scholarly journals Numerical Investigation on Influential Factors for Quality of Smooth Blasting in Rock Tunnels

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Baoping Zou ◽  
Zhipeng Xu ◽  
Jianxiu Wang ◽  
Zhanyou Luo ◽  
Lisheng Hu
Keyword(s):  
Rock Mass ◽  
Numerical Investigation ◽  
Detonation Velocity ◽  
Influential Factors ◽  
Site Conditions ◽  
Rock Masses ◽  
Charge Concentration ◽  
Rock Tunnels ◽  
Smooth Blasting

The quality of smooth blasting including the volume of over-/underbreak and blasting-induced damage of surrounding rocks has been extensively considered to be highly correlated to both the cost and advancement rate of rock tunnelling excavated by the drill-blast method. A general control strategy for smooth blasting is too difficult to be available due to the uncertainties and complexity of rock masses, as well as the varying blasting operations. As prerequisite for the evaluation of the blasting quality, effective identification of the influential factors affecting smooth blasting usually plays a significant role in the improvement of smooth blasting design. Compared to the expensive and time-consuming experiments including physical modelling and field tests, numerical modelling, as a cost-efficient approach, offers an attractive alternative to investigate the influential factors in terms of weight, which might be more applicable and reliable for the optimization of smooth blasting parameters. In this case, the dominant factors and secondary factors can be quantitatively identified. Considering the dominant factors often orient the development of things; in this work, a numerical-based approach was proposed to quantitatively identify the dominant factors influencing the quality of smooth blasting. Proposed 3-dimensional blasting modelling was based on LS-DYNA to simulate the occurrence of smooth blasting in rock masses, and the erosion algorithm was also employed to determine the fracturing of jointed rocks. The orthogonal experimental design method was utilized to optimize the experimental arrangement. Seven factors with 4 levels including the perimeter hole spacing, line of least resistance, charge concentration, charging explosive, type of rock mass, detonation velocity, and drilling deviation were taken into account. The geological setting and project background of a real rock tunnel served for the Chengdu-Chongqing high-speed railway were selected as the site conditions to perform the numerical investigation. Calculated area and distance of overbreak as the observed parameters indicating the quality of smooth blasting were utilized to determine sensitivities of factors based on the range analysis of orthogonal experiments. The results suggested that the type of rock mass has the greatest influence on the blasting quality, whereas the charge concentration and detonation velocity can be considered as the secondary factors under the specific site conditions. The proposed numerical approach for assessing influential factors of quality of smooth blasting under specified geological conditions is expected to improve the parameter design and operation of smooth blasting in practical applications.

scholarly journals FIELD EVALUATION OF MINE BLASTING EFFICIENCY

2020 ◽  
Vol 2 (2) ◽  
pp. 1-16
Author(s):  
Piotr Mertuszka ◽  
Marcin Szumny ◽  
Krzysztof Fuławka ◽  
Stanislav Nikolov
Keyword(s):  
Quality Assessment ◽  
Detonation Velocity ◽  
Field Evaluation ◽  
The Other ◽  
Site Conditions ◽  
Site Testing ◽  
Other Hand

The efficiency of drilling and blasting operations can be assessed in different ways, depending on the desired effect. The evaluation can be performed on the basis of the quality of the explosives applied for rock extraction. On the other hand, the correct assessment should include the results of drilling and blasting works. One of the parameters that are commonly used in the quality assessment of explosives is the on-site testing of the detonation velocity, which is a direct indicator of the efficiency of explosives. The quality of explosives is essential for the appropriate blasting process and should be subjected to regular verification by means of measurements under different site conditions. Since in most cases the excavated rock must be transported from the blasting site to another location, one of the main parameters that can be used for drilling and blasting operations assessment is fragmentation analysis. It may be done using various image-based particles sizing software. The article presents selected methods that can be applied for the evaluation of blasting works efficiency, including measurements of detonation velocity as well as fragmentation analysis based on photogrammetric methods.

scholarly journals BEHAVIOUR OF THE "ATHENIAN SCHIST" IN EXCAVATION BY AN OPEN FACE SHIELD BORING MACHINE. EXTENSION LINE TO PERISTERI OF THE METROPOLITAN RAILWAY OF ATHENS.

