大采高工作面采场支承压力分布规律分析

以寺河矿大采高高效回采工作面为试验对象,采用超前支柱监测、回采巷道及留巷变形监测、煤体应力监测等技术手段,研究分析了该工作面采场支承压力分布规律及巷道变形特征,为工作面巷道布置、采场及巷道围岩控制等提供依据.研究结果表明,与常规大采高工作面相比,该工作面超前支承压力的影响范围为9～15m,集中系数为1.7～1.9,峰值位置前移,位于煤壁前方12m处;后方支承压力具有明显的分区特征并伴有一定的滞后性;侧向支承压力峰值位置变化不大.

Application of excavation compensation method for enhancing stability and efficiency in shallow large-span rock tunnels

Engineering shallow,large-span rock tunnels challenges deformation control and escalates construction costs.This study investigates the excavation compensation method(ECM)and its associated technologies to address these issues.Utilizing five key technologies,the ECM effectively modulates radial stress post-excavation,redistributes stress in the surrounding rock,and eliminates tensile stress at the excavation face.Pre-tensioning measures further enhance the rock’s residual strength,establishing a new stability equilibrium.Field tests corroborate the method’s effectiveness,demonstrating a crown settlement reduction of 3–8 mm,a nearly 50%decrease compared to conventional construction approaches.Additionally,material consumption and construction duration were reduced by approximately 30%–35%and 1.75 months per 100 m,respectively.Thus,the ECM represents a significant innovation in enhancing the stability and construction efficiency of large-span rock tunnels,marking a novel contribution to the engineering field.

采场支承压力全程动态演化特征及机理分析

为促进工作面及巷道围岩稳定性控制,利用应力监测装置对不同矿区采场支承压力进行了连续监测,总结了采场支承压力全程动态演化特征,分析了不同演化特征的机理。结果表明:采场超前支承压力的传递呈现“工作面中部向两端头扩展”的动态迁移特性,在工作面中部区域,应力的传递沿倾向方向具有同步性及均衡性,沿走向具有差异性及不均衡性,应力增量呈“工作面中部区域>临空侧>实体煤侧”的区域差异性。采场不同区域覆岩破断的时序性是超前支承压力动态迁移特性的根本原因,中部区域破断岩块同步整体回转的特性决定了应力传递的同步性及均衡性,岩块破断步距、回转角度的差别决定了应力传递的差异性及不均衡性,覆岩破断块度、空间位置决定了应力增量的区域差异性。采场侧向支承压力演化存在“单峰起伏”和“双峰起伏”两种形式,单峰状态下采空区侧向顶板处于长期悬顶状态,双峰状态下侧向顶板依次经历了破断、回转失稳及再稳定过程。工作面煤柱较宽时,双巷掘进、单侧工作面采动下,侧向支承压力呈“双承载点同步传递”的状态,侧向顶板偏载应力、煤柱内刚度区域差异化是双承载点同步传递的原因。该研究结论对工作面回撤通道支护、煤柱宽度优化的确定具有重要参考意义。

“采充并行”式保水采煤方法

针对目前充填保水采煤方法存在的充填时间和充填空间不足,采煤与充填作业协调困难等问题,提出"采充并行"式充填保水采煤方法。在开采过程中,首先将整个开采块段内的所有采场支巷划分为多个开采阶段,每当开采并充填完一个阶段内的所有采场支巷后,再进行下一阶段采场支巷的开采和充填,直至开采和充填完所有采场支巷,最终实现充填体与煤炭的完全置换。为有效控制覆岩移动,每个采场支巷开采完毕后就立即对其进行充填。为确保正在开采的采场支巷两帮是实体煤或已达到设计强度的充填体,在阶段内对采场支巷进行间隔开采。研究成果应用于王台铺煤矿,在块段内煤炭资源采出率达96.8%的条件下,实现了浅表水资源的保护,地表变形量也小于建筑物Ⅰ级损坏等级指标。该方法采用一采一充一备的"采充并行"式充填开采模式,充分发挥快速连采和充填采煤的优点,可实现保水采煤。

