煤矿深部采区冲击危险评价及防治研究

基于某矿-1 000m东一下山采区的条件,对其进行冲击危险性分析,在此基础上建立冲击矿压综合控制体系,即,开采前进行区域性防冲优化设计,确定工作面停采线位置、上下煤层之间巷道或工作面布置、区段煤柱宽度及接替顺序等参数;开采期间采取煤体大直径钻孔、煤体爆破及顶板预裂爆破等局部性卸压方案;强冲击煤层巷道采用"三结构"组合加固支护。     

双孔致裂条件下的层状岩石多场耦合分析

页岩气储层渗透率比常规储层低,通过水平井体积压裂产生复杂裂网可以改善储层结构,而双孔致裂条件下两孔之间的互相干扰对裂网的扩展具有重要影响。利用数值仿真试验对双孔水压致裂条件下的裂网演化过程进行研究,并与理论分析作对比,结果表明:层理方向、原生裂纹等对裂网扩展规律有显著影响,当层理与原生裂纹夹角较小时,随着应力在原生裂纹尖端的累积,主裂缝沿原生裂纹向远端扩展,当层理与原生裂纹夹角较大时,主裂缝贯穿原生裂纹向前发展;两注水孔中间产生一条主裂缝,最后岩石沿此主裂缝发生失稳破坏,失稳破坏的最大剪应力与计算值大致吻合。研究成果可为水平井压裂设计提供参考。     

基于应力波理论的台阶爆破孔网参数计算

为了提出合理的台阶爆破孔网参数,基于爆炸应力波传播理论和波的透射原理,计算得到爆炸粉碎区半径为0.9m,裂隙区半径为4.2m。每个炮孔爆炸致裂范围由粉碎区和裂隙区半径相加而得,该工况条件下致裂范围半径约5.1m。通过ANSYS/LS-DYNA程序对台阶爆破耦合装药条件下爆破裂隙扩展过程进行模拟,得出合理的炮孔间距为2倍致裂范围半径,第一排炮孔距自由面的平均距离为1倍致裂范围半径。     

基于液压致裂法的PBX炸药内部拉伸应力测试可行性研究

为了满足高聚物黏结炸药(PBX)内部拉伸应力测试的需要,利用液压致裂法和孔边应力状态修正实验,建立了基于液压致裂法的PBX炸药内部拉伸应力测试方法。为验证测试方法的有效性,采用材料万能试验机模拟构件内部拉伸应力,结合自主搭建的PBX液压致裂测试平台,开展了不同拉伸应力下的液压致裂应力测试实验。结果表明,直接利用液压致裂法能定性描述PBX炸药的内部拉伸应力,测试结果与预加拉伸应力有较好的相关性(相关系数为98.90%),但不能定量描述;通过对带孔试样进行单轴拉伸实验,获得孔边有效应力集中系数,对液压致裂法的孔边应力状态进行修正,修正后的应力值与预加应力吻合较好,平均相对误差10.67%。建立的测试方法不受测试深度限制,理论上可以测出拉伸应力的大小和方向,是一种基于液压致裂法的PBX炸药内部拉伸应力定量测试方法。     

提高煤层瓦斯抽放率的高能气体致裂技术研究

把高能气体压裂技术应用于煤矿的瓦斯抽放 ,提高煤矿井下的瓦斯抽放率 ,为安全生产提供保障。本文对高能气体压裂技术应用于煤层致裂进行了研究。设计了满足井下特殊环境的致裂弹和相应的井下施工工艺     

深孔爆破放顶在瓦斯治理中的应用

基于深孔爆破技术在岩体致裂方面的实践应用,以丁集煤矿1432(1)工作面为工程背景,试验了采用深孔预裂爆破技术强制放顶在工作面瓦斯治理中的作用。对比深孔预裂爆破放顶前后的工作面瓦斯涌出量,结果表明:施工深孔爆破后,工作面风排瓦斯浓度提高44%,风排瓦斯量提高58%,表明超前深孔爆破强制放顶技术对工作面瓦斯治理具有较好效果。     

