【摘要】：我國新疆、山西等地現(xiàn)存大面積煤田火區(qū),煤火不僅燒毀大量煤炭資源,而且嚴重破壞西部脆弱生態(tài)環(huán)境。煤火演化過程中,火區(qū)上部覆巖產(chǎn)生燃燒裂隙,形成新的火區(qū)供風(fēng)通道被認為是火區(qū)得以進一步持續(xù)發(fā)展主要因素之一。燃燒裂隙的產(chǎn)生是火區(qū)煤炭燒損火區(qū)原有煤巖受力結(jié)構(gòu)發(fā)生改變和熱力耦合作用下覆巖熱力學(xué)參數(shù)變化共同作用的結(jié)果。認識火區(qū)覆巖變溫條件下峰值應(yīng)力、彈性模量等熱力學(xué)參數(shù)的變化規(guī)律,分析其隨溫度變化的受熱失穩(wěn)特性,對于揭示煤田火區(qū)的演化機制具有十分重要的意義。煤田火區(qū)覆巖多以砂巖、粉砂巖、泥巖為主,目前針對砂巖和泥巖的研究較多,而粉砂巖的研究極少。因此,論文以火區(qū)粉砂巖為研究對象,開展升/降溫條件下的熱力學(xué)參數(shù)實驗并對熱力學(xué)參數(shù)與受熱失穩(wěn)特性進行分析研究,推動對火區(qū)燃燒裂隙產(chǎn)生規(guī)律的認識,并且對火區(qū)的治理與數(shù)值模擬提供一定指導(dǎo)。本文圍繞煤田火區(qū)粉砂巖開展原位、單軸、X衍射等實驗,主要研究內(nèi)容和成果如下:采用高溫高壓巖體三軸試驗機對粉砂巖低圍壓(2MPa),常溫~600℃范圍內(nèi)的透氣性變化開展了原位實驗,發(fā)現(xiàn)在常溫~600℃范圍內(nèi),粉砂巖滲透率隨溫度的升高呈“V”字形演化趨勢,在升溫過程中粉砂巖的滲透率在300℃左右表現(xiàn)出清晰的溫度門檻值特性,300℃之前滲透率呈減小趨勢,300℃之后滲透率開始增大;結(jié)合聲發(fā)射特征實驗與熱物性實驗分析可知,滲透率變化是由熱膨脹系數(shù)、導(dǎo)熱系數(shù)等參數(shù)變化引起熱破裂階段變化所致。采用MTS810實驗系統(tǒng)開展了粉砂巖的高溫單軸力學(xué)實驗,測試最高溫度為800℃,實驗發(fā)現(xiàn)出實時升溫條件下粉砂巖的峰值應(yīng)力隨溫度的升高整體上呈先減小后增大再減小的趨勢、彈性模量隨溫度升高整體呈先增大后減小的趨勢;隨著溫度的升高,100℃的降溫損傷對粉砂巖抗變形能力的影響呈波動式下降、對峰值應(yīng)力的影響在高溫段(400℃~600℃)影響較大;粉砂巖力學(xué)參數(shù)的變化是由物相變化、熱破裂、礦物組分等原因造成,并且結(jié)合X衍射分析可知,脆性破壞除與彈性模量相關(guān),還可能受方解石、石英等礦物組分含量的影響。結(jié)合力學(xué)參數(shù)、脆性系數(shù)、破壞形態(tài)探究出升溫條件下,粉砂巖在常溫~200℃溫度段抗壓能力呈線性下降,導(dǎo)致覆巖抗壓能力低于平衡應(yīng)力,裂隙進一步發(fā)育擴大;200℃~700℃溫度段,粉砂巖逐漸轉(zhuǎn)為脆性破壞,雖然隨著溫度的增加粉砂巖抗壓能力增加,但是溫度的升高火區(qū)煤的燒損量越來越大,覆巖受力平衡結(jié)構(gòu)發(fā)生改變,一旦超過峰值應(yīng)力就會發(fā)生脆性破壞,產(chǎn)生大量燃燒裂隙,并在700℃達到最大;當超過700℃,抗變形能力與抗壓能力急劇下降,粉砂巖逐漸失去抗壓能力并開始軟化,致使巖石再次呈延性破壞。
[Abstract]:A large area of coal field fire exists in Xinjiang, Shanxi and other places in China. Coal fire not only burns down a large number of coal resources, but also seriously destroys the fragile ecological environment in the west. In the process of coal fire evolution, the overburden rock in the upper part of the fire area produces combustion cracks, and the formation of a new air supply channel in the fire area is considered to be one of the main factors for the further sustainable development of the fire area. The formation of combustion cracks is the result of the change of the original coal and rock stress structure and the change of thermal mechanical parameters of overlying rock under the action of thermodynamic coupling. It is of great significance to understand the variation of thermodynamic parameters such as peak stress and elastic modulus under the condition of variable temperature of overlying rock in fire area, and to analyze the thermal instability characteristics of overlying rock with temperature, which is of great significance to reveal the evolution mechanism of coal field fire area. Most of the overburden rocks in coalfield fire area are sandstone, siltstone and mudstone. At present, there are many studies on sandstone and mudstone, but the research on siltstone is very few. Therefore, taking siltstone in fire area as the research object, the experiment of thermodynamic parameters under the condition of rising / cooling is carried out, and the thermodynamic parameters and thermal instability characteristics are analyzed and studied in order to promote the understanding of the law of combustion cracks in fire area. It also provides some guidance for the treatment and numerical simulation of fire area. In this paper, in situ, uniaxial and X-ray diffraction experiments are carried out on siltstone in fire area of coalfield. The main research contents and results are as follows: low confining pressure (2MPa) of siltstone is studied by triaxial testing machine of high temperature and high pressure rock mass. In situ experiments were carried out on the variation of air permeability in the range of room temperature ~ 600 鈩，

本文編號：2491018