建筑物下采煤新模式似膏体充填技术外文文献翻译

A New Mode of Coal Mining Under Buildings with Paste-Like Backfill TechnologyCUIJian-qiang(崔建强),SUNHeng-hu(孙恒虎),HUANG Yu-cheng(黄玉诚)(School of Resources and Safety Engineering,CUMT, Beijing 100083, China)Abstract:The formation of the paste-like backfill technology was introduced briefly in this paper. From the actual cases of coal mines, a new mode of coal mining under buildings with the technology was proposed. And its specificity was analyzed, and a further introduction to the full-sand-soil solidifying material was given. The main parts of the backfill system, such as the backfill preparation system, the pipeline transportation system,the backfill systems in fully-mechanized mining faces and the backfill process, were presented emphatically.Keywords:mining under buildings; paste-like backfill; full-sand-soil solidifying material1IntroductionWith the rapid increase of the demand of social and economic development, the conflict between coal shortage and economic development is becoming more and more conspicuous. More attention has been paid on coal mining technology under buildings. The present coal mining technology under buildings can not be widely applied for its some shortages, such as the poor effect of surface subsidence and deformation controlling, the serious pollution of underground operation environment and the low recovery of resources. Paste-like backfill technology has outstanding advantages, such as the wide supply of backfill materials, the low cost of backfilling, the easy preparation of slurry and the high strength of backfill body. It can control surface subsidence and deformation effectively, gain a high recovery, and does not pollute underground operation environment. Using the new mode, harmless and non-pollution mining under buildings can be realized.2Proposal and Specificity of the New ModeIn all the modes of coal mining under buildings backfill mining is the most effective in the control of surface subsidence and deformation and the recovery of coal. The density of backfill body and its subsidence contraction influence the movement and deformation of surface and surrounding rock directly. The solidifying backfill mining technology has been widely applied in royal and nonferrous mines, for its backfill body has the following advantages such as high density, little subsidence contraction, and enough strength and stiffness. With the development of modern science and technology, the solidifying backfill mining technology has been improved and developed greatly. Based on the development trend of solidifying backfill technology, Professor SUNHeng-hu proposed a new mode referred to as pastelike solidifying backfill. The new modes specificity is that it has not only the advantages of both hydraulic backfill and paste backfill, such as the good slurry fluidity and the easy pipeline gravity transportation for the former, and the great backfill body strength and the non-or little dehydrating for the later.The traditional binder cement has the poor capability of fine particlessolidifying. When the density of backfill slurry is lower than that of paste, the slurry is easy to transport through pipelines by gravity, which will result in the loss of fine particles (including cement particles) in the dehydrating process. So the subsidence contraction of its backfill body increases and the strength decreases, which leads to the loss of binder and the serious pollution of underground operation sites. When the density of backfill slurry is close to that of paste, its fluidity becomes poor and difficult to transport. Therefore,the key to the realization of paste-like backfill mode is to research and develop a new kind of binder. It is necessary for this binder to have the capability of solidifying fine particles and for its backfill body to meet the need of strength. Meanwhile, it must have a wide range of backfill materials and a lower backfill cost.The research group leaded by Professor SUNHeng-hu has developed a new generation binder,full-sand-soil solidifying material. With the new solidifying material, the paste-like backfill mode is forming gradually, which absorbs the advantages of the modern solidifying backfill and spurns its disadvantages.Based on the knowledge of solidifying backfill engineering practice, the actual situation of coal mines and the paste-like backfill technology, a new mode of coal mining under buildings is set up. So this new mode and its system design have both something similar to the solidifying backfill technology in metal mines and its own characteristics. Backfill material: The newly developed full-sand-soil material is adopted as binder, and debris (waste from coal mines) and fly-ash (waste from steam electric plants) are used as aggregate. Backfill area: Coal deposits takes the shape of seams, most of which have a low angle, so the area to backfill is great and backfill slurry have to be transported farther. Compared with metal deposits normally taking the shape of block or vein, the ratio of total length to height difference is larger. Backfill capacity: Generally, fully-mechanized working faces in a coal mine has a larger productivity than a metal mine. So, a larger backfill capacity of the backfill system is needed. Selection of backfill preparation station sites: The backfill system must meet the demand of the ratio of total length to height difference of paste-like slurry transportation. Moreover, the transportation of backfill materials on the earths surface must be taken into account so as to lower the backfill cost farthest, for the backfill amount is great. Coordination: To assure the production of fully-mechanized working faces and the quality of backfill body, the processes of mining and backfill must be coordinated well. By now, there is no relative engineering experience.3 The New Mining Mode Under Buildings