Entry Width Research Articles

Wildfire and Climate Impacts Tree Hollow Density in a Temperate Australian Forest

Tree hollows are an important landscape resource used by fauna for shelter, nesting, and predator avoidance. In fire-prone landscapes, wildfire and climate may impact hollow dynamics; however, assessments of their concurrent impacts are rare. We conducted a field survey at 80 sites in the Sydney Basin bioregion (Australia) to understand how fire frequency, fire severity, mean annual temperature, and mean annual precipitation concurrently impacted the site-density of small- (<5 cm entry width), medium- (5–10 cm entry width) and large-size (>10 cm entry width) tree hollows and tree basal scars (which mediate hollow formation via invertebrate access to heartwood), when tree-size and dead/live status were considered. A unimodal relationship occurred between medium- and large-sized hollow densities and fire frequency and severity, respectively, with hollow densities greatest at intermediate frequencies/severities. Increases of 1.82, 1.43, and 1.17 hollows per site were observed between the 1 (reference) and 2, 2 and 3, and 3 and >3 fire frequency categories. Increases of 1.26, 1.75 and 0.75 hollows per site were observed between the low (reference) and moderate, moderate and high, and high and very high fire severity categories. Fire severity was also positively associated with basal scar density, with increases of 2.52, 8.15, and 8.47 trees per site between the low (reference) and moderate, moderate and high, and high and very high categories. A weak positive and stronger negative association was observed between mean annual temperature and small-sized hollow and basal scar density, respectively. Dead and medium-sized tree density was positively associated with medium-sized hollow and basal scar tree density, respectively. Collectively, our results suggest that wildfires, and in some cases climate, have diverse and size-specific impacts on tree hollow and basal scar density. Our results imply that fire regimes that allow for moderately severe wildfire will promote larger-sized tree hollows, which are a limiting resource for many fauna species.

Developing empirical model with graphical tool to estimate and predict capacity of rural highway roundabouts

Transportation infrastructure plays a significant role in the economic growth of developing countries where heavy vehicles act as the backbone in transporting goods and people via highways. However, presence of heavy vehicles in traffic stream lowers the overall operating speed and flow in rural highways especially at the vicinity of intersections. This research aims at developing an empirical model for estimating and predicting capacity of highway roundabouts considering both geometric and traffic parameters. Based on data collected from six roundabouts along the national highways in Bangladesh, multivariate regression method has been used to develop an empirical model as a function of entry width, rotary lane width, distance between entry and nearest exit, central island diameter, and circulating traffic flow to estimate and predict the capacity of rural highway roundabouts. For incorporating the presence of heavy vehicles in the model, all vehicle types are converted to passenger car equivalent units. A comparative study with established methods (i.e., HCM 2016, TRRL, IRC and German method) proves the superiority of the developed model in terms of predictive capacity. Furthermore, a Python based program called PyNomo, has been executed with the help of several add-on packages (e.g., numpy, scipy, pyx) to generate a compound parallel scale nomograph consisting of multiple variables using the developed empirical model. Considering the impact of heavy vehicles in the socio-economic development of a country, the nomograph will aid the practitioners and engineers as a quick and easily interpretable graphical tool for planning and designing roundabouts in rural highways.

Research on Coal Pillar Width and Support Design of Gob-Side Entry

Research on Coal Pillar Width and Support Design of Gob-Side Entry

Relationship between Critical Gap and Certain Geometrical Parameters in Roundabouts

Gap-acceptance method is one of the classical methods used to analyze capacity of roundabouts. Critical gap has a privileged role in this approach. Different driver behavior and local rules of traffic has a key role in implementing it in the local standard for capacity calculation in each country. Therefore, a reliable method for estimation of critical gap at a certain location can be of great importance. This paper presents the first steps of an experimental investigation and analysis on whether it is possible to find correlation between video-based gap acceptance data and certain design parameters of roundabouts in Hungary. Ten single lane roundabouts of different size were recorded for hours in different locations in and around Budapest to assess gap acceptance data and relate it to certain design parameters like diameter, distance of neighboring entries, entry width, width of splitter island, number of entries over time, and entry angle – or any combination of those. Using only a linear approach, strong positive correlation was found between measured critical gap and distance between legs. There is correlation (not so strong however) between critical gap and (approach) entry width as well as splitter island width, and enough data were examined to say that there is no correlation between central island diameter and critical gap.

