Mechanical behavior of 2G NPR bolt anchored rock samples under static disturbance loading

The deep mining of coal resources is accompanied by severe environmental challenges and various potential engineering hazards.The implementation of NPR(negative Poisson's ratio)bolts are capable of controlling large deformations in the surrounding rock effectively.This paper focuses on studying the mechanical properties of the NPR bolt under static disturbance load.The deep nonlinear mechanical experimental system was used to study the mechanical behavior of rock samples with different anchored types(unanchored/PR anchored/2G NPR anchored)under static disturbance load.The whole process of rock samples was taken by high-speed camera to obtain the real-time failure characteristics under static disturbance load.At the same time,the acoustic emission signal was collected to obtain the key characteristic parameters of acoustic emission such as acoustic emission count,energy,and frequency.The deformation at the failure of the samples was calculated and analyzed by digital speckle software.The findings indicate that the failure mode of rock is influenced by different types of anchoring.The peak failure strength of 2G NPR bolt anchored rock samples exhibits an increase of 6.5%when compared to the unanchored rock samples.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 62.16%and 62.90%,respectively.The maximum deformation of bearing capacity exhibits an increase of 59.27%,while the failure time demonstrates a delay of 42.86%.The peak failure strength of the 2G NPR bolt anchored ones under static disturbance load exhibits an increase of 5.94%when compared to the rock anchored by PR(Poisson's ratio)bolt.The cumulative count and cumulative energy of acoustic emission exhibit a decrease of 47.16%and 43.86%,respectively.The maximum deformation of the bearing capacity exhibits an increase of 50.43%,and the failure time demonstrates a delay of 32%.After anchoring by 2G NPR bolt,anchoring support effectively reduces the risk of damage caused by static disturbance load.These results demonstrate that the support effect of 2G NPR bolt materials surpasses that of PR bolt.

Strength characteristics of rock anchored by NPR bolt with different preloads

This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.

Separation Properties of a New Polysiloxane-Anchored β-Cyclodextrin Derivative as Gas Chromatography Stationary Phase

A new capillary gas chromatography stationary phase, monokis (2,6 di O benzyl 3 O propyl (3’)) hexakis(2,6 di O benzyl 3 O methyl) β CD bonded polysiloxane, was synthesized. It exhibited separation abilities to disubstituted benzene isomers and some chiral solutes. It was also found that the polarity of CD derivatives can be lowered both by chemically bonding it to polysiloxane and by diluting it in polysiloxane. The separation abilities of the polysiloxane anchored CDs (SP CD) are higher than that of the unbonded CDs (S CD) and the diluted S CD at lower column temperature. Hydrosilylation reaction is one of the best methods to lower the operating temperature of CDs.

Miniature magnetically anchored and controlled camera system for trocar-less laparoscopy

AIM To design a miniature magnetically anchored and controlled camera system to reduce the number of trocars which are required for laparoscopy.METHODS The system consists of a miniature magnetically anchored camera with a 30° downward angle, an external magnetically anchored unit, and a vision output device. The camera weighs 12 g, measures Φ10.5 mm × 55 mm and has two magnets, a vision model, a light source, and a metal hexagonal nut. To test the prototype, the camera was inserted through a 12-mm conventional trocar in an ex vivo real liver laparoscopic training system. A trocar-less laparoscopic cholecystectomy was performed 6 times using a 12-mm and a 5-mm conventional trocar. In addition, the same procedure was performed in four canine models.RESULTS Both procedures were successfully performed using only two conventional laparoscopic trocars. The cholecystectomy was completed without any major complication in 42 min(38-45 min) in vitro and in 50 min(45-53 min) using an animal model. This camera was anchored and controlled by an external unit magnetically anchored on the abdominal wall. The camera could generate excellent image. with no instrument collisions.CONCLUSION The camera system we designed provides excellent optics and can be easily maneuvered. The number of conventional trocars is reduced without adding technical difficulties.

Color constancy using color edge moments and regularized regression in anchored neighborhood

To improve the accuracy of illumination estimation while maintaining a relative fast execution speed, a novel learning-based color constancy using color edge moments and regularized regression in an anchored neighborhood is proposed. First, scene images are represented by the color edge moments of various orders. Then, an iterative regression with a squared Frobenius norm（F-norm） regularizer is introduced to learn the mapping between the edge moments and illuminants in the neighborhood of the anchored sample.Illumination estimation for the test image finally becomes the nearest anchored point search followed by a matrix multiplication using the associated mapping matrix which can be precalculated and stored. Experiments on two standard image datasets show that the proposed approach significantly outperforms the state-of-the-art algorithms with a performance increase of at least 10. 35% and 7. 44% with regard to median angular error.