分层煤层开采压裂优化计算模型

在选择煤层压裂参数和开采布置存在不确定性的问题,通过最大拉应力理论的断裂失效准则,得到多分层煤层压裂的计算模型。在煤层为均质、连续、各项同性的地质体下,每层的起裂压力与煤层埋深为线性递增关系,和理论计算的变换规律一致。通过对煤层结构和应力场特点分析,明确注水压力计算方法,在轴向上主要受到最弱层理面,在径向上主要影响最小抗拉强度和垂直侧向应力系数。     

煤层群开采冲击地压监测与防治技术研究

以4401工作面为研究对象,采用RFPA模拟软件分析了近距离煤层不同煤间距巷道变形破坏情况,并得到超前支承压力峰值以及明显影响范围。根据工作面地质条件,将工作面划分为四个危险区域,掘进期间在不同危险区域采用煤层注水、爆破卸压进行冲击地压防治;在回采期间采用大直径钻孔、匀速慢推进行冲击地压防治。采用钻屑法对卸压效果进行检验,结果表明卸压后基本无冲击地压危险。     

预裂爆破在我矿的应用

南京白云石矿应用预裂爆破技术处理边坡工程是切实可行的,利用它的不偶合作用,减轻对边帮保留岩体的破坏程度。根据岩石性质,合理地确定预裂爆破工艺参数至关重要,另外为保证预裂爆破效果,还应注意钻孔的施工质量,即预裂孔的孔位、角度,方向和深度均应符合设计要求。     

岩石爆破裂纹扩展机理试验研究

光面爆破是应用最为广泛的一项控制爆破技术,可以大大减少巷道掘进中的超欠挖现象。为探究爆破荷载下裂纹成缝及扩展机理,采用有机玻璃板制作2组试件进行单孔起爆试验,结果表明：爆破的第一阶段主要是爆轰应力波的作用,其致裂炮孔周边及破碎孔口岩体,在炮孔周边形成了细小裂纹;在爆破的第二阶段,爆生气体的气楔作用促使裂纹进一步扩展,爆生气体的逸散行为导致了玻璃碎片抛掷现象;在爆破的第三阶段,爆生气体的作用已很微弱,裂纹扩展逐渐停止,而在反射拉伸波到达裂纹尖端时,对裂纹表面的拉伸作用促使裂纹沿反射拉伸波传播方向进一步扩展。     

南京地区粉土的不排水三轴压缩试验

通过全自动三轴仪进行了南京地区粉土的三轴不排水的试验,研究了围压和干密度对应力-应变曲线、孔隙水压力曲线和有效主应力比曲线的影响.试验表明:高围压状态下粉土试样呈现出弱应变软化型,而低围压状态下呈现出应变稳定型;低围压下试样在加载初期产生正孔隙水压力,随后产生负孔隙水压力,其后基本保持稳定;干密度越大,主应力差峰值越大,表现出较大的剪胀性,孔隙水压力易出现负孔隙水压力;干密度值较高时,土样处于密实状态,表现出剪胀特性,有效主应力比-应变曲线近于应变软化型;围压较低、干密度较大时,试样易表现出软化特征,试样出现剪切带破坏,强度明显下降.     

