scholarly journals Impact of Shear Zone on Rockburst in the Deep Neelum-Jehlum Hydropower Tunnel: A Numerical Modeling Approach

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1935 ◽  
Author(s):  
Abdul Naji ◽  
Hafeezur Rehman ◽  
Muhammad Emad ◽  
Hankyu Yoo
Keyword(s):  
Stress Concentration ◽  
Shear Zone ◽  
High Stress ◽  
Side Wall ◽  
Shear Plane ◽  
Stress Conditions ◽  
Major Influence ◽  
Small Scale ◽  
Tectonically Active ◽  
The Right

Rockburst is a hazardous phenomenon in deep tunnels influenced by geological structural planes like faults, joints, and shear planes. Small-scale shear-plane-like structures have damaging impact on the boundaries of the tunnel, which act as barrier and accumulate high stresses. A shear plane combined with high stress conditions is very dangerous in deep excavations. Such a shear plane exposed in the side wall of the right headrace tunnel in the Neelum-Jehlum Hydropower Project. This project is constructed in the tectonically active Himalayas under high stress conditions. The influence of a shear zone on rockburst occurrence near the tunnel is studied. The FLAC3D explicit code simulated the shear zone in the right tunnel, revealing that the stresses are concentrated near the shear zone, while no such stress concentration is present in the left tunnel. The Rock mass got displaced near this shear zone. Modeling results confirm that the presence of shear zone in side wall of the right tunnel has a major influence on rockburst occurrence. A shear slip along this plane released huge amounts of accumulated energy, causing human fatalities and property damage. A comparison of numerical simulation with empirical rockburst criteria validates the actual conditions and help us to understand the phenomenon of stress concentration near the shear zone and its impact during deep tunneling.

scholarly journals Impact of Shear Zone on Rockburst in the Deep Neelum-Jehlum Hydropower Tunnel: A Numerical Modeling Approach

2018 ◽  
Author(s):  
Abdul Muntaqim Naji ◽  
Hafeezur Rehman ◽  
Zaka Emad ◽  
HanKyu Yoo
Keyword(s):  
Stress Concentration ◽  
Shear Zone ◽  
High Stress ◽  
Side Wall ◽  
Shear Plane ◽  
Stress Conditions ◽  
Major Influence ◽  
Small Scale ◽  
Tectonically Active ◽  
The Right

Rockburst is a hazardous phenomenon in deep tunnels influenced by geological structural planes like faults, joints, and shear planes. Small-scale shear-plane-like structures have damaging impact on the boundaries of the tunnel, which accumulate high stresses. Such a shear plane was exposed in the side wall of the right headrace tunnel in the Neelum-Jehlum Hydropower Project. This project is constructed in the tectonically active Himalayas with high stress conditions. A shear plane combined with high stress conditions is very dangerous in deep excavations. The influence of a shear zone on rockburst occurrence near a tunnel is studied. The FLAC3D explicit code simulated the shear zone in the right tunnel, revealing that the stresses are concentrated near the shear zone, with no stress concentration in the left tunnel, which has neither shear zone nor rockburst. Rock mass was displaced near this shear zone even before excavation. Modeling results confirm that the side wall shear zone of the tunnel has a major influence on rockburst occurrence. A shear slip along this plane released huge amounts of energy, causing human fatalities and property damage. A numerical simulation validates the actual conditions and helps us understand the phenomenon of stress concentration near the shear zone and its impact during deep tunneling.

scholarly journals Research on Optimization of Coal Pressure Relief Borehole Parameters under High-Stress Conditions

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Heng Zhang ◽  
Tie Li ◽  
Zhenhua Ouyang ◽  
Su Liu ◽  
Haiyang Yi
Keyword(s):  
Stress Concentration ◽  
Energy Density ◽  
Elastic Energy ◽  
Large Diameter ◽  
High Stress ◽  
Stress Conditions ◽  
Plastic Behavior ◽  
Coal Seams ◽  
Pressure Relief ◽  
Relief Area

