scholarly journals Analysis of in-situ rock joint strength using digital borehole scanner images

1994 ◽  
Author(s):  
Bhaskar Bahadur Thapa
Keyword(s):  
Joint Strength ◽  
Rock Joint

Seismic Performance on Reinforced Concrete Frame Joints of Open Set Corner Floor

2012 ◽  
Vol 594-597 ◽  
pp. 1766-1770
Author(s):  
Hai Bin Chen ◽  
Nan Ge ◽  
Yan Pu Zhang
Keyword(s):  
Reinforced Concrete ◽  
Joint Strength ◽  
Plastic Hinge ◽  
Time Interval ◽  
Reinforced Concrete Frame ◽  
Concrete Frame ◽  
Finite Element Software ◽  
Open Set ◽  
Calculation Results

Quasi-static analysis of in-situ reinforced concrete frame joints is done by using finite element software ADINA. The calculation results of the ordinary beam-column joints and the surrounding floor located Corner joints are compared. It is shown that near the beam ribbed slab reinforcement stress significantly increases with the loading displacement increasing, indicating that the floor enhance the flexural capacity of beam. On the conditions of no influence the joint strength, floor set corner can be partially weakened the capacity of the beam flexural, and reinforcement of beams yield significantly in advance. When the beam reinforcement yield, the column of concrete cracks have also been reduced. Meanwhile, the beam-end and column-end plastic hinge appears increase the time interval, so that the joints are closer to the characteristics of the beam hinge mechanisms by the earthquake damage.

Identification a of shear mechanism in moderately overburied chemical explosive experiments and relation to the DPRK declared nuclear tests

2020 ◽  
Author(s):  
David Steedman ◽  
Christopher Bradley
Keyword(s):  
Body Wave ◽  
Source Region ◽  
Rock Joint ◽  
In Situ Stress ◽  
Explosive Loading ◽  
Nuclear Tests ◽  
Ground Shock ◽  
Spherical Shock ◽  
Shear Energy

<p>The Source Physics Experiments (SPE) provided new insights into explosion phenomenology. In particular, the data reveal a mechanism for generating shear energy in the near-source region which may explain why certain North Korean declared nuclear tests do not conform to explosion/earthquake discriminants based on relative body wave (m<sub>b</sub>) and shear wave (M<sub>S</sub>) magnitudes.</p><p>The SPE chemical explosive detonations in granite included three scaled depth of burial (SDOB) categories: 1) nominally buried defines the burial depths from which m<sub>b</sub>:M<sub>S</sub> discriminants were derived; 2) deeply overburied, or Green’s function depth; and 3) moderately overburied, or between the two end cases above. This last category is a general descriptor for the North Korean declared nuclear tests which fail the m<sub>b</sub>:M<sub>S</sub> discriminant.</p><p>Near-source three-axis borehole accelerometers indicate that the nominal and deeply buried SPE experiments created the expected spherical shock environment dominated by radial ground motion with insignificant tangential response.</p><p>The moderately overburied SPE experiments indicate a significant contrast. The tangential records in these experiments are quiescent with initial shock arrival and then exhibit a sudden, significant surge immediately following the peak radial component. At distant ranges where the shock wave amplitude has attenuated the environment becomes more consistent with a spherical shock with no significant tangential components.</p><p>We interpret a “shear release” mechanism on an obliquely loaded rock joint:</p><ol><li>During incipient loading the normal shock component forces closure of the joint.</li> <li>In cases of low explosive loading and/or high in situ stress the tangential component is insufficient to cause joint sliding and this load is stored as shearing strain.</li> <li>As the ground shock peak passes the joint unloads and dilates, and the now open joint allows a sudden release of the stored shear strain resulting in sudden joint rupture and slippage.</li> </ol><p>Step 3 above is essential for identifying when this mechanism occurs. For large in situ stress accompanied by low explosive loading (i.e., deep burial, or high SDOB) the joint fails to open and rupture does not occur. For low in situ stress accompanied by high explosive loading (i.e., shallow burial, or nominal SDOB) there is insufficient resistance to tangential slippage and no shear energy is stored for later release.</p><p>The above provides a fully geodynamic definition for why certain explosive events in jointed rock will fall within the correct explosion population of a m<sub>b</sub>:M<sub>S</sub> discriminant while others may not. Moreover, we illustrate that these observations for the SPE results map directly to generally accepted yield and depth combinations for the six declared North Korean nuclear tests.</p>

Effect of In Situ Post Weld Heat Treatment on Mechanical Behavior and Austenite–Ferrite Phase Balance of Fe-Cr-Ni/Fe-Cr Stainless Steels Upset Resistance Dissimilar Weld

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Ashkaan Ozlati ◽  
Mojtaba Movahedi
Keyword(s):  
Heat Treatment ◽  
Optimum Condition ◽  
Grain Growth ◽  
Stainless Steels ◽  
Joint Strength ◽  
High Strength ◽  
Post Weld Heat Treatment ◽  
Dissimilar Weld ◽  
Phase Balance

Abstract Effect of the in situ post weld heat treatment (PWHT) was investigated on the flash profile, austenite/ferrite phase balance, and mechanical properties of the upset resistance dissimilar weld between Fe-Cr-Ni and Fe-Cr stainless steels rods. In order to explore the effect of the heat treatment on the joint strength, two as-welded samples with low strength (116 MPa) and high strength (372 MPa) were used. The results showed that in situ PWHT was beneficial for both welded samples, though in different ways. For the weld with low strength, PWHT improved the joint strength (∼130% increase in the optimum condition compared with the as-welded sample) due to the increase in the size of the flash and the related bonded area at the joint interface. However, ferrite percent in the weld zone increased from ∼50% up to ∼70%. For the sample with the high strength, ferrite/austenite phase balance was restored at an optimum condition of PWHT. However, the joint strength decreased slightly (less than 5%) due to the grain growth in the Fe-Cr rod, i.e., the fracture location. Fracture analysis was used for justification of the variations in the joint strength. For both Fe-Cr-Ni side and Fe-Cr side of the welds, in situ PWHT generally reduced the hardness. This observation is discussed in light of the simultaneous effects of the grain growth and formation of little martensite.

scholarly journals Prediction of Stope Stability Using Variable Weight and Unascertained Measurement Technique

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Qian Kang ◽  
Yunmin Wang ◽  
Shuwen Zhang ◽  
Chengzhi Pu ◽  
Chuxuan Zhang
Keyword(s):  
Rock Joint ◽  
Evaluation Index System ◽  
Groundwater Seepage ◽  
Rock Quality ◽  
Variable Weight ◽  
Risk Grade ◽  
Strength Rock ◽  
Index Weight ◽  
Measure Evaluation

A new model is established to analyze mining stope stability, using variable weight theory to calculate the index weight for each factor in different stopes and unascertained measure evaluation technique to predict the risk grade of stope stability. In this model, an evaluation index system by virtue of the 7 most important factors is established, including rock saturated uniaxial compressive strength, rock quality designation, rock joint and fissure, stope span, condition of pillar, groundwater seepage volume, and rate of supporting pit roof. And each index is divided into 5 grades by assignment value and the classification method of standardization. Accordingly, the analysis result is also classified into 5 risk grades. This model is used for the 6 main stopes from the -270 m section in Xin-Qiao Mine, China. The results, giving risk grade for each stope and guiding the use of corresponding measures, avoided the problem of state out of balance caused by conventional invariable weight theory models and have ensured no accident occurred in mining production in recent years. This model can be used in other mines widely, by assigning values for the 7 factors on basis of current in situ cases.

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