Studying the effect of overburden removal flow diagram parameters on open pit possible productive capacity when developing an inclined formation

Introduction. The article discusses the technical and technological potential of coal mining economic efficiency enhancement for deposits formed by a formation of inclined beds using a combination of transport and transportless technologies. The considered reserve consists in the possibility of reducing the volume of overburden relocated by draglines and increasing the volume of prepared reserves by optimizing the excavation flow diagram parameters. The research was carried out for the Chernogorsky bituminous coal deposit of the Minusinks coal basin. Research objective is to reveal the regularities between changes in the deposit’s productive capacity for coal and the volume of overburden relocated on the one hand, and the parameters of flow diagrams that enhance the economic efficiency of a coal mining enterprise using the combination of transport and transportless technologies on the other hand. Methods of research. Process flow diagrams were analyzed, and the parameters of the entry width, the height of the overburden shotpile mined by the dragline and the height of the dragline elevation over the roof of bed were varied. The methods of graphical analysis were used based on the proposition about the equality of the width of the mining, stripping and dump panels and the areas of the dump and stripping entry ways. A regression analysis of the data obtained was carried out. Results. The regularities between the changes in the deposit’s productive capacity for coal and the volume of overburden relocated on the one hand, and the parameters of flow diagrams on the other hand, have been revealed. The need to control the open-pit’s productive capacity has been justified. The possibilities have been considered for production cost cut by reducing the scope of excavation. Summary. Flow diagram parameters optimization based on the identified regularities makes it possible to control the open-pit’s productive capacity and the volume of overburden relocated over a broad area. The height of the overburden shotpile mined by the dragline at Velikan 1 and Gigant 1 coal beds has the largest impact.

A Comparative Study of Flows Through Funnel-Shaped Bottlenecks Placed in the Middle and Corner

Upon exiting buildings, theatres, and stadiums, which house a great number of people, egress points can act as bottlenecks, resulting in crowded exits and decreased flows. Most studies investigating flow have been conducted in either narrow bottlenecks (doors) or funnel shape bottlenecks, with the latter investigating bottlenecks placed in the middle of the walkway. This study investigates, for the first time, crowd flow through funnel-shaped bottlenecks placed in the corner of the walkway and makes comparisons with similar bottlenecks of the same length, entrance and exit width placed in the middle of the walkway. The entry width and exit width of the bottlenecks were 3 m and 1 m respectively, with lengths varying from 1 m to 4 m; they continued into a 10 m corridor. Ninety-four participants of various ages were observed moving through each of the configurations. The results indicated that using funnel-shaped bottlenecks in the middle of the walkway increased the flow rate significantly compared to the corner in bottlenecks with 2 m and 3 m lengths. This is contrary to what some other researchers have found for narrow bottlenecks placed in the middle and corner of a wall, although it is recognised that the configuration of funnel-shaped bottlenecks makes the comparison more complex and further work is required in this area. Notwithstanding these results are considered valuable for consideration when designing egress points and corridors in complex buildings such as metro and train stations.

