發(fā)布時間：2018-10-12 17:42

【摘要】：煤層卸壓開采是通過應力釋放使煤體產生大量的新生裂隙，改變煤體結構特征，促使煤層滲透性發(fā)生了根本性的改變，實現(xiàn)煤層增透以促瓦斯抽采。本文以煤層卸壓開采為主線，以載荷煤體滲透率演化特性和煤體裂隙擴展機制為重點，以理論分析、實驗研究、數(shù)值模擬和工程實踐為主要手段，研究加卸荷過程中煤體裂隙演化和滲透率變化過程，獲得滲透率演化規(guī)律和建立相應模型，并將結果應用于卸壓開采下被保護層滲透率的分布特性和卸壓瓦斯抽采的研究。本論文的主要研究結論如下： （1）制取標準原煤樣，采用與卸壓開采煤層受力特征相同的力學路徑，進行了不同加卸荷下的滲透率實驗，得到了不同層理方向上滲透率比達7.5：1，分析卸荷過程滲透率演化差異原因，提出在相同卸荷點應力下試樣初始損傷程度越大，卸荷極限承載強度就越低，致使在卸荷過程中試樣損傷變形的加劇和大量新裂隙的產生，，最終滲透率劇增且大于加荷過程的滲透率。根據(jù)滲透實驗結果獲得了卸荷增透的實驗現(xiàn)象和新認識。 （2）將損傷力學、卸荷力學和滲流力學相結合，運用RFPA2D Flow軟件模擬了加卸荷作用下不同預置層理試件裂隙起裂、擴展、貫通機制和滲透特性，獲得載荷條件下試件裂隙演化過程和滲透變化規(guī)律，滲透率的變化與裂隙演化具有一致性。并與滲透實驗對比分析，指出卸荷點處試件內部出現(xiàn)的破壞點和損傷微裂隙越多，在卸荷后微裂隙擴展速度就越快，破壞點數(shù)量則更多，最終易產發(fā)生破斷變形，滲透率劇增。 （3）根據(jù)在載荷條件下試樣滲透實驗和裂隙演化模擬，得出加荷過程試樣滲透率隨著有效應力的增大而減��；而卸荷過程試樣滲透率隨著有效應力的減小而增大，但卸荷過程滲透率并非是加荷過程的簡單逆過程，并建立了載荷煤體滲透率與有效應力的關系。對比了試樣滲透率演化的整體過程及規(guī)律，獲得了卸荷過程滲透率演化的三種典型路徑的概念模型，提出了與載荷煤體變形特征相對應的彈性滲透率模型、塑性滲透率模型和卸荷增透模型。 （4）根據(jù)鐵法礦區(qū)大隆煤礦煤層賦存特點，利用FLAC3D軟件對試驗礦區(qū)被保護層采動變形和應力變化進行模擬研究，得出被保護層采動變形和應力變化規(guī)律。結合滲透率演化實驗及模型，并利用Matlab中的Surf函數(shù)獲得了下被保護層滲透率空間分布規(guī)律，把卸壓采動影響區(qū)域的滲透率劃分為原始滲透區(qū)、彈性滲透區(qū)、塑性滲透區(qū)和卸荷增透Ⅰ區(qū)、卸荷增透Ⅱ區(qū)。根據(jù)研究結果，選取底抽巷穿層鉆孔對被保護層的卸壓瓦斯進行抽采，并抽采鉆孔的布置方式進行優(yōu)化。
[Abstract]:The coal seam pressure relief mining is through the stress release causes the coal body to produce a large number of new fissures, changes the coal body structure characteristic, impels the coal seam permeability to have the fundamental change, realizes the coal seam to resist the permeation to promote the gas drainage. This paper focuses on the coal seam pressure relief mining, the evolution characteristics of the permeability of the loaded coal body and the mechanism of fracture expansion of the coal body, and takes the theoretical analysis, experimental research, numerical simulation and engineering practice as the main means. The evolution of fracture and permeability of coal body during loading and unloading are studied, the evolution law of permeability and the corresponding model are obtained, and the results are applied to the study of permeability distribution characteristics of protected layer and gas extraction under pressure relief. The main conclusions of this paper are as follows: (1) the permeability experiments under different loading and unloading conditions are carried out using the mechanical path which is the same as the mechanical characteristics of the unloaded coal seams, and the standard raw coal samples are made. The permeability of Prida 7.5: 1 in different stratification directions is obtained. The reasons for the difference in permeability evolution during unloading are analyzed. It is concluded that the greater the initial damage degree of the specimen is under the same unloading point stress, the lower the ultimate unloading load strength is. As a result, the damage and deformation of specimen and the emergence of a large number of new fractures in the unloading process, the final permeability increases sharply and is larger than the permeability in the loading process. According to the results of permeation experiment, the experimental phenomenon and new understanding of antireflection of unloading are obtained. (2) by combining damage mechanics, unloading mechanics and seepage mechanics, the fracture initiation of different pre-bedded specimens under unloading is simulated by using RFPA2D / Flow software. The fracture evolution process and permeability change law of the specimen under loading conditions are obtained. The change of permeability is consistent with that of fracture evolution. Compared with the permeation experiment, it is pointed out that the more damage points and microcracks appear in the specimens at unloading points, the faster the microcracks spread after unloading, and the more the number of failure points are, and finally, the fracture deformation will occur easily. (3) according to the experiment of specimen permeability and the simulation of fracture evolution under loading condition, it is concluded that the permeability of specimen decreases with the increase of effective stress during loading. The permeability increases with the decrease of effective stress, but the permeability of unloading process is not a simple inverse process of loading process, and the relationship between the permeability of loaded coal and the effective stress is established. By comparing the whole process and law of sample permeability evolution, the conceptual models of three typical paths of permeability evolution in unloading process are obtained, and the elastic permeability model corresponding to the deformation characteristics of loaded coal is proposed. Plastic permeability model and unloading antireflection model. (4) according to the characteristics of coal seam occurrence in Dalong Coal Mine of Tiefa Mine, the mining deformation and stress change of protected layer in test mining area are simulated by FLAC3D software. The law of mining deformation and stress change of protected layer is obtained. Combined with the permeability evolution experiment and model, and using the Surf function in Matlab, the permeability distribution law of the lower protected layer is obtained, and the permeability of the area affected by unpressurized mining is divided into the original permeability area and the elastic permeable zone. Plastic permeation zone, unloading antireflection zone 鈪

本文編號：2267023