Co-Evolution Optimization of Anchored Row Piles for Deep Foundation Pit

The thinking of co evolution is applied to the optimization of retaining and protecting structure for deep foundation excavation, and the system of optimization of anchored row piles for deep foundation pit has been already developed successfully. For the co evolution algorithm providing an evolutionary mechanism to simulate ever changing problem space, it is an optimization algorithm that has high performance, especially applying to the optimization of complicated system of retaining and protecting for deep foundation pit. It is shown by many engineering practices that the co evolution algorithm has obvious optimization effect, so it can be an important method of optimization of retaining and protecting for deep foundation pit. Here the authors discuss the co evolution model, object function, all kinds of constraint conditions and their disposal methods, and several key techniques of system realization.

TRANSFER HYDROGENATION OF KETONES BY PROPAN－2－OL OVER POLY（PHENYLENE OXIDE） ANCHORED RUTBENIUM CATALYST

Both aliphatic and aromatic ketones are efficiently transfer-hydrogenated by propan-2-ol under mild conditions in the presence of a catalytic amount of poly(2,6-dimethyl-1,4-Phenylene oxide) (PPO) anchored ruthenium complex and sodium hydroxide. An important feature of this polymer anchored catalyst is its stability in air.

Atomically dispersed Fe atoms anchored on N-doped carbon hollow nanospheres boost the electrocatalytic performance for oxygen reduction reaction

Oxygen reduction reaction(ORR)is the key reaction at the cathode of proton exchange membrane fuel cells(PEMFCs)and metal-air batteries(1)To address the challenges associated with Pt-based electrocatalysts having prominent activity for ORR,e.g.scarce abundance,prohibitive cost,poor stability,and vulnerability to reaction intermediates,it is necessary to explore other cost-effective ORR electrocatalysts with competitive or even superior performance to promote the commercialization of the energy conversion devices.

CARBONYLATION OF ALLYL HALIDES CATALYZED BY POLY(N-VINYL-2-PYRROLIDONE) ANCHORED PALLADIUM CATALYST UNDER ATMOSPHERIC PRESSURE

Carbonylation of allyl halides catalyzed by poly(N-vinyl-2-pyrro- lidone) anchored palladium catalyst affords β,r-butonic acid under atmo- spheric pressure and at room temperature.The activity and efficiency of the catalyst are much higher than those of the reported catalysts for this reaction.

Simulation experiment on anti-penetration capability of anchored rock mass

In order to solve the problem of experimental research on the penetration process of projectile into anchored rock mass, we derived the essential similarity conditions for the physical simulation experi- ment according to the similarity theory, carried out the experiment on the penetration process of a kind of penetrating bomb into the anchored rock mass of type III, and compared the experimental results with the values computed by the professional Young's empirical formula. The test results show that the phys- ical simulation experiment can represent the actual penetration process of projectile into anchored rock mass. The research method proposed in this paper provides technical support for the experimental research on the design and reconstruction of underground protection works.

Design Concept for an Anchored Diaphragm Wall in the Central Part of Budva, Montenegro

This paper presents a design concept and acceptance test application procedure for a deep pit protection structure. The structure is intended for use in the construction of three underground levels of a residential building： A, B, C and D, located in Block 10C, Budva, Montenegro. The anchored wall will consist of non-gravity cantilevered walls with three levels of ground anchors. Non-gravity cantilevered walls employ continuous walls constructed in slurry trenches （i.e., slurry （diaphragm） walls）, e.g., vertical elements that are drilled to depths below the finished excavation grade. For those non-gravity cantilevered walls, support is provided through the shear and bending stiffness of the vertical wall elements and passive resistance from the soil below the finished excavation grade. Anchored wall support relies on these components as well as lateral resistance provided by the ground anchors to resist horizontal pressures （e.g., earth, water and external loads） acting on the wall. The anchored wall analyzed in this paper will be recommended for use as a temporary supporting structure necessary for the excavation and erection of the underground structure. The design life of the temporary ground anchors is two years. Dynamic loads are not considered in this analysis.

