The core-disk phenomenon has been observed generally in the drilling process under high-stress conditions.This paper presents the in-situ experimental study of the coring-disking failure mechanism of marble in an unde...The core-disk phenomenon has been observed generally in the drilling process under high-stress conditions.This paper presents the in-situ experimental study of the coring-disking failure mechanism of marble in an underground cavens with 2400 m depth.Based on the disk samples in several boreholes with different diameters,both macro-and micro-morphological characteristics of core-disks’break surface were analysis,using 3D optical scanning and electron microscope scanning.Moreover,the numerical back analysis was also used to simulate the drilling process for demonstrating the development of core disking.The in-situ experiment results showed that the failure types of core disking consisted of tensile break and shear break,i.e.,the shear break usually appears in the edge part of break surface,and tensile break appears in the central part.What’s more,the ration of core-disks thickness to borehole diameter is in a relatively stable range.Numerical back analysis indicated this micro asynchronous break of hard marble is induced by high geostress and unloading drill.展开更多
The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of i...The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of individual wires and completely wound PC-strand cables. PC-strand cables with smooth wires and the recent anchorage enhancement innovation of indentation were evaluated and compared. The testing protocol detailed in ISO Standard 15630 utilizes a mandrel system that was investigated at 3different diameters which alters the wire to mandrel ratio from 2:1 to 9:1. The results demonstrate that the difference between smooth and indented wires is statistically insignificant when larger diameter mandrels are used,and that indentation does not adversely affect strand properties and performance.Insight into the shearing mechanism and evaluation techniques are discussed with the introduction of triaxial loading to describe the PC-strand tensile and shearing mechanisms. Another important result indicates that the shear strength of PC-strand cable bolting systems has a greater shear strength value than traditional steel bar bolting systems.展开更多
The important parameters that influence the mechanical property of the pavinglayer on an orthotropic steel bridge deck are the paving layer thickness and modulus of the asphaltconcrete surfacing. Three important indic...The important parameters that influence the mechanical property of the pavinglayer on an orthotropic steel bridge deck are the paving layer thickness and modulus of the asphaltconcrete surfacing. Three important indices that control the typical failures of the paving layerare the maximum tensile stress of paving layer, the maximum shear stress between the steel deck andthe paving layer, and the maximum deflection on the paving surface. In this paper, the analyticalmodel of paving systems on orthotropic steel bridge deck is established, and the finite elementmethod is adopted to study the stress and strain of paving system. With the variation of asphaltconcrete modulus in high or low temperature season, the influences of paving layer thickness onthree control indices are researched. The results provide a theoretical basis for the determinationof thickness of the paving layer on the steel bridge deck.展开更多
基金Projects(U1965205,51779251,41672314)supported by the National Natural Science Foundation of China。
文摘The core-disk phenomenon has been observed generally in the drilling process under high-stress conditions.This paper presents the in-situ experimental study of the coring-disking failure mechanism of marble in an underground cavens with 2400 m depth.Based on the disk samples in several boreholes with different diameters,both macro-and micro-morphological characteristics of core-disks’break surface were analysis,using 3D optical scanning and electron microscope scanning.Moreover,the numerical back analysis was also used to simulate the drilling process for demonstrating the development of core disking.The in-situ experiment results showed that the failure types of core disking consisted of tensile break and shear break,i.e.,the shear break usually appears in the edge part of break surface,and tensile break appears in the central part.What’s more,the ration of core-disks thickness to borehole diameter is in a relatively stable range.Numerical back analysis indicated this micro asynchronous break of hard marble is induced by high geostress and unloading drill.
文摘The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of individual wires and completely wound PC-strand cables. PC-strand cables with smooth wires and the recent anchorage enhancement innovation of indentation were evaluated and compared. The testing protocol detailed in ISO Standard 15630 utilizes a mandrel system that was investigated at 3different diameters which alters the wire to mandrel ratio from 2:1 to 9:1. The results demonstrate that the difference between smooth and indented wires is statistically insignificant when larger diameter mandrels are used,and that indentation does not adversely affect strand properties and performance.Insight into the shearing mechanism and evaluation techniques are discussed with the introduction of triaxial loading to describe the PC-strand tensile and shearing mechanisms. Another important result indicates that the shear strength of PC-strand cable bolting systems has a greater shear strength value than traditional steel bar bolting systems.
文摘The important parameters that influence the mechanical property of the pavinglayer on an orthotropic steel bridge deck are the paving layer thickness and modulus of the asphaltconcrete surfacing. Three important indices that control the typical failures of the paving layerare the maximum tensile stress of paving layer, the maximum shear stress between the steel deck andthe paving layer, and the maximum deflection on the paving surface. In this paper, the analyticalmodel of paving systems on orthotropic steel bridge deck is established, and the finite elementmethod is adopted to study the stress and strain of paving system. With the variation of asphaltconcrete modulus in high or low temperature season, the influences of paving layer thickness onthree control indices are researched. The results provide a theoretical basis for the determinationof thickness of the paving layer on the steel bridge deck.
