Wedge Cut Research Articles

A newly developed blasting cut in tunnels; application of “combined method” in small to medium-sized tunnels

Drilling and blasting method have been widely used for driving tunnels in hard rock. When designing a blast operation especially in case of long tunnels, the primary objective of contractors is to ensure optimized blast parameters for achieving the most economical and time-saving technique of excavation. Choosing a proper blasting cut has a crucial role in the successfulness of the whole blast round in terms of quality, time and cost. The first aim of cut is to break and throw rocks and create a cavity for the upcoming production detonators. An attempt has been made here to test and develop an innovative cutting system for small to medium-scale tunnels where classical wedge cut is physically difficult to execute; what is called in this paper “combined or quasi-wedge method”. Proposed drilling and blasting patterns have been first put in computerized drilling machines and then tested in the tunnels located in Rishikesh-Karnaprayag Railway Project, Package 2, driven in sedimentary rock mass. After thorough investigation of trial-and-error blasts economically and technically, necessary changes have been made to guarantee optimization and find proper design configurations. In comparison to conventional parallel cut, the newly developed cut leads not only to the betterment of cycle time for excavation but also improvement of specific drilling and specific charge, the two main performance indicators of blast operations. Vibration, fragmentation, pull length, fly rock and profile quality, as pro-blast parameters, were also found highly satisfactory.

Theory and numerical simulation of deep hole cut blasting based on dispersed charge and staged detonation

The rock drilling and blasting method is the most commonly adopted method for rock roadway excavation in China, where cutting efficiency is the key factor affecting the excavation speed. The conventional wedge-shaped cut blasting is not suitable for deep hole blasting since the method requires the explosives to be concentrated at the bottom of the borehole, resulting in uneven fragmentation of the upper rock and difficulty in throwing the bottom rock. In addition, the cut area is small, and the range of cavity created after cut hole blasting cannot meet the needs of large section blasting tunneling. This present study proposes an efficient method for charging and detonation inside and between boreholes called disperse charge and staged detonation (DCSD) cut blasting technique. The DCSD cut blasting and traditional wedge cut blasting models were established and compared using the smooth particle hydrodynamics-finite element method (SPH-FEM). The results shows that the DCSD model reduces the minimum resistance line of rock blasting and creates a new free surface, promoting the throwing of the bottom rock mass and the overall rock mass failure. Furthermore, the cutting efficiency is defined to quantitatively analyze the influence of different parameters on the cutting effect. The cutting efficiency of the DCSD model with dispersed charge is 21.89% higher than that of the blasting model with continuous charge. The cutting effect is at its greatest for the three types of ε designed for the study, when ε = 0.5. The increase in hole depth reduces the cutting efficiency marginally, although it is still higher than that in the traditional mode. Finally, the successful application of digital electronic detonator and DCSD in domestic rock roadway blasting construction verifies the applicability of DCSD and provides a reference for subsequent projects involving rock roadway deep hole drilling and blasting construction.

Study on Optimization of Delay Method of Wedge Cut Blasting in Tunnel

Relying on the entrance section of a high-speed railway tunnel blasting project, the fluid-solid coupling algorithm based on ANSYS/LS-DYNA was used to optimize the parameters of wedge cut blasting, and the vibration could be reduced on the basis of ensuring the blasting effect. Through the combination of visual numerical simulation results and rock-breaking mechanism of wedge cut blasting, the maximum vibration velocity of different monitoring points in the model under different segmented time delay was analyzed. The results show that the best method for detonation is dividing the blastholes into three segments from upper to lower and dividing the left and right symmetrical blastholes into one segment. When the delay time is 10 ms, the average vibration reduction ratio is the best, which is reduced by 18% compared with the six-hole simultaneous blasting. In addition, the actual surrounding rock stress has a clamping effect on the cut blasting area. The wedge cut blasting footage obtained by numerical simulation was basically consistent with the field results, which proved that the model is reasonable and effective. This study intuitively and accurately demonstrated the process of cut blasting, the superposition curve of vibration velocity and the vibration reduction results under different delay times, and the effect of cut blasting. The results can be directly applied to similar projects, and the optimal blasting parameters and related issues can be solved more accurately with the help of this engineering analysis method.

