【作者】 张志敏；

【导师】 高文华；

【作者基本信息】 湖南科技大学 ， 矿业工程， 2018， 博士

【摘要】 软岩是软弱、松散、破碎、膨胀、流变、强风化蚀变和高地应力的岩体统称。软岩问题是从20世纪60年代被提出来的世界性难题,特别是煤矿软岩问题一直是困扰煤矿生产和建设的重要难题之一。红层泥岩是一种广泛分布且具有膨胀性的软岩,由于其沉积地质年代较新,结构连接普遍较弱,且含高岭石、伊利石和蒙脱石等粘土矿物,具有遇水易软化膨胀,失水收缩等特点。本文以红层泥岩为研究对象,对红层泥岩在荷载和水化共同作用下的膨胀和流变特征展开了大量的试验研究,并运用损伤力学和流变力学理论,构建了水化作用下红层泥岩的膨胀和流变损伤模型。本文主要进行了以下几个方面的研究:(1)红层泥岩膨胀特性试验研究;(2)红层泥岩膨胀机理及模型研究;(3)水化作用下红层泥岩基本力学特性试验研究;(4)红层泥岩流变特性试验研究;(5)红层泥岩的膨胀-蠕变损伤本构模型研究。通过以上研究得出了以下几点主要结论和创新点:采用自行设计的饱水装置,在RYL-600微机控制岩石剪切流变试验仪试验平台上实现了无侧限条件下的膨胀-蠕变试验,研究了干燥红层泥岩的无侧限膨胀特性、蠕变特性,得到红层泥岩在水化和荷载共同作用下的膨胀-蠕变耦合曲线。通过比较无侧限和侧限条件下的膨胀试验结果发现,对于红层泥岩在侧限条件的约束下极大的限制了其轴向的膨胀变形,同时在无侧限条件下,红层泥岩在水化过程中表现出膨胀-蠕变共同作用的特征。采用不同含水状态下的红层泥岩试件进行不同低加载速率单轴压缩试验,研究加载速率与含水率共同作用下红层泥岩的力学特征,分析了加载速率和水共同作用对红层抗压强度、弹性模量和峰值应变的影响。水对红层泥岩的强度劣化明显,红层泥岩峰值单轴抗压强度和弹性模量与含水率成负相关的关系,随着岩石含水率的增加红层泥岩的峰值单轴抗压强度和弹性模量呈线性关系降低。饱和红层泥岩样对加载速率最不敏感,在几种加载速率作用下峰值强度差异很小,干燥和天然状态的红层泥岩的峰值强度与加载速率都表现出正相关的关系,随着加载速率的增大峰值强度都存在明显的增大。水化和荷载耦合作用的单轴试验在不同加载速率作用下,其强度略高于饱和岩样的强度,且其峰值强度受加载速率影响明显,加载速率越小其峰值强度越小。同时,水化样破坏时的峰值应变明显小于其他三种含水状态的岩样,且破坏后岩样破碎程度也远高于其他三种状态。通过水化作用下的红层泥岩的膨胀和蠕变耦合试验,研究了在不同应力水平作用下岩样从干燥状态向饱和状态变化时,由于应力和水化膨胀耦合作用对岩样变形、长期强度以及破坏模式的影响。由于红层泥岩遇水软化和膨胀应力的作用,降低了红层泥岩出现加速蠕变的应力水平,同时也缩短了红层泥岩出现加速蠕变的时间。在水化和荷载共同作用下红层泥岩的蠕变变形曲线发展趋势和常规含水率不变的岩样的蠕变变形曲线明显不同,由于水化膨胀变形的影响,轴向变形逐渐减小,当减小到一定程度后,又开始逐渐增加,变形速率也缓慢增加,最后变形急剧增加而发生破坏。为了描述红层泥岩常规的蠕变变形特征,建立了变参数的西原蠕变模型描述了红层泥岩常规流变特征,同时,为描述水化膨胀以及岩石劣化特性,将损伤变量引入西原模型中,将变参数西原蠕变损伤本构模型与膨胀模型串联,建立符合水化作用下的红层泥岩的膨胀蠕变损伤模型。更多还原