Single Bubble Behavior in Direct Current Electric Field

The investigation on bubble behavior in electric field helps to analyze the mechanism of electric enhancement of boiling heat transfer. Experiments were performed to investigate the bubble deformation in direct current （DC） electric field with bubbles attached to the orifice. The air bubbles were slowly generated in the transformer oil pool at different orifices, so that the effect of flow on bubble shape was eliminated. The results showed that the bubbles were elongated and the departure volume decreased when the electric field was intensified. The major and minor axes, aspect ratio and departure volume increased with increasing the orifice diameter. Both the electric field and orifice size have great influence on bubble behavior. The bubble deformation was also simulated to compare with the experimental results. The numerical and experimental data qualitatively agree with each other.

Side abutment pressure distribution by field measurement

Given the 7123 working face in the Qidong Coal Mine of the Wanbei Mining Group, nine dynamic roof monitors were installed in the crossheading to measure the amount and velocity of roof convergence in different positions and at different times and three steel bored stress sensors were installed in the return airway to measure rock stress at depth. On the basis of this arrange- ment, the rule of change of the distribution of the side abutment pressure with the advance of the working face and movement of overlying strata was studied. The rule of change and the stability of rock stress at depth were measured. Secondly, the affected area and stability time of the side abutment pressure were also studied. The results show that: 1) During working, the face advanced distance was from 157 m to 99 m, the process was not effected by mining induced pressure. When the distance was 82 m, the posi- tion of peak stress was 5 m away from the coal wall. When the distance was 37 m, the position of peak stress away from the coal wall was about 15 m to 20 m and finally reached a steady state; 2) the time and the range of the peak of side rock pressure obtained from stress sensors were consistent with the results from the dynamic roof monitors; 3) the position of the peak pressure was 25 m away from the coal wall.

Characteristics of ground behavior of fully mechanized caving faces in hard thick seams

It is showed in practice that the support load and its fluctuation is large, the periodic weighting is obvious and can be divided into two kinds, the large and small pressure, sometimes the behavior of the large pressure is very violent in hard thick seam caving faces. These are obviously different from those of the generally soft or medium hard seam caving feces. All above these are summarized, and the causes aroused these are researched. Finally the powered support selection of hard thick seam caving faces is discussed.

Classification of underwater still objects based on multi-field features and SVM

A Support Vector Machine is used as a classifier to the automatic detection and recognition of underwater still objects. Discrimination between the objects can be transferred into different projection spaces by the process of multi-field feature extraction. The multi-field feature vector includes time-domain, spectral, time-frequency distribution and bi-spectral features. Underwater target recognition can be considered as a problem of small sample recognition. SVM algorithm is appropriate to this kind of problems because of its outstanding generalizability. The SVM is contrasted with a Gaussian classifier and a k-nearest classifier in some experiments using real data of lake or sea trial. The experimental results indicate that SVM is better than the others two.

Sensor monitoring of a newly designed foundation pit supporting structure

A new type of pit supporting structure, which was tested and verified using the sensor monitoring technology, was presented. The new supporting structure is assembled by prefabricated steel structural units. The adjacent steel structural units are jointed with fasteners, and each steel structural unit has a certain radian and is welded by two steel tubes and one piece of steel disc. In order to test and verify the reliability of the new supporting structure, the field tests are designed. The main monitoring programs include the hoop stress of supporting structure, lateral earth pressure, and soil deformation. The monitoring data of the field tests show that the new supporting structure is convenient, reliable and safe.

Analysis on the driving forces of different airports and routes

There has been a great deal of research on the driving force of aviation network.Moreover, the research methods and perspectives are also varied.This article mainly studies the driving force of aviation network,the influencing factors of main driving force are analyzed.The driving force analysis of different airport and route is carried out respectively.The results can better reveal the connection mechanism of solid routes.Because the sample space of the hub airport and the trunk airport is too small,the conclusions are not sufficiently illustrative,therefore, this article studies only the branch airports.The conclusions are compared with the results of the comprehensive analysis,and we see if the conclusions are the same or similar.