Study of the Double Wedge Cut Technique in Medium-Depth Hole Blasting of Rock Roadways

A double wedge cut was used to improve the cut effects in the medium-depth hole blasting of rock roadways. First, the cavity formation mechanisms of single wedge cut and double wedge cut were analysed theoretically. The results show that the cavity formation resistance of the second-order wedge cut is reduced by the first-order wedge cut. Second, simulations of the two cut modes were conducted, which visualize the stress wave evolution and indicate that the stress wave of the first-order cut holes can cause pre-damage to the rock mass in the second-order cut cavity. A comparison of the stress field distribution shows that the first-order cut holes significantly increase the stress field intensity within 0 ~ 1.6 m to enhance the failure of the rock mass in the first-order cut cavity. Hence, the rock mass in the first-order cut cavity can easily be thrown out to create a new free face, which reduces the clamping effect of the second-order wedge cut and exacerbates the tensile failure of the rock mass in the second-order cut cavity. Thus, the difficulty of second-order wedge cut is reduced. Finally, blasting experiments were performed in a rock roadway. Using the double wedge cut, the average footage increased by 0.31 m, the average utilization rate of blastholes increased by 12.4%, and the average specific charge decreased by 0.20 kg·m−3, which proves the superiority of this cut mode.

Efficiency in Brain Removal Techniques: A Potentially Novel Approach

Dissection of the human brain is an important part of health professional education in the neuroscience curriculum. Therefore, it is critical that adequate protocols are utilized to preserve structures when removing brains from cadavers. Previous studies have looked at approaches to extracting the brain and associated structures from the cranial cavity which would best preserve these delicate structures. However, these methods require both extensive dissection experience and more time than suitable for routine use. The aim of this study was to determine the technique for brain removal that minimized the time required for the procedure while preserving key structures for future educational purposes.The time and ease for three aspects of brain extraction were assessed: removal of the calvaria, subsequent removal of the brain, and transection of the brainstem. Six dissectors (two faculty, four senior graduate students) with prior experience performed the removals. Each tested three calvaria‐removal approaches – circumferential only, circumferential plus a median cut, and circumferential plus a coronal cut. They also tested three approaches to brainstem transection—superiorly through the foramen magnum, inferiorly below C1 vertebra, or inferiorly after removal of an occipital wedge. The time for each procedure was recorded, and its ease was evaluated on a 5 point scale (1 easiest and 5 hardest). The combination of calvaria and brainstem approaches and the order of completion were randomized across dissectors and the 3 brains extracted by each. At the completion of brain removal, all brains were evaluated by two neuroscience course directors for utility in educational contexts. The evaluators rated structures on a list compiled from the laboratory handouts in the medical neuroscience course.Preliminary examination of the data suggests that removal of the calvaria using only the circumferential cut or using an additional coronal cut took about the same length of time, whereas performing circumferential and median cuts took somewhat longer. However, the ease of removal was greater when either the additional median or coronal cut was employed. Transecting the brainstem took less than a minute if performed through the foramen magnum or below C1, but it took substantially longer if the occipital wedge cut was executed. The ease of transection was greatest when performed below C1, and least when the occipital wedge was removed. There was no clear difference in overall quality of the brains removed by the various techniques.While there may be advantages to one or the other of the techniques for preservation of specific structures, it appears that all approaches tested were equivalent in yielding brains that could be used for educational purposes.