Investigation of the width of the entry of an excavator when loading a mobile crushing plant in the conditions of the Angren coal mine of Uzbekistan

This article presents the results of studies to establish the optimal entry width for an excavator working in conjunction with mobile crushing plants in the development of overburden of the Angren open pit. According to the results of the research, an analytical relationship was established to determine the maximum productivity of the mining system “excavator-mobile crushing-reloading-conveyor complex” with cyclical-flow technology. A structural diagram has been developed that allows you to select the type and determine the main technological parameters of the equipment with the selected criteria for evaluating the effectiveness of the complexes. It has been established that the choice of equipment for conveyor lines should be carried out taking into account the mutual influence of adjacent technological links of the central heating systems, including the influence of the excavator-crushing and crushing-conveyor complexes on the efficiency of their mutual functioning within the framework of the adopted system as a whole. A functional graphical dependence of the excavator performance on the face width was obtained, taking into account the relationship of all technological parameters of the face. It has been established that the maximum excavator productivity of 1478.1 m3/hr is achieved with an excavator entry width of 17.4 m for the conditions of the Angren open pit. The resulting schedule makes it possible to assess the possibility of increasing the operational performance of single-bucket shovel excavators under various conditions of work, as well as to continue the optimization of excavation.

.Research on the coal pillar width of gob-side entry retaining under the damage effect of heterogeneous rock

.Research on the coal pillar width of gob-side entry retaining under the damage effect of heterogeneous rock

Research on the Reasonable Coal Pillar Width and Surrounding Rock Supporting Optimization of Gob-Side Entry under Inclined Seam Condition

In order to study the optimal coal pillar width and surrounding rock control mechanism of gob-side entry under inclined seam condition, the 130205 return air entry adjacent to 130203 gob in Yangchangwan No. 1 well is taken as a typical engineering background. By means of engineering background analysis, theoretical analysis based on inside and outside stress field, numerical simulation by FLAC3D software, and in situ industrial test and relevant monitoring methods, the optimal coal pillar width and surrounding rock control technology are obtained. The results show that the influence range of inside stress field is about 12.2∼12.8 m based on theoretical calculation result; under the influence of 10 m coal column, the overall deformation of the roadway is relatively small and within the reasonable range of engineering construction, so the width of the coal pillar along the return air roadway is set to 10 m which is more reasonable; the cross-section characteristics of special-shaped roadway lead to asymmetric stress distribution and fragmentation of surrounding rock, and then the asymmetric surrounding rock control technology under the coupling effect of roof prestressed anchor + high-strength single anchor cable + truss anchor cable support is proposed. The monitoring results of this support method are effective for the maintenance of gob-side entry, and the study conclusions provide new guidance for the surrounding rock control mechanism of gob-side entry under inclined seam conditions.

Multi-Objective Evaluation Model of Single-Lane Roundabouts

Mobility, safety, and environmental sustainability are priorities in the geometric design of roundabouts. This paper presents a multi-objective optimization model that determines the geometric design elements of single-lane roundabouts using all three objectives. The user can specify weights for the objectives, or the model can determine the optimal weights. Mobility is defined in terms of roundabout delay and modeled using the United Kingdom empirical model. Safety is modeled in terms of collision frequency based on the methodology of the Highway Safety Manual. Environmental sustainability is represented by vehicle emissions (nitrogen oxides, hydrocarbons, carbon dioxide, and carbon monoxide) and is modeled using the vehicle-specific power methodology. The proposed model directly identifies the optimal geometric dimensions (decision variables) of the roundabout, including entry width, exit width, approach half-width, circulatory width, effective flare length, entry radius, entry angle, and inscribed circle diameter. The input data to the model include traffic data, site conditions, and limitations based on design guidelines. Application of the proposed model is illustrated using two actual roundabouts. The comparison results show that the proposed model provides substantial improvements in safety, mobility, and environmental sustainability compared with existing conditions. In addition, the model requires much less effort to apply compared with the traditional iterative method, and as such should be of interest to highway designers.