Arrival Pattern Recognition and Prediction Based on Machine Learning

A data-driven method for arrival pattern recognition and prediction is proposed to provide air traffic controllers(ATCOs)with decision support. For arrival pattern recognition,a clustering-based method is proposed to cluster arrival patterns by control intentions. For arrival pattern prediction,two predictors are trained to estimate the most possible command issued by the ATCOs in a particular traffic situation. Training the arrival pattern predictor could be regarded as building an ATCOs simulator. The simulator can assign an appropriate arrival pattern for each arrival aircraft,just like real ATCOs do. Therefore,the simulator is considered to be able to provide effective advice for part of the work of ATCOs. Finally,a case study is carried out and demonstrates that the convolutional neural network(CNN)-based predictor performs better than the radom forest(RF)-based one.

Similarity simulation of bolt support in a coal roadway in a tectonic stress field

In order to study the mechanism of bolt support and the behavior of strata in a coal roadway under tectonic stress,deformation and destruction of a roof,floor and sides were studied using an experiment in similarity simulation.We also studied the mechanism and types of bolt support functions in the coal roadway.The results show that with an increase in horizontal tectonic stress,the strata in the roof and floor of the roadway gradually separate and become shear failure areas.Coal in side walls moves,but its integrity remains intact.Side bolts are mainly affected by tension and roof bolts by the effect of shear.

Spontaneous caving and gob-side entry retaining of thin seam with large inclined angle

Based on the research method of combining simulation analysis with field testing by distinct element process UDEC, we have analyzed the roof deformation and failure laws and roadway support technology of gob-side entry retaining in a thin seam with a large inclined angle. The results show that during exploitation in seams with large inclined angle, rotational subsidence of the main roof under the gob area is small and can maintain balance, so there is no need to provide artificial permanent support resistance for the main roof near the upper side to control rotational subsidence. Obstructed by the dense scrap rail,waste rock from the immediate roof caving slides from the upper gob area to the lower area and fills it,which strikes a balance between the immediate roof under the goaf after it fractures into large pieces and filling waste rocks.

Discovering Niche Market： Consumer Preferences and Willingness to Pay for Organic Pork

With the concern for environmental quality and food safety, organic food products are becoming more important in the global market. In recent years the organic food industry has been expanding and sales of organic products have been increasing. Abundant studies have been done focusing on organic fruits and vegetables which focused on the shortage of organic live stocks. In this paper we focus our attention on organic pork products. Using a sample of 400 Thais consumers, this study proposes the contingent valuation （CV） technique to measure the willingness of individuals to pay a price premium for organic pork in Thailand. In order to obtain the mean ＂willingness to pay＂ （WTP）, a bivariate probit model was applied to provide information about the crucial variables that affect the WTP. The study revealed that variables that better approximate WTP are based on the lifestyle and knowledge about organic foods rather than the usual socioeconomic factors. The mean WTP on the premium price for organic pork is approximately 34.30 Bath per kg. In order to access the market potential this study shows that the suitable attributes of organic pork which is consistent with consumer preferences are composed of modernized and environmental packaging with special product details. Marketing this product to the buyer it should be set at a reasonable price. Stimulating the market should be done by doing sales promotion and public relations on a regularly basis. In addition, organic pork should be available in any places and convenient for customers to buy.

采场支承压力分布及发展规律的研究

采场周围煤体上的支承压力主要来源于受采动影响上方已经产生运动的岩层。在传统开采条件下,老塘冒落的矸石对上覆岩层的支承作用很小,运动岩层的重量主要由工作面四周煤体支承。煤体在高集中程度支承压力的作用下,容易发生冲击地压等灾害。