Determining the parameters of boreholes drilled for relieving pressure in coal seams is the key preventing and controlling rock bursts in boreholes of large diameter. In this study, theoretical analysis, numerical simulation, literature research, and other analysis methods are applied to study the angles of elastic energy dissipation and stress transfer, the distribution law of the pressure relief area, and the areas of stress concentration, energy, stress, displacement, and plastic behavior of large-diameter pressure relief boreholes in coal seams under high-stress conditions. The results are then used to evaluate the relationship between large-diameter pressure relief boreholes and the borehole arrangement. The following results are obtained. (1) A large-diameter results in a large amount of elastic energy released by the surrounding coal, low residual elastic energy density, strong interaction between boreholes, large pressure relief range of the borehole, and high pressure relief efficiency. (2) The main evaluation factor of the borehole pressure relief effect is its thickness and stress concentration area; secondary evaluation is based on the areas of energy, displacement, stress, and plastic behavior. (3) Six evaluation index systems are established to evaluate the effects of borehole pressure relief, which are found to be the thicknesses of the borehole pressure relief area and stress concentration area, reduction degree of energy density, percentage of stress reduction, displacement, and penetration degree of the plastic area. (4) It is determined that when the diameters of the pressure relief boreholes are 100, 120, 180, and 200 mm, a single-row borehole arrangement is adopted; a three-pattern borehole arrangement is adopted with diameters of 140 and 160 mm. These research results can provide theoretical support in selecting reasonable borehole arrangements for pressure relief boreholes of different diameters.

Rock Burst Analyse in Qirehataer Diversion Tunnel

2011 ◽  
Vol 138-139 ◽  
pp. 352-355
Author(s):  
Jian Feng Bian ◽  
Jian Jun Zhou ◽  
Guo Bin Zhao
Keyword(s):  
Rock Burst ◽  
High Stress ◽  
Horizontal Stress ◽  
Stress Conditions ◽  
Diversion Tunnel ◽  
Gneissic Granite ◽  
High Stress Concentration ◽  
Tunnel Section ◽  
The Right ◽  
Brittle Rock Mass

Rock burst is a geological hazard which occurs when hard and brittle rock mass is excavated under high in-situ stresses or high stress concentration. The Qirehataer diversion tunnel has 15.66 km long at a maximum depth of 1720 m. About 64.5% of the tunnel is located in gneissic granite. During excavation of the tunnel, light to moderate rock burst occurred in about 300 m length of the tunnel. This paper provides the analysis of the characteristics and stress conditions in the rock burst site using the stress conditions around the excavation, and provides an explanation on the reasons why rock burst occurred from the beginning to middle of the vault on the right side of the tunnel section, and the most serious situation is located at 60° with respect to horizontal. Stress release hole and bolt or bolt and net are used to prevent and manage rock burst which have been shown to be effective in this case.

Self-Injurious Behavior vs. Nonsuicidal Self-Injury

Crisis ◽  
2012 ◽  
Vol 33 (2) ◽  
pp. 106-112 ◽  
Author(s):  
Christopher M. Bloom ◽  
Shareen Holly ◽  
Adam M. P. Miller
Keyword(s):  
Positive Reinforcement ◽  
Empirical Investigation ◽  
High Stress ◽  
Animal Research ◽  
Stress Conditions ◽  
Human Populations ◽  
Pharmacological Interventions ◽  
Self Injury ◽  
Cns Stimulant ◽  
Nonsuicidal Self Injury

