchor cable is proposed. The anchor cable is characterized by high tonnage and large deformation. Its yield device consists of several yield sets, which are of the squeeze friction type. The initial yield force and stroke of the anchor cable can be adjusted according to the design. Laboratory tests of yield sets are carried out. Three types of yield sets that meet the requirements are found. Their initial yield strengths are 120 kN, 135 kN and 145 kN, and their yield strokes are greater than 200 mm. The test results show that the output force has a linear relationship with the length of the yield interface. Its working principle is clarified, and the key parameter calculation method is proposed. The yield anchor cables of 400 kN, 500 kN, 1 000 kN and 1 500 kN class are successfully d
To examine the disparity in deformation behavior and mechanical qualities between anchor cables with C-shaped tubes and regular anchor cables under shear conditions. The double-sided shear tests of ...free-section anchor cables and anchor cables with C-shaped tubes were conducted utilizing the indoor large-scale double-shear test equipment with varying pretension loads. The indoor double-shear tests indicate that the inclusion of the C-shaped tube alters the stress distribution of the anchor cables inside the anchor cables with C-shaped tubes and mitigates the impact of stress concentration. Moreover, it facilitates the transition of the anchor cable's failure mode from a mix of tensile and shear breaking to mainly tensile breakage. In addition, ABAQUS finite element analysis software was used to establish a double shear test model of the anchor cable with C-shaped tube to accurately simulate the interaction and stress distribution among the anchor cable, C-shaped tube, and concrete block in the double shear test. The findings of the simulation results reveal that the numerical model can adequately depict the evolution of the stress distribution in the prestressed anchored structure and the damage of the concrete block with increasing shear displacement. The relational equation for the yield state of the anchor cable with C-shaped tube under combined tensile and shear loads is found by integrating the experimental and simulation data, the static beam theory, and the concept of minimal potential energy.
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•- The new material cable (CREAC) with high energy absorption property is developed.•- The mechanical and energy absorption characteristics of CREAC are clarified.•- The design method ...of CREAC is established and applied in the field.
During the construction of underground engineering projects, it is often confronted with complex conditions such as high stress, extremely soft rock, and strong disturbance, resulting in stress concentration and energy accumulation in the surrounding rock. Due to insufficient elongation and low safety margin, it is difficult for common anchor cables to effectively absorb the energy released from the rock deformation, which often results in the failure of the supporting structure. To this end, a new material constant resistance energy-absorbing anchor cable (CREAC) is developed with high elongation and high energy absorption properties. To study the mechanical and energy absorption properties of the new anchor cable, the static tensile and dynamic impact tests are conducted. The results between CREAC and structural constant resistance and large deformation anchor cable (CRLDC) are compared. In terms of static mechanical properties, the maximum elongation of CREAC is 16.2%. Based on the commonly used cable length of 10 m in the field, the maximum elongation and the energy absorbed by CREAC are 2.21 times and 2.76 times that of CRLDC, with good static deformation and energy absorption capabilities. In terms of dynamics properties, the average single impact deformation of CREAC is reduced by 88.7% compared to CRLDC, and the energy it can absorb is 7.43 times that of CRLDC, showing advantages in impact deformation resistance and energy absorption. The design method of the constant resistance energy-absorbing support is proposed and the field application of CREAC is carried out. The monitoring results confirm that this new material anchor cable can effectively control the deformation of the surrounding rock.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This study analyzes the large deformation failure mode and mechanical mechanism of tunnel surrounding rock, with an aim to lessen the damage of high ground stress soft rock tunnel support structure ...and large deformation of surrounding rock in southwest mountainous area, with Yunnan Changning Tunnel as example for analysis, This paper investigates NPR anchor cable stress compensation support for soft rock tunnel.First, we analyzed the geological conditions and causes of failure of the tunnel through field survey and indoor test.Then, we looked at the main control factors affecting the stability of surrounding rock and the failure mode of surrounding rock of Changning Tunnel.Next, this study proposed the stress compensation support technology with NPR anchor cable as the core.Finally, we analyzed the control effect of surrounding rock of Changning Tunnel under the condition of NPR anchor mesh coupling support through field test.Results show that the main failure modes of the surrounding rock of Changning Tunnel are the compression bending of rock strata and the shear slip between layers.The stress compensation support technology with NPR anchor cable as the core works to effectively control the large deformation of the tunnel surrounding rock in the initial support.The maximum deformation of the tunnel surrounding rock is controlled from 2 150 mm to less than 100 mm, which demonstrates significant control effect.The research results can provide reference for the prevention and control of large deformation of soft rock tunnel.
A physical model for the footwall slope of Nanfen open-pit mine, China was established using a self-developed deep geological engineering disaster model test system. A thermosensitive similar ...material, paraffin, was selected to simulate a weak structural plane in the slope to reproduce the landslide process. From an experimental perspective, the variation trend of shear strength parameters of weak structural plane and the mechanical support characteristics of NPR (negative Poisson’s ratio) anchor cable under the condition of a large landslide deformation and failure were examined. The results of this model test showed that slope failure has four distinct stages: (1) soil compaction stage, (2) crack generation stage, (3) crack propagation stage, and (4) sliding plane transfixion stage. According to the test results, the rock mechanics parameters of weak surface in the footwall slope of Nanfen open-pit mine were calculated. The cohesion is approximately 1.35 × 105 Pa, and the internal friction angle is approximately 6.33°. During slope failure, the NPR anchor cable experiences a large deformation but no damage occurs, indicating that the NPR anchor cable can be continuously monitored and reinforced during the deformation and failure of landslide. The stress characteristics of NPR anchor cables during the test are consistent with the monitoring results of Newtonian force at the landslide site, proving that NPR anchor cables are effective and reasonable in landslide monitoring and early warning.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Derived the mathematical expression of the bending anchor cable.•The bigger curvature corresponds to the smaller rock deformation and larger pull-out force.•Anchor cables with 00-0.50 curvature have ...better reinforcement effect by improving the wall stress.•Anchor cables with larger curvature cause the effective length decrease and uneven stress.
Anchors have been widely used in slope engineering, mining engineering and foundation pit engineering, but their stabilities are significantly affected by anchor cable bending which could be contributed by complicated geological conditions and technical limitations. Theoretical analysis in this paper leads to the establishment of the stress model for the bending anchor cable, and the mathematical expression of the relationship between the ultimate pull-out force and the curvature of the bending anchor cable. Numerical simulation is used to evaluate the effect of the anchor cable curvature on the reinforcement effect. The results suggest that the stress distribution and reinforcement effect are affected by different curvatures, the bigger curvature corresponds to the smaller deformation and the larger pull-out force. The rate of decrease in the anchor cable displacement with the burial depth is linearly related to the pull-out force. In addition, the anchor cable curvature affects the response of the surrounding rock mass to stress and strain: The greater the curvature, the larger the area of the responsive rock mass and the higher mobilization of the strength of the rock mass itself. The anchor cable curvature also influences the reinforcement effect of multiple anchor cables. The results are applied to foundation pit engineering, and it is found as follows: The appropriately bending anchor cable (00-0.50 of curvature) with the same length can make wall stress and deformation more reasonable, and better control foundation deformation; however, with the increase in curvature, the effective anchoring length and the anchor cable depth decrease, and the reinforcement effect declines. The study results can provide reference for anchorage engineering.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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