2004 ◽  
Vol 36 (4) ◽  
pp. 1790
Author(s):  
Π. Μαρίνος ◽  
Β. Μαρίνος ◽  
Γ. Στούμπος ◽  
M. Νόβακ ◽  
K. Κορκάρης ◽  
...  
Keyword(s):  
Rock Mass ◽  
Shear Zones ◽  
Poor Quality ◽  
Remedial Measures ◽  
Rock Masses ◽  
Tectonic Disturbance ◽  
The Face ◽  
Open Face

The excavation of the Metropolitan Railway of Athens is being opening mainly through the system of "Athenian Schist" which basically is constituted by a sequence of schists and metasandstones and presents high heterogeneity and tectonic disturbance due to faults and shear zones. The excavation is either mechanized or conventional. This paper is focused on the extension line to Peristeri, where an OFS (Open Face Shield) ΤΒΜ was used. This machine is effective in controlling any instabilities in fair quality rock mass, but not when poor quality rock masses are present where the stand-up time is limited. In such cases immediate support of the face or even improvement of the quality of the material is necessary. In this paper a specific classification of "Athenian Schist" is described in order to provide predictions for the behaviour of the rock masses under the conditions of an excavation with an OFS and, to access the risks but also the need of remedial measures

Faktor-Faktor yang Berpengaruh dalam Mendapatkan Pekerjaan bagi Lulusan Statistika IPB dengan Menggunakan Metode CHAID

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Aulia Dwi Oktavia ◽  
Aam Alamudi ◽  
Budi Susetyo
Keyword(s):  
College Graduates ◽  
Influential Factors ◽  
Classification Model ◽  
Statistical Software ◽  
Waiting Period ◽  
Level Of Education ◽  
Economic Problems ◽  
Factors Influencing

Unemployment is one of the economic problems in Indonesia. Judging from the level of education that was completed there were unemployment from the level of college graduates. This encourages the level of competition in getting jobs to be more stringent, so that college graduates (bachelor of Statistics in IPB) must have the preparation of various factors to maintain the quality of their graduates. The quality of college graduates can be seen from the length of time waiting to get a job. This study aims to determine the influential factors in getting a job for graduates of the IPB Statistics degree, so that the CHAID method can be used in this study. The results of CHAID's analysis in this study in the form of tree diagrams using α = 10% explained that the factors influencing the waiting period variables were sex, internship, and the ability to master statistical software, where the accuracy value generated by the classification model was 79.3 %.

scholarly journals Health-Related Quality of Life among Cancer Survivors Depending on the Occupational Status

2021 ◽  
Vol 18 (7) ◽  
pp. 3803
Author(s):  
Kisook Kim ◽  
Hyohyeon Yoon
Keyword(s):  
Quality Of Life ◽  
Depressive Symptoms ◽  
Cancer Survivors ◽  
Occupational Status ◽  
Influential Factors ◽  
Health Related Quality ◽  
Factors Affecting ◽  
Related Quality ◽  
Health Related

The study aimed to identify and compare the factors affecting health-related quality of life (HRQoL) depending on the occupational status of cancer survivors. This study was a secondary data analysis from the Korea National Health and Nutrition Examination Survey (KNHANES) from 2014 to 2018. Hierarchical multivariate linear regression was used to investigate the factors affecting the HRQoL of each group. Non-working cancer survivors had significantly lower HRQoL than working cancer survivors (p < 0.001). A hierarchical multiple regression model showed that demographic, health-related, and psychological characteristics explained 62.0% of non-working cancer survivors’ HRQoL (F = 4.29, p < 0.001). Among the input variables, health-related characteristics were the most influential factors (ΔR2 = 0.274, F = 9.84, p < 0.001). For working cancer survivors, health-related characteristics were the only variable that was statistically associated with HRQoL (F = 5.556, p < 0.001). It is important to enhance physical activities and manage the chronic disease to improve the HRQoL of working cancer survivors. Further, managing health-related characteristics, including depressive symptoms and suicidal ideation, is necessary for non-working cancer survivors. Regarding working survivors, psychological factors such as depressive symptoms and suicidal tendencies did not affect HRQoL. Therefore, an early and effective return to work program should be developed for the improvement of their HRQoL.