The ANP-Fuzzy-TOPSIS model for the optimization of the scheme of large-section blasting

In view of the difficulty of decision-making in the scheme selection of a bauxite mine in extensive section blasting, it is combined with analytic network process (ANP), fuzzy theory, and TOPSIS theory. The establishment of ANP-Fuzzy-TOPSIS comprehensive evaluation index system of comprehensive evaluation model can optimize the 3 selections of blasting scheme. From the 10 indicators of careful consideration of the impact of blasting scheme selection factors of 3 aspects of economy, technology, and safety, through the analytic hierarchy process, it objectively determines the weight vector of each evaluation index. Then, combined with the theory of fuzzy mathematics and the ideal construction of ANP-Fuzzy-TOPSIS comprehensive evaluation model solution method principle, the comprehensive evaluation index of each scheme calculate is calculated based on the superior degree. The selected cutting scheme is superior to 49.8%, 51.3%, and 48.4% to determine the second kinds of blasting scheme (double wedge cut) optimal. The results of this study are consistent with the results of BP neural network method, catastrophe progression method, and AHP-TOPSIS model, which prove the feasibility of the model.

A Study on Cut Blasting with Large Diameter Charges in Hard Rock Roadways

To overcome the problems of poor cutting effects in hard rock roadways, a cut blasting technique with large diameter charges was developed; that is, the cut holes employ 50 mm diameter blast holes and 45 mm diameter explosive sticks, while the other holes adopt 42 mm diameter blast holes and 35 mm diameter explosive sticks. First, the effect of charge diameter on damage range and cut cavity formation was analyzed. Next, simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. Finally, field tests were conducted to verify the viability of this technique. The results indicate that large diameter charges can increase the damage range around cut holes to improve the fragmentation degree of the rock mass in the cut cavity and significantly enhance the cavity formation power to better expel the rock mass fragments. The stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and hence increases the damage degree of the rock mass. In this study, the use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Therefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes.

Analysis of the Cavity Formation Mechanism of Wedge Cut Blasting in Hard Rock

The basic process of cut blasting is to break rock, throw fragments, and form a cavity. Based on the characteristics of cut blasting and the combined effect of stress waves and detonation gas, the evolution process of wedge cut blasting is divided into two stages, and a theoretical model is proposed to investigate the cavity formation mechanism by theoretical analysis and field tests. In phase one, rock breaking is caused by stress waves. By considering the dynamic strength of the rock, a computational model is built for the rock failure zone derived from the coupled cylindrical charge explosion. In phase two, the driving force of the detonation gas overcomes the total resistance of the surrounding rock mass, accelerates fragments, and then throws fragments to form a cavity. The criterion of cavity formation is established on the basis of the quasi‐static loading of the detonation gas. The theoretical model provides an overall interpretation of the cavity formation mechanism, in which stress waves break rock and detonation gas throws fragments. A specific case indicates that the range of the failure zone is approximately 18 times the borehole radius in granite and that the hole‐bottom spacing of the wedge cut can be designed as 50 cm; in addition, detonation gas is sufficient to overcome the total resistance, accelerate rock fragments, throw fragments, and form a cavity. Field tests present favourable blasting results, with a high utilization rate of boreholes and uniform fragment sizes. Therefore, the model could provide theoretical support and technical guidance for wedge cut blasting in hard rock.

Estimating the impact of income tax on personal savings in Serbia: The two channels approach

This paper provides an empirical evaluation of the effects of income taxation on personal savings in Serbia, by taking into account both transmitting channels: the direct impact of capital income tax on the rate-of-return and the indirect impact of labour income tax on disposable income. The estimated elasticity of bank deposits to the rate of return of 0.3 and the estimated elasticity of employment income to a labour tax wedge of −0.38 suggest that income tax function aimed at minimising the efficiency losses should not considerably differentiate the tax burden on labour and capital income. We show that in the case of the introduction of a revenue-neutral income tax, with a single marginal tax rate of 15% and considerably larger labour income exemption, households’ savings in Serbia would decline by 0.27%. This means that the negative impact of a rise in the capital income tax wedge on savings would prevail over the positive effects of a labour tax wedge cut. The results imply that the overall possibility to boost savings using tax policy is modest.