Background: Historically, the field of self-injury has distinguished between the behaviors exhibited among individuals with a developmental disability (self-injurious behaviors; SIB) and those present within a normative population (nonsuicidal self-injury; NSSI),which typically result as a response to perceived stress. More recently, however, conclusions about NSSI have been drawn from lines of animal research aimed at examining the neurobiological mechanisms of SIB. Despite some functional similarity between SIB and NSSI, no empirical investigation has provided precedent for the application of SIB-targeted animal research as justification for pharmacological interventions in populations demonstrating NSSI. Aims: The present study examined this question directly, by simulating an animal model of SIB in rodents injected with pemoline and systematically manipulating stress conditions in order to monitor rates of self-injury. Methods: Sham controls and experimental animals injected with pemoline (200 mg/kg) were assigned to either a low stress (discriminated positive reinforcement) or high stress (discriminated avoidance) group and compared on the dependent measures of self-inflicted injury prevalence and severity. Results: The manipulation of stress conditions did not impact the rate of self-injury demonstrated by the rats. The results do not support a model of stress-induced SIB in rodents. Conclusions: Current findings provide evidence for caution in the development of pharmacotherapies of NSSI in human populations based on CNS stimulant models. Theoretical implications are discussed with respect to antecedent factors such as preinjury arousal level and environmental stress.

Fatigue Failure Analysis Using the Theory of Critical Distance

2011 ◽  
Vol 462-463 ◽  
pp. 663-667 ◽  
Author(s):  
Ruslizam Daud ◽  
Ahmad Kamal Ariffin ◽  
Shahrum Abdullah ◽  
Al Emran Ismail
Keyword(s):  
Stress Concentration ◽  
Fatigue Failure ◽  
Notch Root ◽  
High Stress ◽  
Critical Distance ◽  
Future Research ◽  
Element Analysis ◽  
Linear Elastic ◽  
The Finite Element Analysis ◽  
Elastic Fracture

This paper explores the initial potential of theory of critical distance (TCD) which offers essential fatigue failure prediction in engineering components. The intention is to find the most appropriate TCD approach for a case of multiple stress concentration features in future research. The TCD is based on critical distance from notch root and represents the extension of linear elastic fracture mechanics (LEFM) principles. The approach is allowing possibilities for fatigue limit prediction based on localized stress concentration, which are characterized by high stress gradients. Using the finite element analysis (FEA) results and some data from literature, TCD applications is illustrated by a case study on engineering components in different geometrical notch radius. Further applications of TCD to various kinds of engineering problems are discussed.

scholarly journals Stress level effect on mobility of dry granular flows of angular rock fragments

Landslides ◽  
2021 ◽  
Author(s):  
B. Cagnoli
Keyword(s):  
Stress Level ◽  
Granular Flow ◽  
High Stress ◽  
Granular Flows ◽  
Flow Dynamics ◽  
Small Scale ◽  
Flow Volume ◽  
Rock Fragments ◽  
Rock Avalanches ◽  
Flow Mobility

AbstractGranular flows of angular rock fragments such as rock avalanches and dense pyroclastic flows are simulated numerically by means of the discrete element method. Since large-scale flows generate stresses that are larger than those generated by small-scale flows, the purpose of these simulations is to understand the effect that the stress level has on flow mobility. The results show that granular flows that slide en mass have a flow mobility that is not influenced by the stress level. On the contrary, the stress level governs flow mobility when granular flow dynamics is affected by clast agitation and collisions. This second case occurs on a relatively rougher subsurface where an increase of the stress level causes an increase of flow mobility. The results show also that as the stress level increases, the effect that an increase of flow volume has on flow mobility switches sign from causing a decrease of mobility at low stress level to causing an increase of mobility at high stress level. This latter volume effect corresponds to the famous Heim’s mobility increase with the increase of the volume of large rock avalanches detected so far only in the field and for this reason considered inexplicable without resorting to extraordinary mechanisms. Granular flow dynamics is described in terms of dimensionless scaling parameters in three different granular flow regimes. This paper illustrates for each regime the functional relationship of flow mobility with stress level, flow volume, grain size, channel width, and basal friction.