and Its System Layout3.1Full-sand-soil solidifying materialThe full-sand-soil solidifying material is a kind of powder made of some industrial waste, such as blasting-furnace slag, smelter slag, and proper portion of natural minerals and chemical catalysts through milling and mixing. It has a powerful capability of solidifying sandy soil and industrial waste (such as tailings) containing a high percentage of clay. Hence comes its name full-sand-soil solidifying material, called full-sand-soil material for short.Compared with Portland cement, the full-sand-soil material has its own specificity in the respects of technological property, production process and engineering applications. It has a super quality of solidifying fine particles. Under the condition of equal dosage, its strength is 23 times that of cement. Under the same strength demand, its dosage is less than half that of cement. Compared with regular cement, its early strength is high, and 7-days strength and 28-days strength can reach that of 425#and 525#cement standards, respectively. The process of producing the full-sand-soil material is to “engulf”a large amount of industrial waste, and to produce super binder with good property and wide uses at a low price. Its production cost is low, approximately 200 yuan per ton. Therefor, the full-sand-soil material will not only find wide applications in mining, communication, construction, water conservancy and oil projects, but carve out a completely new way to reutilize industrial waste.3.2The system layout of paste-like backfill mining under buildings3.2.1Backfill preparation station system Location selectionDistinguished from paste backfill, one of the specificity of the paste-like backfill is that the fluidity of its slurry is excellent. Without or with a little transportation pressure, its slurry can be transported to backfill sites. For this reason, when the location of a backfill preparation station is selected, the demand for the ratio of total length to height difference should be met firstly so that the paste-like backfill slurry flow by gravity can be ensured. Secondly, the transportation work of a backfill materials on the earths surface should be minimized furthest. The capacity of a backfill preparation station should be about 2.0 times that of the backfill mining face. Since a coal face usually has a large productivity per year, so lowering the backfill material transportation cost will be of outstanding sense. Layout of a backfill preparation stationBased on the capacity of a backfill preparation station, the specificity of backfill materials and the practical experience of solidifying backfill mining in metal mines, it is more suitable for a backfill preparation station to adopt a two-step mixing system, i.e., the first-step mixing drum prepares mortar,made from debris, fly-ash and water, with a density about 73%; and the two second-step mixing drum prepares paste-like backfill slurry with a density about 75% made from the full-sand-soil material and the mortar produced by the first-step mixing drum.To ensure the reliable operation of a backfill preparation station, two mixing drums are set for each step. When one of the two first-step mixing drums is working normally, the other is alternate. Both of the two second-step mixing drums are working normally at the same time. When something is wrong with one of the second-step mixing drums,the other can produce backfill slurry by itself. The advantage of the layout is that when one of the mixing drums has something wrong, the production of slurry does not be influenced so as to ensure the continuity of the backfill process.3.2.2The pipeline transportation system of paste-like backfill slurryFirstly, the layout of the pipeline transportation system must meet the demand for the backfill capacity and make the backfill operation be high quality, efficient, safe and economic. It is not permitted for the backfill pipeline to be laid upward.Meanwhile too many turns should be avoided so as not to result in the natural pressure loss of backfill slurry and pipeline blocking. The pipeline to underground should be laid in the auxiliary shaft or air shaft as far as possible. Utilizing the existent shafts,roadways and ground installation can decrease the backfill pipeline laying cost and also make the pipeline conveniently inspected and repaired. The backfill pipeline layout in a coal mine can be seen in Fig.1. Its backfill pipeline is laid through a backfill bore-hole, auxiliary shaft, main entry, return dip,tail-entry to the backfill site.Fig.1Backfill pipeline layout at the beginning period1.Backfill preparation station; 2.Town buildings;3.No.6 shaft;4.Filling pipe;5.Entry at-570m level;6.Entry at-710m level;7.Return dip;8.Transportation dip;9.Tail-entry;10.Fully-mechanized mining face;11.Head-entryFrom the pipeline layout in Fig.1, the actual ratio of total length to height difference can be calculated by the following formula: N=L/H,Where N is the ratio of total length to height difference,L is length of the backfill pipeline,L=|AB|+|BC|+|CD|+|DE|+|EF| in m, and H stands for the height difference between the slurry entrance on the earths surface and the slurry exit at the underground backfill site,H= the height of point A- the height of point F in m.On the basis of the laboratory research on the paste-like slurry flow specificity and the similar engineering experience of metal mines,N=3-6 is the most suitable value for the paste-like slurry to be transported through a pipeline by natural pressure.3.2.3Backfill system in fully-mechanized working facesThe gob resulted from backfill mining is filled with backfill materials tightly. In the process of deformation with surrounding rock, the backfill body with certain strength and stiffness increases the capacity of surrounding rock effectively and gives some load-bearing capacity