Development of multi-functional anchorage support dynamic-static coupling performance test system and its application

In underground engineering with complex conditions,the bolt(cable)anchorage support system is in an environment where static and dynamic stresses coexist,under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress.It is essential to study the support components performance under dynamic-static coupling conditions.Based on this,a multi-functional anchorage support dynamic-static coupling performance test system(MAC system)is developed,which can achieve 7 types of testing functions,including single component performance,anchored net performance,anchored rock performance and so on.The bolt and cable mechanical tests are conducted by MAC system under different prestress levels.The results showed that compared to the non-prestress condition,the impact resistance performance of prestressed bolts(cables)is significantly reduced.In the prestress range of 50–160 k N,the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5%compared to non-prestress condition.In the prestress range of 150–300 k N,the impact energy resisted by high-strength cable is reduced by76.8%–84.6%compared to non-prestress condition.The MAC system achieves dynamic-static coupling performance test,which provide an effective means for the design of anchorage support system.

Adjustment mechanism of blasting dynamic-static action in the water decoupling charge

Water decoupling charge blasting excels in rock breaking,relying on its uniform pressure transmission and low energy dissipation.The water decoupling coefficients can adjust the contributions of the stress wave and quasi-static pressure.However,the quantitative relationship between the two contributions is unclear,and it is difficult to provide reasonable theoretical support for the design of water decoupling blasting.In this study,a theoretical model of blasting fracturing partitioning is established.The mechanical mechanism and determination method of the optimal decoupling coefficient are obtained.The reliability is verified through model experiments and a field test.The results show that with the increasing of decoupling coefficient,the rock breaking ability of blasting dynamic action decreases,while quasi-static action increases and then decreases.The ability of quasi-static action to wedge into cracks changes due to the spatial adjustment of the blast hole and crushed zone.The quasi-static action plays a leading role in the fracturing range,determining an optimal decoupling coefficient.The optimal water decoupling coefficient is not a fixed value,which can be obtained by the proposed theoretical model.Compared with the theoretical results,the maximum error in the model experiment results is 8.03%,and the error in the field test result is 3.04%.

Dynamic-static coupled sensing of trace biomarkers by molecularly imprinted metal-organic frameworks

Accommodating target analytes within the pores of metal-organic frameworks(MOFs)to improve the sensing performance is an important but challenging task.Here,we report a novel molecular imprinting strategy to create target recognition sites in a tailored multicomponent MOF with the inter-ligand synergistic antenna effect to lanthanide ions,enabling selective recognition of trace biomarkers,which is critical to the early diagnosis of age-related diseases in blood samples with high sensitivity and ultralow limit of detection(LOD)of 69 nmol L^(-1).Compared with MOF-based sensors without imprinted recognition sites,the significantly enhanced sensing performance(both sensitivity and LOD)was attributed to a dynamic-static coupled sensing mechanism:the dynamic interactions involve concentrating the trace biomarkers at the imprinted recognition sites to enhance the sensing performance at ultralow concentration,and the static interactions are derived from electron/energy exchange between the molecularly imprinted MOF and the biomarker to govern the sensing performance.This work establishes a new molecular imprinting strategy to attain advanced materials for sensing trace bio-analytes.

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.

Caustic study on blast-induced wing crack behaviors in dynamic–static superimposed stress field

This paper studies blast-induced wing crack behavior in a dynamic–static superimposed stress field using high-speed photography in combination with the optical method of caustics. With a static–dynamic loading setup, four PMMA plate specimens with pre-existing cracks under different static loading and the same dynamic loading were tested to observe the mechanical characteristics and the kinematic characteristics of blast-induced wing cracks during the propagation process, including crack length, crack velocity and dynamic stress intensity factor(SIF) at the crack tip. The results show that the behavior of the blast-induced wing crack is affected by the explosion stress wave and initial static stress, and the initial static stress with the direction being perpendicular to the wing crack propagation direction hinders crack propagation. Furthermore, the boundary constraint condition of the specimen plays an important role on the behavior of the crack propagation in the experiment.

汉语动态形容词的界说及其基本特征

动态形容词,其与静态形容词词相对,是形容词内部的语义分类,因此划分的标准应是语义的,而非句法(结构)的,按句法(结构)标准划分出来的所谓的动态形容词,其实只是“形容词的动态化”现象,而非真正意义上的“动态形容词”,二者应该区别开来。动态形容词的动性不是来源于形容词的动态化,而是源于自身;静态形容词的动性不是源于自身,而是通过形容词动态化而获得的,二者在语义上有根本差异。动态形容词具有“有意志”性和“内在特征”性,与此相对,静态形容词具有“无意志”性和“外在特征”性。