The interaction between the labour tax wedge and structural reforms in Italy

We present a quantitative analysis of Italian fiscal and structural reforms using the Prometeia Dynamic Stochastic General Equilibrium (DSGE) model to identify the optimal reform mix to boost growth and employment. We find that structural reforms via a reduction in price and wage markups and a labour tax wedge cut can provide a strong stimulus to the economy by increasing GDP and employment levels. The balanced budget constraint shows that to offset the decreased revenue due to the labour wedge cut, a reduction in public lump-sum transfers or a tax shift from labour to consumption or property is preferred over a cut in public spending on goods and services. Conversely, under simultaneous fiscal and structural reforms, the best payoff would be obtained from an expansion to public spending. Finally, we find that public investment works to magnify this effect in the long run.

Digital Measurements of 120 Mandibular Angles to Determine the Ideal Fibula Wedge Osteotomy to Re-Create the Mandibular Angle for Microvascular Reconstruction

Mandibular reconstruction continues to be a challenge, even for the seasoned reconstructive surgeon. The present study sought to determine the normal anatomic mandibular angle and to establish a predictable angle of resection for the fibula bone cut to re-create the neomandibular body-ascending ramus angle. A total of 30 random male and female panoramic radiographs were selected from our database. The selection criteria included age older than 21 years and a full or near total complement of teeth. The exclusion criteria were an edentulous mandible or maxilla, a history of trauma or maxillary or mandibular pathologic features, and age younger than 21 years. A total of 120 total measurements were performed. The angle measured was determined from a line coinciding with the posterior border of the ramus and the lower mandibular border. The measurements were taken from each side and from each gender group. The institutional review board of our institution approved the present study. The mean female mandibular right angle was 122.62°, and the left was 124.59° (average, 123.61°). The mean male mandibular right angle was 122.66°, and the left was 124.2° (average, 123.43°). The mean and median values were very similar. A statistically significant difference was identified between the left and right sides but not between the genders. Given this information, one can calculate a wedge cut in the fibula of about 56° to re-create the mean mandibular angle. This information can be used to make predictable fibula wedge closing osteotomies to re-create the normal mandibular ascending ramus body angle in a low-cost manner with the aid of an autoclavable metal wedge of 56°. This method would obviate the need for costly prefabricated guides.

Avaliação da segurança e ocorrência de defeitos na operação de corte semimecanizado de florestas de eucalipto

Avaliou-se a operação de corte semimecanizado nos aspectos de segurança no trabalho de operadores de motosserra e na qualidade da madeira derrubada, visando validar as recomendações técnicas da literatura especializada. O estudo foi realizado em povoamentos de Eucalyptus grandis com idade de 9 anos plantados em espaçamento 3 x 2 m, na Estação Experimental Fazenda Água Limpa (FAL), pertencente à Universidade de Brasília. Foram estabelecidos procedimentos relativos à técnica de derrubada de árvores. O tratamento-testemunha foi executado segundo as recomendações técnicas da literatura especializada. Os demais tratamentos variaram em relação à profundidade e ângulo de execução da boca de corte e, também, à altura de execução do corte de queda das árvores. Avaliaram-se a segurança da operação, ocorrência de rachaduras de topo, formação de espetos e volume de madeira remanescente na cepa, sendo os tratamentos comparados pelo teste de Dunnett. Pelos resultados, o tratamento-testemunha mostrou-se a melhor alternativa técnica para a derrubada de árvores de eucalipto com motosserra, nos aspectos de segurança e qualidade da madeira.

Culture of omentum-induced regenerating liver yielded hepatocyte-committed stem cells