【Abstract】 Soft rock is a general term for soft,loose,broken,expansive,rheological,strongly weathered alteration and high ground stress rock mass.The soft rock is a worldwide problem that was originally raised in the 1960 s,especially for the soft rock in coal mine,which has been one of the important problems with the production and construction.Red mudstone is widely distributed and swelling soft rock due to its relatively new sedimentary geological age and weak structure connection,and clay minerals such as kaolinite,illite and montmorillonite,which tend to soften and swell with exposure to water and shrink with loss of water.In this paper,the red mudstone was taken as the research object,and a large number of experimental studies were carried out on the expansion and rheological characteristics of the red mudstone under the combined action of load and hydration.By using damage mechanics and rheological theory,the model of swelling and rheological damage of the red mudstone under hydration was constructed.This paper mainly studies the following aspects :(1)experimental study on the expansion characteristics of red mudstone;(2)study on the expansion mechanism and model of red mudstone;(3)experimental study on the basic mechanical properties of red mudstone under hydration;(4)experimental study on rheological characteristics of red mudstone;(5)study on damage constitutive model of expansion and creep of red mudstone.Based on the above research,the main conclusions and innovations are drawn as follows:The swelling-creep test under the lateral unconfined condition was completed with a simple self-designed saturated equipment on the platform of microcomputer controlled rock shear rheological tester RYL-600.The swelling-creep coupling curve was presented under the effects of both hydration and load of red mudstone.By comparing the swelling test results under the confined lateral and unconfined lateral condition,it is found that for the red mudstone,the axial swelling deformation is greatly restricted under the constraint of the lateral confined condition.The red mudstone specimens under different water contents were applied for uniaxial compression test at differently low loading rates,the mechanical characteristics of red mudstone were studied under the impacts of both loading rate and water content,and the influence of the loading rate and water on the compressive strength,elastic modulus and peak strain of the red layer was analyzed.The strength of water toward the red mudstone is obviously weakened,and the peak compressive strength of the red mudstone and the elastic modulus are negatively correlated with the water content.The peak compressive strength and the elastic modulus of the red mudstone linearly decrease with the increase of the water content of the rock.The saturated red mudstone samples are the least sensitive to the loading rate,and the differences in peak strength are very insignificant under the effect of several loading rates.The peak strength of the dry and crude red mudstone shows a positivecorrelation with the loading rate,and the peak strength ascends obviously with the increase of loading rate.Under different loading rates,the strength of the uniaxial test of hydration and load coupling is slightly higher than that of the saturated rock sample,and its peak strength is significantly affected by the loading rate.The peak strength gets smaller as the loading rate is smaller.Meanwhile,the peak strength of hydrated sample is obviously less than that of other three different rock samples of water content,and the failure degree of rock samples is much higher than that of other three samples.The effects of stress and hydration swelling on deformation,long-term strength and failure mode of rock samples were studied under different loads from dry state to saturated state through the coupling test of swelling and creep of red mudstone under hydration.The stress level of accelerated creep of red mudstone is reduced,and the time of accelerated creep of red mudstone is shortened due to the effect of water softening and swelling stress.The creep deformation trend and the creep deformation of general water content for the sample rocks are obvious different under the joint interaction of hydration and load.The axial deformation decreases gradually because of the influence of hydration swelling deformation,and it begins to increase gradually when reduced to a certain degree.Correspondingly,the deformation rate steadily increases,and finally it builds dramatically and produces damage.The west of the original changed parameters creep model was established to describe the conventional rheological characteristics of red mudstone.The damage variables were employed into the west of the original model,the creep damage constitutive model of west changed parameters and swelling model were jointed,set up under the hydration of the swelling creep damage model of red mudstone was established under hydration in order to better present the hydration swelling and degradation characteristics of rock damage.更多还原