Analysis of Roof Failure at the Intersections on a Coal Mining

The objective of this paper is to understand the behavior of the roof and the cause of roof failure of a coal mining. Eleven roof falls occurred in the mine section in sequence. All the roof falls were surveyed, and the geological features were determined which include rock type, mechanical properties, and thickness. The immediate roof thickness was interpolated to determine the cause of the roof failures which was the inappropriate roof support where the immediate roof is thicker. The average thickness of the immediate roof was determined by the drilling log in 1.2 m (3.9 ft.). The roof support was design based on the average thickness, and the bolt length is 1.5 m (4.9 ft.) in suspension. The challenge was to estimate where the immediate roof gets thicker and to design the support considered to maintain the regular bolt length. This is because the cost and productivity of support operation could increase if the bolt length changes as the roof thickness changes. The idea was to adjust the support for beam building with a fully grouted bolt and rearrange the bolt geometry to keep the roof stable. It means, with the same bolt length the type of roof support would change from suspension to beam building depending on when the roof gets thicker. Two empirical approaches were considered to design the roof support: 1) CMRR and 2) RMR. The entry width is 5 m and the roof support was designed with four bolts per row. Where the roof support must change to beam building, the number of bolts per row changes to five or six. The results of the design and application on underground showed that the approach keeps stable.

Study on Coal Pillar Width and Surrounding Rock Control of Gob-Side Entry in Extra-thick Coal Seam

This paper adopts an integrated method of field test and numerical simulation to study coal pillar width and surrounding rock control of gob-side entry in extra-thick coal seam. Field test showed that when the coal pillar width was 30 m, the average plastic failure areas of the roof, coal pillar rib and virgin coal rib were 7.6 m, 4.9 and 3.8 m, respectively, and severe roof subsidence and large deformation of coal pillar rib occurred during the mining of the working face. A numerical model is established to study the change of plastic bearing zone and the distribution of stress and displacement under different pillar widths. The numerical results show that a coal pillar 8 m wide can meet the strength requirement of overlying load and puts the gob-side entry in a good stress environment. Finally, an optimal coal pillar width was estimated at 8 m and an effective support method was proposed. Drilling imaging data indicate that the newly designed pillar size and the proposed supporting method can ensure roadway stability. The proposed plastic bearing zone and zero-displacement plane are reliable indicators for designing pillar size. In addition, the new support strategy can be applied to other coal mines with similar geological conditions.

Comparison of Artificial Intelligence Based Roundabout Entry Capacity Models

This study focuses on the development of entry capacity models for roundabouts by using Genetic Algorithm (GA), Multi-variate Adaptive Regression spline (MARS) and Random Forest Regression (RFR) technique under heterogeneous traffic conditions. Required data were collected from 27 selected roundabouts of India by using high-definition video (HD) camera. Influence area for gap acceptance (INAGA) method is employed to find out the critical gap and follow up time. It is found from sensitivity analysis that variable like Entry width (Ew) contributes the most while the follow-up time (Tf) variable has less contribution in the proposed model.

How the laser beam energy distribution effect on laser surface transformation hardening process; Diode and Nd:YAG lasers

The laser surface transformation hardening (LSTH) of AISI 4130 steel by 1600 W high power diode laser (HPDL) and 700 W Nd:YAG lasers were investigated in this present study. The distribution influence, and the lasers beam shape; Top-hat in the HPDL and Gaussian distribution in the Nd:YAG laser, have been studied on the geometrical dimensions, and micro-hardness in hardened area (i.e.; depth, width, and angle of entry of hardened profile), micro-hardness deviation (MHD) from the row steel in geometric dimensions, and the ferrite’s percentage in hardened layer center. Microstructure evaluation of the laser hardened areas were performed by FE-SEM and optical microscopy. Based on the results, maximum hardness was created with the HPDL, and the geometrical dimension was more than the Nd:YAG laser. Also, MHD, and minor phase of ferrite in the HPDL laser surface hardening than the hardened layer in Nd:YAG laser, which is related to the higher laser absorption. Results show that, the hardened zone of HPDL is about 698 HV0.1 with 1.02 mm depth, while for Nd:YAG laser is about 698 HV0.1 with 0.98 mm depth. Comparing the results with the furnace hardening heat treatment (FHT) demonstrated that the hardness in diode laser and Nd:YAG laser hardening are 1.38 and 1.22 times of the hardness in FHT, respectively.