Experimental study of the hydro-mechanical behaviour of the Callovo-Oxfordian argillite

Various laboratory experiments were carried out in the framework of the MODEX-REP project on the Callovo-Oxfordian argillite core samples taken from the Meuse/Haute-Marne Underground Research Laboratory (MHM-URL) in Eastern France to provide basic data for modelling the hydro-mechanical response of the argillite to shaft sinking. The short-term mechanical behaviour of the argillite was investigated by means of uniaxial and triaxial compression tests, whereas the long-term behaviour was studied by uniaxial creep and relaxation tests. Some influence factors such as material anisotropy, scale effect, water content and sample origin were examined. Permeability of the argillite was determined on wet and dry specimens parallel and perpendicular to the bedding plane by using gas under different confining pressures. With regard to the short-term mechanical behaviour, scale and anisotropy effects were observed. The compressive strength and the failure strain of the air-dried specimens are about two times higher than those of the saturated ones. No lower creep limit, no significant scale effect and no significant anisotropy effect on the pure creep behaviour for the argillite were found. The long-term mechanical behaviour of the investigated region of the argillaceous formation is relatively homogeneous. The gas permeability parallel to the bedding plane is about one order of magnitude higher than that perpendicular to the bedding and decreases with increasing confining pressure and water content.     

低温下泡沫混凝土的动态力学性能

为了研究低温下泡沫混凝土的动态力学性能,采用φ100 mm的铝制分离式霍普金森压杆(SHPB)装置对不同温度下泡沫混凝土试件进行冲击压缩试验,得到了不同温度、应变率下的泡沫混凝土的应力应变曲线、能量参数、破碎形态等。结果表明:当应变率在62.59 s^-1以下时,泡沫混凝土应力应变曲线分为线弹性阶段、屈服阶段、破坏阶段;当应变率超过62.59 s^-1时,其应力应变曲线分为线弹性阶段、屈服阶段、局部失稳、应力平台、破坏阶段;常温、0 ℃、-10 ℃、-20 ℃和-30 ℃下,泡沫混凝土的动态抗压强度以及吸收能在对应的应变率分界点前表现出显著的应变率效应,但超出该分界点后,应变率效应便不再明显;泡沫混凝土的动态峰值抗压强度与吸收能随温度的降低而提高,但峰值应变随温度降低而降低;泡沫混凝土冲击破碎后的块度随着温度的降低逐渐变大。在低温环境下泡沫混凝土的抗动载设计中,对于泡沫混凝土的峰值抗压强度、吸收能,应优先考虑温度效应的影响,而对于其峰值应变,应优先考虑应变率效应。     

Impact of characteristic length and loading rate upon dynamic constitutive behavior and fracture process in alumina ceramics

Understanding the impact performance of ceramic materials requires accurate corresponding relationship between mechanical response and fracture behavior. In this study, constitutive behaviors of alumina ceramics were successfully determined via split-Hopkinson pressure bar (SHPB) system coupled with high-speed camera to track the deformation and failure process. Failure strength of alumina demonstrated a strong dependency on strain rate beyond a critical value (namely transition strain rate). Inelastic deformation in the dynamic stress-strain curves implied that degradation of modulus does occur. The incorporating such degradation (damage evolution) in modulus enabled a more accurate evaluation of transition strain rate as a function of characteristic length of specimen. On-line observation revealed that longitudinal cracks dominated the failure process of alumina with negligible interfacial friction. However, interfacial friction became significant with the decreased characteristic length, thus the inclined cracks dominated fracture in alumina. It was found that the effect of interfacial friction can be minimized by lowering the impact velocity to maintain the uniaxial loading status in SHPB loads. Finally, it is suggested that an aspect ratio of 1.0 for the specimen should be suitable for alumina due to its insensitivity to interfacial friction within the achievable strain rate.     

Behaviour of Slurry Infiltrated Fibre Concrete (SIFCON) under triaxial compression

Slurry infiltrated fibre concrete (SIFCON) is one of the recently developed construction material that can be considered as a special type of high performance fibre reinforced concrete (HPFRC) with higher fibre content. In the current research, triaxial compressive behaviours of high strength concrete (HSC), HPFRC and SIFCON were investigated. Purposefully, laboratory tests employed on four types of 75 × 150 mm cylindrical specimens with different steel fibres volumes (0, 2, 5 and 10%). All tests were conducted under four different confining pressure levels (0, 5, 15 and 21.5 MPa) according to triaxial conditions. Consequently, stress-strain curves were obtained and governing failure patterns and failure criterions of HSC, HPFRC and SIFCON samples were discussed. According to the results increasing of fibre volumes increases peak stress, energy absorption, toughness and Poisson's ratio while increasing confining pressures increases peak stress, energy absorption and toughness. Also, this may cause concrete to behave as a plastic material.     