Graphdiyne scaffold anchored highly dispersed ruthenium nanoparticles as an efficient cathode catalyst for rechargeable Li-CO_(2) battery

Lithium (Li)-CO_(2) battery is rising as an attractive energy-storage system with the competence of CO_(2) conversion/fixation. However, its practical development is seriously hindered by the high overpotential. Herein, a rational design on a highly catalytic Li-CO_(2) battery electrode built by graphdiyne powder as a multi-functional laminar scaffold with anchored highly dispersed Ru nanoparticles is explored. The strong interaction between the abundant acetylenic bond sites of graphdiyne scaffold and Ru nanoparticles can effectively promote the electrochemical progress and reduce the voltage polarization. The unique channels architecture of the cathodic catalyst with enough space not only accelerates CO_(2) diffusion and electrons/Li+ transport, but also allows a large amount of accommodation for discharged product (Li2CO3) to assure an advanced capacity. The corresponding Li-CO_(2) battery displays an advanced discharged capacity of 15,030 mAh/g at 500 mA/g, great capacity retention of 8873 mAh/g at 2 A/g, high coulombic efficiency of 97.6% at 500 mA/g and superior life span for 120 cycles with voltage gap of 1.67 V under a restricted capacity of 1000 mAh/g at 500 mA/g. Ex/in-situ studies prove that synergy between Ru nanoparticles and acetylene bonds of GDY can boost the round-trip CO_(2)RR and CO_(2)ER kinetics.

Shear behaviour of anchored jointed rock mass under different engineering conditions considering damage and joint surface morphology

According to different geological conditions and engineering disturbance,three dimensional numerical models of anchored jointed rock mass with two kinds of boundary conditions of constant normal load(CNL)and constant normal stiffness(CNS)were constructed considering the ductility damage of rockbolt,the stiffness degradation of grouting layer and the joint surface roughness.The effects of anchorage angle,joint surface morphology,and boundary conditions on the shear performance of anchorage system were analyzed,and the failure characteristics under different working conditions were revealed.Finally,the analytical solution of shear strength of anchored system was established.Results show that the larger the anchorage angle is,the more serious the necking phenomenon of rockbolt will be.The damage degree of the bonding layer and the horizontal displacement of the bedding rock mass decrease with the increase of the joint surface roughness.The CNL condition is to instantaneously apply high normal stress,and the CNS condition is to gradually form a high normal stress environment through the superposition of increment on the basis of the initial value,which can resist greater transverse load.This is equivalent to enhancing the ductility of the rockbolt.The shear strength of the system increases with the increase of normal stress and normal stiffness.Ignoring the normal stiffness will underestimate the shear strength.

Monotonic uplift behavior of anchored pier foundations in soil overlying rock

Rock-embedded foundations with good uplift and bearing capacity are often used in mountains or hilly areas.However,there are soil layers with a certain thickness on the rocks in these mountainous areas,and the utilization of those soil layers is a problem worthy of attention in foundation construction.Considering construction-and cost-related factors,traditional single-form foundations built on such sites often cannot provide sufficient resistance against uplift.Therefore,an anchored pier foundation composed of anchors and belled piers,specifically constructed for such conditions,can be invaluable in practice.This paper introduces an experimental and analytical study to investigate the uplift capacity and the uplift mobilization coefficients(UMCs)of the anchored pier foundation.In this study,three in-situ monotonic pullout tests were carried out to analyze the load–displacement characteristics,axial force distribution,load transfer mechanism,and failure mechanism.A hyperbolic model is used to fit the load–displacement curves and to reveal the asynchrony of the ultimate limit states(ULSs)of the anchor group and the belled pier.Based on the results,the uplift capacity can be calculated by the UMCs and the anchor group and pier uplift capacities.Finally,combined with the estimation of the deformation modulus of the soil and rock,the verification calculation of the uplift capacity and UMC was carried out on the test results from different anchored pier foundations.

Magnetically accelerated thermal energy storage within Fe_(3)O_(4)-anchored MXene-based phase change materials

Inherent weak photon-capturing ability is a long-standing bottleneck for pristine phase change materials(PCMs)in photothermal conversion application.To conquer this difficulty,herein,magnetic Fe_(3)O_(4) nanoparticles were in situ anchored between the layers and the surface of two-dimensional MXene for the infiltration of myristic acid(MA)by an in situ chemical anchoring strategy.Benefiting from the synergistic localized surface plasmon resonance effect of MXene and Fe_(3)O_(4) nanoparticles,our designed MXene@Fe_(3)O_(4)-MA composite PCMs harvested an ultrahigh photothermal conversion efficiency of 97.7%.During the photothermal conversion process,MXene can capture photons and convert solar energy into heat energy efficiently,and the in situ anchored Fe_(3)O_(4) nanoparticles further enhanced the photothermal conversion efficiency.Moreover,the introduction of Fe_(3)O_(4) nanoparticles improved the thermal energy storage density(144.17 J/g)of MXene-MA composite PCMs since Fe_(3)O_(4) nanoparticles provided more heterogeneous nucleation sites for MA.Simultaneously,MXene@Fe_(3)O_(4)-MA composite PCMs were endowed with excellent paramagnetism,and realized efficient magnetic-thermal conversion.Additionally,MXene@Fe_(3)O_(4)-MA composite PCMs exhibited excellent energy conversion stability,thermal stability,and reliability after undergoing multiple thermal cycles.Therefore,high-performance MXene@Fe_(3)O_(4)-based energy conversion composite PCMs are promising candidates to accelerate efficient utilization of the practical solar energy and magnetic energy.