towards roof strata gradually. A reasonable roof-controlling area can be obtained from a site test and the strata control theory so as to ensure the safety of backfill operation. Thus along the working face a row of hydraulic props should be set in the gob behind powered supports. The distances between hydraulic props and between hydraulic prop row and powered supports, and the width of each backfill strip can be obtained through numerical simulation and in situ tests on the basis of roof stability, mining depth, tectonic stress and so on.Thus, a backfill road is formed between hydraulic props and powered supports. Flexible shuttering is set up along a side of the gob against hydraulic props to support backfill slurry and filter water. Its layout can be seen in Fig.2.The backfill systems advantages are that mining and backfill processes are independent of each other, its large filtering area is good for the increasing backfill bodysearly strength, and the filtered water can flow to the head-entry directly and not result in polluting of the working face.Fig.2Backfill pipeline layout at the begining period1.Head-entry; 2.Tail-entry;3.Powered support;4.Hydraulic prop;5.Flexible shuttering;6.Backfill road;7.Preparatory backfill strip;8.Complete backfill strip3.2.4The process of backfill technology Preparation processThe preparation process of backfilling includes sealing of the flexible shuttering, linking of the backfill pipes, communicating between the backfill site and the backfill preparation station, cleaning up of the head-entry drainage ditch and so on. Backfill processWhen the preparation operation is accomplished, the backfill preparation station begins the backfill operation. Firstly, the backfill pipes is washed by using clean water and the pipeline is inspected to determine whether it leaks or not. If all is OK, then slurry is transported down through the pipeline. In order to prevent the washing water from flowing into the gob, a valve should be set up before the pipeline is laid to the backfill site. By this way, the clean water resulted from the pipeline washing may be drained to the head-entry ditch directly.Backfill workers operate at the T junction of the tail-entry when backfill begins. Attention should be paid intently on backfill operation. When abnormal cases occur, relative measures should be taken at once.While the gob is being filled with slurry during the backfill period, little water can be dehydrated from the seams or the flexible shuttering and is drained to the head-entry, which prevents it from flowing to the working face and causing pollution to the operation environment.Closing processWhen backfill slurry reaches at the predetermined position, the backfill preparation station stops producing slurry. To prevent the backfill slurry from detaining and solidifying in the pipes to block the filling pipe or make its radius decrease, the backfill pipeline is washed using clean water for a further use when there is no slurry flowing out at the end of the backfill pipeline.4The Estimation of Surface SubsidenceProbability integration is the traditional method to estimate surface subsidence resulted from coal mining under buildings. Take the feasibility research on one coal mines paste-like backfill mining under buildings as an example. The calculation scope is the full subsidence area. Based on the mining areas empirical values of the parameters for the probability integration, surface subsidence is estimated.Its mining depths are 971, 1241 and 701 m in trend direction of the main section, at the lower boundary and at the upper boundary, respectively.The seam thickness, including 5 coal seams, is 10.6m, and the average seam dip is 21. According to the relevant literatures on solidifying backfill technology, subsidence coefficient q=0.020.05, tangent of the main influence angle, taken by medium stable strata, tan=1.7 and horizontal moving coefficient b=0.3. The calculation results are listed in Table 1.Table1 The estimation of surface subsidence induced paste-like backfill mining under buildings in a coal mineCalculationsectionMax subsidenceW/mmMax dippingi/(mmm-1）Max curvatureK/(10-3m-1）Max horizontalMovement U/mmMax horizontaldeformation/(mmm-1)Main section in the trend direction1984950.350.870.0090.0023591480.160.40Main section in the rise direction1984950.270.680.00060.0014591490.120.31Main section in the dip direction1984950.421.060.00140.0034511290.170.42From Table 1, both surface movement and deformation values are smaller than the deformation standards of No.1 protection regulation for masonry structure buildings in China, that is, max dipping coefficient i3.0mm/m, max curvature K0.210-3/m, max horizontal deformation2.0mm/m.5ConclusionsBased on the existent backfill modes and the trend of modern backfill development, a new backfill mode, paste-like backfill technology, is put forward. Its binder has good quality and low price, and it can also reutilize a large amount of industrial waste. These advantages will make the backfill cost decrease greatly. Consequently, the paste-like backfill mode will carve out a new way for coal mining under buildings. With the paste-like backfill technology, the new mode of coal mining under buildings will certainly find application in solving the environment pollution resulted from debris and fly ash, and recover a large amount of coal under buildings. Therefore, to the sustainable development of Chinese coal mining, the new mode will have a great and far-reaching strategy meaning.建筑物下采煤新模式似膏体充填技术崔建强，孙恒虎，黄玉诚（中国矿业大学（北京） 资源与安全工程学院 北京 100083）摘要：本文简要的介绍似膏体充填技术的形成。从煤矿的具体实际出发，提出了建筑物下煤炭开采的一种新技术。并且分析了这种技术的特殊性，进一步介绍了全沙土壤固化材料。重点提出了充填系统的主要部分，如充填准备系统，管道运输系统，综采充填系统的工作面和充填工艺过程。关键词：建筑物下采煤；似膏体充填；全沙土壤固化材料1 引言随着社会和经济发展的需求迅速增加，煤炭短缺与经济发展的矛盾变得越来越突出。建筑物下采煤技术更受到人们的重视。目前的建筑物下煤炭开采技术由于它的一些不足不能被广泛应用，如控制地面沉降和变形效果差，井下作业的环境污染严重和资源回收率低。似膏体充填技术优势突出，如充填材料供应广泛，充