Stress versus strain relationship of high strength concrete under high lateral confinement

A common application of high strength concrete (HSC) is in columns subjected to large compressive forces. However, a major problem is the insufficient ductility available in HSC columns. To determine the required lateral reinforcement to maintain sufficient ductility, a good understanding of the stress-strain behaviour of confined concrete needs to be established. This paper describes a testing program carried out to obtain experimental data of complete (ascending and descending) stress-strain relationships between axial stress, axial strain and lateral strain for HSC. Compressive strengths of concrete tested were 100 MPa and 60 MPa. The confining pressures used were 4 MPa, 8 MPa and 12 MPa. A total of 18 stress-strain curves are presented. The experimental results obtained seem to indicate that, for high confining pressures, the lateral strain at peak stress for 100 MPa concrete was 20% less than that of the 60 MPa concrete.     

粘性土应力路径试验

利用GDS多功能三轴仪,对南京河西地区原状粘性土进行了常规三轴压缩、减压三轴压缩和等p应力路径的固结不排水三轴试验,探讨不同应力路径下粘性土的变形和强度特性。实验表明:不同应力路径下土的应力应变关系都呈曲线形态相似的非线性应变硬化型,而土的峰值强度和土中孔隙水压力差异明显;相同应力路径试验得到的有效应力路径形态一致,常规三轴压缩试验中有效应力路径呈S形。     

早期受冻损伤混凝土应力-应变试验研究

北方地区混凝土冬季施工过程,新浇筑混凝土容易因突然降温而遭受早期损伤.为研究早期受冻对混凝土单轴受压状态下力学性能的影响,通过对不同冻结温度(-5℃、-10℃)、不同起冻时刻(1.0 h、3.5 h、8.0 h、24.0 h)养护条件下的混凝土进行单轴受压试验,获得了应力-应变全曲线,拟合得到了适用于早期受冻混凝土的单...     

基于数字图像相关法的熔融沉积聚乳酸材料动态力学性能测试

为研究熔融沉积聚乳酸（PLA）材料动态的力学性能,利用分离式霍普金森压杆（SHPB）装置对PLA材料进行了加载应变率分别为880、1 230、1 650、2 230 s^-1的动态压缩实验,通过高帧率图像采集设备获得了不同应变率下PLA材料的变形图像,结合数字图像相关（DIC）法分析得到PLA试样表面沿加载方向的应变场,并对应变率进行了分析。结果表明,熔融沉积PLA材料在动态载荷作用下的变形过程存在弹性阶段、塑性阶段和卸载阶段;随着应变率的增加,PLA材料在塑性阶段出现了显著的塑性流动区域;PLA材料的压缩强度和最大应变均随应变率增大而增大;利用DIC法测得在整个动态冲击实验过程中,应变在试样中分布基本均匀,应变范围随应变率增大而增大,应变率在整个加载过程中基本保持恒定;DIC法测得的应变与SHPB实验基本一致,应变率误差均小于3 %,表明本研究使用的DIC法能够应用于SHPB实验。     

PP/PA/TPEg共混高聚物材料动态力学性能的研究

本文用霍布金生压杆装置（简称SHPB）试验技术研究了两种不同配比的PP/PA／TPEg共混高聚物材料在高应变率（10^2-10^3s^-1）下的动态力学行为。实验表明，准静态下的应力一应变曲线与高应变率下的有较大差别，其动态的杨氏模量、屈服应变随应变率的增大而增大，PP／PA共混材料是一种应变率敏感的高聚物材料。