Energy mechanism of bolt supporting effect to fissured rock under static and dynamic loads in deep coal mines

The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.

Mechanical responses of anchoring structure under triaxial cyclic loading

Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the investigation of the mechanical response,failure mode,instability assessment criteria,and anchorage effect of AS subjected to combined cyclic dynamic-static triaxial stress paths.The results show that the peak bearing strength is positively correlated with the anchoring matrix strength,anchorage length,and edgewise compressive strength.The bearing capacity decreases significantly when the anchorage direction is severely inclined.The free face failure modes are typically transverse cracking,concave fracturing,V-shaped slipping and detachment,and spallation detachment.Besides,when the anchoring matrix strength and the anchorage length decrease while the edgewise compressive strength,loading rate,and anchorage inclination angle increase,the failure intensity rises.Instability is determined by a negative tangent modulus of the displacement-strength curve or the continued deformation increase against the general downward trend.Under cyclic loads,the driving force that breaks the rock mass along the normal vector and the rigidity of the AS are the two factors that determine roadway stability.Finally,a control measure for surrounding rock stability is proposed to reduce the internal driving force via a pressure relief method and improve the rigidity of the AS by full-length anchorage and grouting modification.

Instability mechanism of mining roadway passing through fault at different angles in kilometre-deep mine and control measures of roof cutting and NPR cables

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable"(PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°-30°, α of type II being 30°-60°, and α of type III being 60°-90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3-7 times, and the cumulative convergence was reduced by 45%-50%. It provides a reference for the stability control of the deep fault-through mining roadway.

Mechanism of high-preload support based on the NPR anchor cable in layered soft rock tunnels

The control of large deformation problems in layered soft rock tunnels needs to solve urgently.The roof problem is particularly severe among the deformation issues in tunnels.This study first analyzes the asymmetric deformation modes in layered soft rock tunnels with large deformations.Subsequently,we construct a mechanical model under ideal conditions for controlling the roof of layered soft rock tunnels through high preload with the support of NPR anchor cables.The prominent roles of long and short NPR anchor cables in the support system are also analyzed.The results indicate the significance of high preload in controlling the roof of layered soft rock tunnels.The short NPR anchor cables effectively improve the integrity of the stratified soft rock layers,while the long NPR anchor cables effectively mobilize the self-bearing capacity of deep-stable rock layers.Finally,the high-preload support method with NPR anchor cables is validated to have a good effect on controlling large deformations in layered soft rock tunnels through field monitoring data.

Seabed structures and foundations related to deep-sea resource development:A review based on design and research

The deep‐sea ground contains a huge amount of energy and mineral resources,for example,oil,gas,and minerals.Various infrastructures such as floating structures,seabed structures,and foundations have been developed to exploit these resources.The seabed structures and foundations can be mainly classified into three types:subsea production structures,offshore pipelines,and anchors.This study reviewed the development,installation,and operation of these infrastructures,including their structures,design,installation,marine environment loads,and applications.On this basis,the research gaps and further research directions were explored through this literature review.First,different floating structures were briefly analyzed and reviewed to introduce the design requirements of the seabed structures and foundations.Second,the subsea production structures,including subsea manifolds and their foundations,were reviewed and discussed.Third,the basic characteristics and design methods of deep‐sea pipelines,including subsea pipelines and risers,were analyzed and reviewed.Finally,the installation and bearing capacity of deep‐sea subsea anchors and seabed trench influence on the anchor were reviewed.Through the review,it was found that marine environment conditions are the key inputs for any offshore structure design.The fabrication,installation,and operation of infrastructures should carefully consider the marine loads and geological conditions.Different structures have their own mechanical problems.The fatigue and stability of pipelines mainly depend on the soil‐structure interaction.Anchor selection should consider soil types and possible trench formation.These focuses and research gaps can provide a helpful guide on further research,installation,and operation of deep‐sea structures and foundations.