Developing crash modification factors for roundabouts using a cross-sectional method

Abstract The objective of the current study was to evaluate traffic and geometric features and their influences on the safety performance of roundabouts by developing suitable crash modification factors (CMFs). The cross-sectional method can be applied as an alternative method to estimate the CMFs when before-and-after studies are impractical to apply, e.g., lack of data from the period after implementing treatments. To accomplish the study objective, CMFs were derived from generalised linear models (GLMs), i.e., negative binomial (NB) regression, using data collected on regional roundabouts in Toowoomba City, Australia. Six years of crash data from 49 roundabouts included all recorded crashes as well as traffic and geometric features for the entire roundabouts. Several candidate models were developed using the GLMs. Five models were selected based on statistical significance, goodness-of-fit (GOF) measures, and cumulative residual (CURE) analysis. The results show that increasing the number of entry lanes, entry width, entry radius, traffic volume, circulatory roadway width, weaving width, and speed limit have positive effects on roundabout safety. On the other hand, increasing the number of legs, number of exit lanes, exit width, exit radius, weaving length, central island diameters, and presence of fixed object on a central island have negative effects on roundabout safety. The study shows that quantifying the risk factors can support road safety stakeholders to identify safety improvements at roundabouts more effectively and efficiently.

Stability Control for Gob-Side Entry Retaining with Supercritical Retained Entry Width in Thick Coal Seam Longwall Mining

Taking gob-side entry retaining with large mining height (GER-LMH) of the 4211 panel in the Liujiazhuang coal mine as the engineering background, a numerical simulation was conducted to study the surrounding rock deformation, stress, and plastic zone distribution of GER-LMH with respect to retained entry width. The concept of critical retained entry width of GER-LMH was proposed. In view of the deformation characteristics of surrounding rock, an innovative approach to determine the critical width of GER-LMH based on the cusp catastrophe theory was proposed. The cusp catastrophe functions were set up by approximate roadside backfill body rib convergence and roof subsidence series with respect to different retained entry widths. The critical retained entry width of GER-LMH was 4.0 m according to bifurcation set equations. Surrounding rock stability control principle and technique of GER-LMH was proposed, including “rib strengthening and roof control”: road-in support with high pre-stress rockbolts and anchor cables, roadside backfill body construction technology with high-water quick consolidated filling materials and counter-pulled rockbolt, road-in reinforced support technology with hydraulic prop support and roof master. Field test and field monitoring results show that GER-LMH with supercritical retained entry width in the 4211 panel could meet the requirements for ventilation when the 4211 panel was retreating.

The Development of Safety Performance Functions for Roundabouts in Amman, Jordan

It is now well established that crash occurrences at roadway segments or intersections are associated with a large variety of factors. Safety Performance Functions (SPF) are statistical models developed to predict crash frequencies for various design variables. In Jordan, almost half of all road crashes occur at intersections, mostly in urban areas. There is a significant number of roundabouts throughout Amman which is increasing without evaluating their safety performance. To assess safety benefits of this kind of intersections, transportation professionals need the powerful statistical tool; the SPF. This study aims to develop SPFs for roundabouts in Amman. The models consider the crash frequency, traffic volume and geometric features of all the studied 20 roundabouts. The developed SPFs were statistically significant (R^2 = 0.91) .The findings of the study revealed that crash frequency has a strong relation with the AADT, roundabout entry angle-degrees, entry path radius, splitter radius, pedestrian crossing structure, inscribed diameter, central diameter, circulating width, entry width, number of circle legs. The developed SPFs are evaluated through a comparison with others from developed countries.

