External blast load factors for dome structures based on reliability

Dome structures have been used extensively for industrial,residential,and military infrastructure.Therefore,it is necessary to understand the damage risk potential for such structures for blast-resistant design considerations.This paper investigates the effect of blast load variability on the design value and the structural dynamic response.Therefore,the sources of uncertainty in the external blast load on dome structures were discussed firstly.Then based on the probabilistic blast load model for the dome,the rationality of a deterministic mass-increase safety method was assessed.It was found that previous deterministic design method cannot provide a consistent and sound assurance factor or reliability index on the entire dome roof.In addition,it was also proved that the assurance-based load method fails to ensure compliance with structural safety design standards on the dome roof when compared with the reliability-based blast method.A sensitivity analysis on the probabilistic blast load was conducted,and the results indicate that stand-off distance and explosive mass both act as dominant sources to influence the mean and variability of blast load.Therefore,based on the Latin hypercube sampling method,a reliability-based external blast load factor technique was proposed.This technique was further used to estimate structural damage levels of a single-layer reticulated dome under different reliability requirements,associated with a low,medium,and high level of protection grades for a specific explosion scenario,and it indicated that this technique can be useful in the building design to achieve a higher structural anti-explosion capacity.This study herein can serve as a reference for the calculation method of designed blast load.

Measurement-while-drilling technique and its scope in design and prediction of rock blasting

With rampant growth and improvements in drilling technology, drilling of blast holes should no longer be viewed as an arduous sub-process in any mining or excavation process. Instead, it must be viewed as an important opportunity to quickly and accurately measure the geo-mechanical features of the rock mass on-site, much in advance of the downstream operations. It is well established that even the slightest variation in lithology, ground conditions, blast designs vis-a-vis geologic features and explosives performance, results in drastic changes in fragmentation results. Keeping in mind the importance of state-of-the-art measurement-while-drilling （MWD） technique, the current paper focuses on integrating this technique with the blasting operation in order to enhance the blasting designs and results. The paper presents a preliminary understanding of various blasting models, blastability and other related concepts, to review the state-of-the-art advancements and researches done in this area. In light of this, the paper highlights the future needs and implications on drill monitoring systems for improved information to enhnnrp th~ hl^tin~ r^HIt~

New Blast Damage Criterion for Damage Prediction

There are several underground mines in India which operate in close proximity to an operating surface mine.Under such scenario,the blast induced stress waves generated due to surface blasting may be a potential source to cause instability of adjoining underground mine structures.Using seismographs,54 blast induced vibration data were recorded at various locations in the roof,floor and pillars of the underground mine at Hingir Rampur mine of Coal India Limited by synchronizing the timing of surface blasting carried at an adjacent Samleshwari opencast mine.Results of this study show that Artificial Neural Network(ANN)has better prediction potential of peak particle velocity(PPV)and damage to adjacent underground structures due to surface blasting as compared to conventional regression methods.In order to assess and predict the impact of surface blasts on underground workings,Blast Damage Factor(BDF)has been evolved.The study shows that site specific charts can predict the blast damage class at an underground location due to surface blasting for known distances and explosive charge per delay.The severe damage in case study mine site took place when peak particle velocity exceeded 162 mm/s and PPV less than 51 mm/s had no probability of damage to underground structures due to surface blasting.