The State Policy towards the Homeless in Moldova between the ‘Left Hand’ and the ‘Right Hand’. The Case of Chișinău Shelter

Südosteuropa ◽  
2019 ◽  
Vol 67 (2) ◽  
pp. 175-195
Author(s):  
Petru Negură
Keyword(s):  
Homeless People ◽  
Severe Disabilities ◽  
The State ◽  
Small Scale ◽  
Left Hand ◽  
Right Hand ◽  
Binary Approach ◽  
The One ◽  
The Right ◽  
Depth Interviews

Abstract The Centre for the Homeless in Chișinău embodies on a small scale the recent evolution of state policies towards the homeless in Moldova (a post-Soviet state). This institution applies the binary approach of the state, namely the ‘left hand’ and the ‘right hand’, towards marginalised people. On the one hand, the institution provides accommodation, food, and primary social, legal assistance and medical care. On the other hand, the Shelter personnel impose a series of disciplinary constraints over the users. The Shelter also operates a differentiation of the users according to two categories: the ‘recoverable’ and those deemed ‘irrecoverable’ (persons with severe disabilities, people with addictions). The personnel representing the ‘left hand’ (or ‘soft-line’) regularly negotiate with the employees representing the ‘right hand’ (‘hard-line’) of the institution to promote a milder and a more humanistic approach towards the users. This article relies on multi-method research including descriptive statistical analysis with biographical records of 810 subjects, a thematic analysis of in-depth interviews with homeless people (N = 65), people at risk of homelessness (N = 5), professionals (N = 20) and one ethnography of the Shelter.

FAKTOR PENANGULANGAN TERJADINYA WASTE PADA PROYEK KONSTRUKSI DI SURABAYA

EXTRAPOLASI ◽  
2020 ◽  
Vol 17 (2) ◽  
pp. 1-10
Author(s):  
Michella Beatrix ◽  
Nurul Rochmah ◽  
Gede Sarya ◽  
Pebru Dwijayanto
Keyword(s):  
Waste Management ◽  
Construction Projects ◽  
Positive Impact ◽  
Scale Construction ◽  
Small Scale ◽  
Construction Costs ◽  
Warehouse Storage ◽  
The Right ◽  
The Impact ◽  
Material Requirements

AbstractLarge and small scale construction projects have waste that cannot be predicted in advance, even the amount cannot be predicted directly, whether it is in large or small amounts. The existence of waste can have a significant impact that can affect construction costs. Waste can have both negative and positive impacts. Good waste management will have a positive impact on the company in terms of cost, even time, and quality, but if the waste that occurs cannot be handled or managed properly it will harm the company in terms of cost, time, and even in terms of quality. In this case, the party that always gets the impact of the waste is the contractor.This study focuses on mitigating the occurrence of waste that is how to minimize it. Thisstudy uses the distribution of questionnaires to the contractor in Surabaya. The results of this study are 5 item indicators on how to minimize the highest ranking. The 5 items are Updating material requirements, Mixing, transporting, and placing concrete at the right time, Increasing the competence and expertise of labor, Provision of good and adequate material/warehouse storage facilities, and accurate material measurement.  Abstrak Proyek konstruksi dalam skala besar maupun kecil, memiliki waste yang tidak dapat diprediksi sebelumnya, bahkan jumlahnya pun tidak dapat diprediksi secara langsung, apakah itu dalam jumlah besar ataupun jumlah yang kecil. Adanya waste dapat memberikan dampak yang signifikan yang dapat mempengaruhi biaya konstruksi. Pada dasarnya waste dapat memberikan dampak negatif maupun positif. Pengelolaan waste yang baik akan memberikan dampak positif bagi perusahaan dalam segi biaya, bahkan waktu dan mutu, namun apabila waste yang terjadi tidak dapat diatasi atau dikelola dengan baik maka akan memberikan dampak negatif bagi perusahaan dalam segi biaya, waktu bahkan dalam hal mutu. Dalam hal ini pihak yang selalu mendapatkan dampak dari adanya waste adalah pihak kontraktorPenelitian ini memfokuskan pada faktor penanggulangan terjadinya waste yaitu cara meminimalisirnya. Penelitian ini menggunakan penyebaran kuisioner kepada pihak kontraktor di Surabaya. Hasil dari penelitian ini adalah 5 item indicator cara meminimalisir yang memiliki ranking tertinggi. 5 item tersebut adalah Updating kebutuhan material, Mencampur, mengangkut dan menempatkan beton pada waktu yang tepat, Meningkatkan kompetensi dan keahlian tenaga kerja, Penyediaan fasilitas penyimpanan material/gudang yang baik dan memadai, dan Pengukuran bahan yang akurat.