Support pressure assessment for deep buried railway tunnels using BQ-index

Estimation of support pressure is extremely important to the support system design and the construction safety of tunnels.At present,there are many methods for the estimation of support pressure based on different rock mass classification systems,such as Q system,GSI system and RMR system.However,various rock mass classification systems are based on different tunnel geologic conditions in various regions.Therefore,each rock mass classification system has a certain regionality.In China,the BQ-Inex(BQ system)has been widely used in the field of rock engineering ever since its development.Unfortunately,there is still no estimation method of support pressure with BQ-index as parameters.Based on the field test data from 54 tunnels in China,a new empirical method considering BQ-Inex,tunnel span and rock weight is proposed to estimate the support pressure using multiple nonlinear regression analysis methods.And then the significance and necessity of support pressure estimation method for the safety of tunnel construction in China is explained through the comparison and analysis with the existing internationally widely used support pressure estimation methods of RMR system,Q system and GSI system.Finally,the empirical method of estimating the support pressure based on BQ-index was applied to designing the support system in the China’s high-speed railway tunnel—Zhengwan high-speed railway and the rationality of this method has been verified through the data of field test.

Carbon Accumulation in a Humid Temperate Prairie Pasture Following Abandonment and Afforestation

Carbon budget changes were measured on a farm near Robinson, Texas, where land originally tilled for hay production was abandoned over time periods of 10, 20, and 35 years followed by succession of prairie and forest vegetation. Woody biomass accumulation increased following abandonment from 0.14 kg C m2 yr~ during forest initiation to 0.57 kg C m2 yr-1 of the mature forest Soil carbon was highest in the tilled field （ 15.77 kg C m2） with lowest in the grassland （ 11.66 kg C m-2）. Soil nitrogen was highest in the tilled field （0.55 kg N ms） and lowest in the forest transition （0.38 kg N m2）. Soil C：N ratios were highest in the forest transition （C：N=36） and lowest in the grassland （C：N=22）. Soil respiration was constant across the site with an annual average value of 1.46 kg CO2-C m-2 yr-. Results show that land in this region may be a source of carbon for several decades following abandonment due to enhanced soil carbon emissions as a function of nutrient input shifts.

The Successful Methodology for Enterprise Resource Planning （ERP） Implementation

Organizations need to use a proved methodology to reduce implementation risks and enable the enterprise resource planning （ERP） solution to be put into operation as quickly as possible. The right implementation methodology will also help ensure that the ERP implementation fully addresses an organization＇s business goals and objectives. Modern ERP implementation methodology encourages and supports a progressive approach to the management for users of ERP systems. A company is constantly seeking better methods and models for decision supports in all kinds of decisions and developing/copying new products/markets that generate the growth of the company. On the other hand, a company creates efficient and effective operations that improve the return on investment, because ERP is always considered as an asset. This paper focuses on the interaction of culture in a company, business strategy, and organizational skills and balances the relationship among ERP methodology, ERP implementation, and the performance of the company. Considering the fact that different ERP systems use different methodologies, short descriptions of the most dominant brand name ERP are analyzed （Oracle Financials, PeopleSoft, and systems, applications, and products （SAP） implementation methodology）. Although all methodologies may look similar, the selection of a proper methodology is the most critical part in ERP investment. The focus of this paper is on the accelerated SAP methodology, also named as ASAP methodology, because it is the most used one on the worldwide market of ERP systems.

The Theory of Internet Finance

Internet based technologies, such as mobile payments, social networks, search engines and cloud computation, will lead to a paradigm shift in financial sector. Beside indirect financing via commercial banks and direct financing through security markets, a third way to conduct financial activities will emerge, which we call ＂internet finance＇＂ This paper presents a detailed analysis of payment, information processing and resource allocation under internet finance.

Stock selection using support vector machine in Chinese securities exchange

The risk and performance of ST stocks are studied.The SVM method is applied on 100 general stocks and 100 ST stocks selected from the website,and a criterion is gotten to select stocks,then the risk of these sample stocks is analysed.In the performance evaluation,the SVM method is also applied on the 100 general stocks and 100 ST stocks according to the return per share,and 57 stocks which are all +1 are selected.Their equally weighted return rate is only-0.02%,but equally weighted return rate of 31 general stocks is 13.23%,that of 26 ST stocks is-96.15%.Naturally,we conclude that ST stocks are unsteady and do not deserve long-term investment.From the Chinese fund website,we know that equally weighted return rate of stock fund in 2004 was-3.3%,so the equally weighted return rate of the selected stocks(except ST stocks)is much higher than that of average return rate.