Guidelines for roundabout circulatory and entry widths based on vehicle dynamics

Abstract Current guidelines for roundabout circulatory roadway width are based on a static method that does not consider circulatory speed. In addition, the roundabout entry width is based on practical experience. This paper presents a method for determining the circulatory and entry widths based on a two-dimensional vehicle dynamics model that involves a system of differential equations of curvilinear motion. The method considers the interactions between a vehicle and road geometric elements, including tire sideslip, vehicle weight, vehicle speed, and vehicle stability. Three design vehicles are considered: intermediate semitrailer (WB-12), interstate semitrailer (WB-20), and city transit bus (CITY-BUS). Design guidelines for the required circulatory width are established for different circulatory speeds (0–60 km/h) and different inscribed circle diameters (30–80 m). To simplify the guidelines, for each design vehicle and for each inscribed circle diameter (ICD) the regression model of circulatory roadway width as a power function of circulatory speed was fitted. Guidelines for entry width were also established for typical conditions. The results show the efficiency of the proposed method which provides smaller values of circulatory roadway widths than those of current methods. The difference ranges from 0.4 to 0.6 m for CITY-BUS, 0.7–1.0 m for WB-12, and 1.3–2.0 m for WB-20. The proposed guidelines would be useful in case of spatial restrictions.

Probability and reliability analysis of pillar stability in South Africa

A deterministic approach is frequently used in engineering design. In this quantitative design methodology, a safety factor, which is typically a strength-to-stress ratio, is derived as an index for the stability assessment of the engineering design. In underground coal mining applications such as pillar design, however, the inputs of pillar design are variables. This is widely overlooked in the deterministic approach. A probabilistic approach assessing the probability of failure or reliability of a system might be an alternative to the conventional quantitative methodology. This approach can incorporate the degree of uncertainty and deviations of variables and provide more versatile and reliable results. In this research, the reliability of case histories from stable and failed pillars of South Africa presented by Merwe and Mathey is examed. The updated Salamon and Munro strength formula (S-M formula) and Merwe and Mathey strength formula (M-M formula) are evaluated through a probabilistic approach. It is concluded that stable pillar cases have a reliability value greater than 0.83 while the reliability value of failed pillar cases are slightly larger than 0.50. There seems to be a positive relation between safety factor and reliability. The reliability of a pillar increases with pillar width but decreases with depth of cover, pillar height and entry width. The reliability analysis also confirms that M-M strength formula has a better distinction between the stable and failed pillar cases.

Design of a rotary for an uncontrolled multi-leg intersection in Chennai, India

One way to control the traffic at busy intersections is to construct a roundabout or rotary intersection, which is a special type of at-grade intersection, where all converging vehicles are forced to move round a central island in clock-wise direction. The present study aims to design a rotary for an uncontrolled multi leg intersection located in Royapetah in Chennai, India. The intersection has five approach roads with two-way traffic in all the approach roads and there is no signal or traffic police to control the traffic at present and hence experiences traffic chaos during peak hours. In order to design the rotary, it is essential to have the information on traffic volumes coming from the approach roads. For this, a video data collection was carried out for a duration of eight hours from 7.30 am to 11.30 am and from 2.30 pm to 6.30 pm on a typical working day using a handycam from the terrace of an apartment building located near the intersection. During data extraction stage, each 5 min. traffic volume was extracted for all the five classes of vehicles considered and were converted to passenger car units (PCU). The analysis of traffic data showed that during peak hour from 4.45 pm to 5.45 pm, the proportion of weaving traffic, i.e., ratio of sum of crossing streams to the total traffic on the weaving section was found to be 0.81. According to Indian road congress (IRC) guidelines, this proportion can take any value between 0.4 and 1 and in the present study, the calculated value is found to be within the prescribed range. Using the calculated values of average entry width of the rotary and width & length of weaving section, the practical capacity of the rotary was found to be 3020 PCUs which is well above the observed traffic volume of 2665 PCUs.