scholarly journals Efficiency Comparison between Conventional and Modern Port Operation System for Small-Scale Dry Bulk Cargo

2018 ◽  
Vol 147 ◽  
pp. 05004
Author(s):  
Aulia Tiara ◽  
Julfikhsan Ahmad Mukhti
Keyword(s):  
Maintenance Cost ◽  
Small Scale ◽  
Cost Ratio ◽  
Operation System ◽  
Financial Assessment ◽  
Benefit Cost Ratio ◽  
Port Operation ◽  
Efficiency Comparison ◽  
Efficient Option ◽  
The Right

Since the launching of Sea Toll Road Program in 2015, the improvement in ports’ operation systems has become Indonesia’s foremost necessity. This improvement commonly leads to equipment modernization, while realistically, modern equipment does not always amount to a productive performance, especially in the context of small-scale ports. Instead, it is prone to creating wasteful capital and maintenance cost as well as making the planning time ineffective. This study compares two options of port operation systems in a small port, which is conventional and technologically-advanced method for dry bulk cargo. It results in thin gaps between each option’s financial assessment variables, which are Internal Rate of Return, Benefit/Cost Ratio and Payback Period, regardless of a stark difference between each option’s equipment cost. This study concludes that with the right approach, the conventional operation system is still the most efficient option compared to its contemporary opposite.

Crack Growth During Full Scale Reeling Simulation of Pipes With Girth Welds

2004 ◽  
Author(s):  
Oddvin O¨rjasaeter ◽  
Olav Jan Hauge ◽  
Guy Ba¨rs ◽  
Per Egil Kvaale
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
High Strain ◽  
High Stress ◽  
Strain Range ◽  
Full Scale ◽  
Small Scale ◽  
Final Fracture ◽  
Lack Of Fusion ◽  
Girth Welds

Installation of pipelines by reeling has proved to be an effective method. However, the pipe bending results in very high stress and strain and cannot be handled by conventional design rules, as stated in design codes, e.g. [2]: High strain crack growth must be assessed according to specific case-by-case selected criterions. In the present work the performance of 10” and 12 3/4” pipes with typical weld defects is studied — from initiation of cracks at notches to final fracture. Information was obtained from several sources: full scale cyclic bending of pipes, FE simulations, and small-scale tests. The plasticity during reeling operations results in substantial non-linear behavior due to varying cross section properties, cyclic creep, and different material response at tensile and compression side of the pipe. Hence, a full scale reeling simulation must be carefully planned and include sufficient tolerances. Critical cracks in pipe girth welds initiate mainly from the surface (undercuts, lack of penetration, or lack of fusion), but potentially also internally (lack of fusion or large pores). Various configurations of these parameters were investigated in full scale pipe tests. It was possible to verify both crack propagation during the reeling cycles, and the point of final fracture (for ECA verifications). In pipe design on must assure safe conditions for both reeling operations and for later in-service loading. Proper design tools must be available. Several methods for high strain crack growth analysis were considered and also compared to small-scale specimen data. Conventional strain-life methodology failed to predict the crack propagation accurately. A new approach including a tensile strain range parameter offered promising results.

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