Analysis of Unstable Rock-Mass Stability Based on Limit Equilibrium Method and Strength Reduction Method

2016 ◽  
Vol 858 ◽  
pp. 73-80
Author(s):  
Ying Kong ◽  
Hua Peng Shi ◽  
Hong Ming Yu
Keyword(s):  
Rock Mass ◽  
Failure Mode ◽  
Posterior Margin ◽  
Reduction Method ◽  
Limit Equilibrium ◽  
Limit Equilibrium Method ◽  
Strength Reduction ◽  
Strength Reduction Method ◽  
Rock Masses ◽  
Unstable Rock

With the slope unstable rock masses of a stope in Longsi mine, Jiaozuo City, China as the target, we computed and analyzed the stability of unstable rock masses using a limit equilibrium method (LEM) and a discrete element strength reduction method (SRM). Results show that the unstable rock masses are currently stable. Under the external actions of natural weathering, rainfall and earthquake, unstable rock mass 1 was manifested as a shear slip failure mode, and its stability was controlled jointly by bedding-plane and posterior-margin steep inclined joints. In comparison, unstable rock mass 2 was manifested as a tensile-crack toppling failure mode, and its stability was controlled by the perforation of posterior-margin joints. From the results of the 2 methods we find the safety factor determined from SRM is larger, but not significantly, than that from LEM, and SRM can simulate the progressive failure process of unstable rock masses. SRM also provides information about forces and deformation (e.g. stress-strain, and displacement) and more efficiently visualizes the parts at the slope that are susceptible to instability, suggesting SRM can be used as a supplementation of LEM.

scholarly journals Influence of the groundwater level on the bearing capacity of shallow foundations on the rock mass

2021 ◽  
Author(s):  
Ana Alencar ◽  
Rubén Galindo ◽  
Svetlana Melentijevic
Keyword(s):  
Rock Mass ◽  
Bearing Capacity ◽  
Groundwater Level ◽  
Sensitivity Study ◽  
Shallow Foundations ◽  
Unit Weight ◽  
Geological Strength Index ◽  
Strength Index ◽  
Mass Type

AbstractThe presence of the groundwater level (GWL) at the rock mass may significantly affect the mechanical behavior, and consequently the bearing capacity. The water particularly modifies two aspects that influence the bearing capacity: the submerged unit weight and the overall geotechnical quality of the rock mass, because water circulation tends to clean and open the joints. This paper is a study of the influence groundwater level has on the ultimate bearing capacity of shallow foundations on the rock mass. The calculations were developed using the finite difference method. The numerical results included three possible locations of groundwater level: at the foundation level, at a depth equal to a quarter of the footing width from the foundation level, and inexistent location. The analysis was based on a sensitivity study with four parameters: foundation width, rock mass type (mi), uniaxial compressive strength, and geological strength index. Included in the analysis was the influence of the self-weight of the material on the bearing capacity and the critical depth where the GWL no longer affected the bearing capacity. Finally, a simple approximation of the solution estimated in this study is suggested for practical purposes.

scholarly journals A 3DEC Numerical Analysis of the Interaction Between an Uneven Rock Surface and Shotcrete Lining

2021 ◽  
Author(s):  
Ping Zhang ◽  
Ering Nordlund
Keyword(s):  
Numerical Study ◽  
Support Effect ◽  
Influential Factors ◽  
Numerical Analyses ◽  
Numerical Code ◽  
Rock Surface ◽  
Stress Concentrations ◽  
Circular Tunnel ◽  
Rock Tunnels ◽  
Shotcrete Lining

AbstractRock tunnels excavated using drilling and blasting technique in jointed rock masses often have a very uneven and rough excavation surface. Experience from previous studies shows that the unevenness of a rock surface has a large impact on the support effect of shotcrete lining. However, clear conclusions regarding the effect of 2D and 3D uneven surfaces were not obtained due to limited studies in the literature. The numerical analyses reported in this paper were made to investigate the influence of the surface unevenness of a circular tunnel opening on the support effect of shotcrete using a 3D numerical code (3DEC). The models were first calibrated with the help of observations and measured data obtained from physical model tests. The influential factors were investigated further in this numerical study after calibration had been achieved. The numerical analyses show that, in general, the unevenness of a tunnel surface produces negative support effects due to stress concentrations in recesses (compressive) and at apexes (tensile) after excavation. However, shotcrete sprayed on a doubly waved uneven surface has better support effect compared to shotcrete sprayed on a simply waved tunnel surface. The development of shear strength (specifically frictional strength) on the uneven interface between the shotcrete and the rock contributes to this effect, in the condition where bonding of the shotcrete does not work effectively. The interface is a crucial element when the interaction between the rock and shotcrete is to be simulated. When an entire tunnel surface is covered by shotcrete with high modulus, more failures will occur in the shotcrete especially when rock surface is uneven. Based on the numerical model cases examined, some recommendations on how to incorporate tunnel surface conditions (2D or 3D unevenness) in the design of a shotcrete lining are given.

scholarly journals Solubility of cytoskeletal proteins in immunohistochemistry and the influence of fixation.