Earlier we showed that when omentum, activated by inert particles, is allowed to fuse to a wedge cut in the liver, it induces stem cell proliferation in the liver resulting in massive liver regeneration. Here, we attempt to culture stem cells from the omentum-induced regenerating liver tissue. Cells from regenerating liver tissue were harvested and cultured. Cultured cells were characterized by immune staining, fluorescence activated cell sorting analysis, growth factor assay, in vitro differentiation, and their ability to engraft to injured sites in vivo. Culture yielded cells with a mesenchymal stem cell phenotype that could be maintained in culture indefinitely. These cells, called regenerating liver stem cells, expressed both adult and embryonic stem cell markers, secreted high levels of vascular endothelial growth factor, and expressed albumin. When grown on matrigel in the presence of hepatocyte growth factor, these cells differentiated into hepatocyte-like cells in culture, but they did not differentiate to adipogenic and osteogenic lineages when grown in specific differentiation medium. The differentiated cells expressed α-fetoprotein and secreted high levels of albumin and urea. After systemic injection, the undifferentiated cells engrafted only to the injured sites in the liver and not to the normal areas of the liver. In conclusion, omentum-induced regenerating liver yields hepatocyte-committed stem cells in culture. Such cells could prove to be useful in cell transplantation therapies.

Supramalleolar Osteotomies and Angular Corrections

Supramalleolar osteotomy is a well-described procedure for both congenital and acquired pediatric foot and ankle disorders. Its use in the adult population is also described but less well documented. The goal remains to achieve a plantigrade foot with decreased pain. The technique itself has many variations, and although the typical osteotomy is performed through the distal tibial metaphysis, the shape of the osteotomy, the type of wedge cut (opening or closing), and the associated fibular osteotomy can all vary.

CFIRP: What we learned in the first ten years

In response to public dissatisfaction with forest management methods, we initiated the College of Forestry Integrated Research Project (CFIRP) to test alternative silvicultural systems in Douglas-fir (Pseudotsuga menziesii) stands in western Oregon. We compared costs and biological and human responses among a control and three replicated silvicultural alternatives to clearcutting that retained structural features found in old Douglas-fir forests. Treatments were applied within 8- to 15-ha stands and attempted to mimic crown fires (modified clearcut), windthrow (green tree retention), and small-scale impacts such as root rot diseases (small patch group selection). We also compared costs in three unreplicated treatments (large patch group selection, wedge cut, and strip cut). Each treatment included differences in the pattern of retained dead trees (snags), as either scattered individuals or as clumps. Good communication among researchers and managers, a long-term commitment to the project, and careful documentation of research sites and data are important to the success of long-term silvicultural research projects. To date, over 30 publications have resulted from the project. Key words: alternative silviculture, data management, Douglas-fir, green tree retention, harvesting costs, human dimensions, Oregon, Pseudotsuga menziesii, recreation, wildlife

Blast performance in small tunnels - a critical evaluation in underground metal mines

Tunnels can be classified by size as small, medium or large. Blast design parameters and blast performance are considerably influenced by tunnel size. Though parallel cut is more suitable for a higher advance in small drivages, wedge cut proved to be more productive than parallel cut in the small drivages of a manganese mine (no. 1) because of the need for greater charge and more holes per unit of cut area. A double wedge cut pattern is suggested èfor improved blast results in these drivages. Analyses of blast results in around 600m of small rectangular tunnels driven in the host rock and the ore body of two metal mines led to development of an empirical relation for precise prediction of powder factor and specific drilling with wedge cut and parallel cut considering rock strength parameter, Q and hole depth.

An Improved Technique for Making Wedge Grafts in Soybean Plants1

AbstractThe design and use of a grafting block for making uniform and reproducible wedge grafts in soybean (Glycine max (L.) Merr.) plants is presented. The grafting block was prepared from plexiglass measuring 14 ✕ 10 ✕ 1.2 cm. A slot to hold the scion was cut at a 2.5‐degree angle to the face of the block. The slot measured 4 cm in length, 0.3 cm in width, and varied in depth from 0.15 cm at the edge of the block to 0.0 cm at its termination point. The slot enabled a precise positioning of the scion for making the wedge cut. The block was used to successfully produce grafted plants which vary in the number of scions and roots. Six wedge grafts with different top:root ratios are described. The grafting block reduced the time required to make a graft and it gave an increase in the survival percentage of grafts. The uniformity of the wedge graft facilitated the interfacing of the scion‐root stock tissues, resulting in a more rapid recovery and uniform growth of the plant.