1993 ◽  
Vol 41 (4) ◽  
pp. 609-616 ◽  
Author(s):  
B M Riederer ◽  
R Porchet ◽  
R A Marugg ◽  
L I Binder
Keyword(s):  
Protein Solubility ◽  
Immunohistochemical Localization ◽  
Influential Factors ◽  
Cytoskeletal Proteins ◽  
Fixed Tissue ◽  
Aldehyde Fixation ◽  
Cat Brain ◽  
Spectrin Cytoskeleton ◽  
Cryostat Sections

For accurate and quantitative immunohistochemical localization of antigens it is crucial to know the solubility of tissue proteins and their degree of loss during processing. In this study we focused on the solubility of several cytoskeletal proteins in cat brain tissue at various ages and their loss during immunohistochemical procedures. We further examined whether fixation affected either solubility or immunocytochemical detectability of several cytoskeletal proteins. An assay was designed to measure the solubility of cytoskeletal proteins in cryostat sections. Quantity and quality of proteins lost or remaining in tissue were measured and analyzed by electrophoresis and immunoblots. Most microtubule proteins were found to be soluble in unfixed and alcohol fixed tissues. Furthermore, the microtubule proteins remaining in the tissue had a changed cellular distribution. In contrast, brain spectrin and all three neurofilament subunits were insoluble and remained in the tissue, allowing their immunocytochemical localization in alcohol-fixed tissue. Synapsin I, a protein associated with the spectrin cytoskeleton, was soluble, and aldehyde fixation is advised for its immunohistochemical localization. With aldehyde fixation, the immunoreactivity of some antibodies against neurofilament proteins was reduced in axons unveiling novel immunogenic sites in nuclei that may represent artifacts of fixation. In conclusion, protein solubility and the effects of fixation are influential factors in cytoskeletal immunohistochemistry, and should be considered before assessments for a quantitative distribution are made.

Numerical investigation of chatter suppression in milling using active fixtures in open-loop control

2016 ◽  
Vol 24 (9) ◽  
pp. 1757-1773 ◽  
Author(s):  
Lorenzo Sallese ◽  
Niccolò Grossi ◽  
Antonio Scippa ◽  
Gianni Campatelli
Keyword(s):  
Numerical Investigation ◽  
Removal Rate ◽  
Active Vibration Control ◽  
Open Loop ◽  
Influential Factors ◽  
Depth Of Cut ◽  
Control Logic ◽  
Loop Control ◽  
Testing Environment ◽  
Chatter Suppression

Among the chatter suppression techniques in milling, active fixtures seem to be the most industrially oriented, mainly because these devices could be directly retrofittable to a variety of machine tools. The actual performances strongly depend on fixture design and the control logic employed. The usual approach in the literature, derived from general active vibration control applications, is based on the employment of adaptive closed-loop controls aimed at mitigating the amplitude of chatter frequencies with targeted counteracting vibrations. Whilst this approach has proven its effectiveness, a general application would demand a wide actuation bandwidth that is practically impeded by inertial forces and actuator-related issues. This paper presents the study of the performance of alternative open-loop actuation strategies in suppressing chatter phenomena, aiming at limiting the required actuation bandwidth. A dedicated time-domain simulation model, integrating fixture dynamics and the features of piezoelectric actuators, is developed and experimentally validated in order to be used as a testing environment to assess the effectiveness of the proposed actuation strategies. An extensive numerical investigation is then carried out to highlight the most influential factors in assessing the capability of suppressing chatter vibrations. The results clearly demonstrated that the regenerative effect could be effectively disrupted by actuation frequencies close to half the tooth-pass frequency, as long as adequate displacement is provided by the actuators. This could sensibly increase the critical axial depth of cut and hence improve the achievable material removal rate, as discussed in the paper.

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