二氧化碳影响水泥-岩石界面胶结率的实验研究

研究了不同条件下二氧化碳对水泥-岩石胶结率的影响。为了研究胶结率或脱粘率,在实验中,制备了12种不同胶结方式的岩样。为了解二氧化碳和模拟地层水对水泥-岩石及其界面的影响,让岩样在注入潮湿二氧化碳的环境下反应10 d。最后用μ-CT扫描岩样,观察界面的胶结情况和孔隙情况,并采用胶结面积定量描述界面胶结率。实验结果表明,页岩的胶结率比砂岩要高;而含有泥饼或泥浆流体覆盖的岩样具有较低的胶结率,但有泥饼的岩样比有泥浆的岩样胶结率要好。同时对比实验前后岩样的胶结率发现,胶结率变化程度不大,但经过二氧化碳实验的岩样出现了降解现象。

一种实用的定量表征岩石视压实率和视胶结率的实验方法

对于目前分布最为广泛的砂岩储层,压实和胶结等成岩作用会影响砂岩储层的物性、弹性等物理性质并最终决定岩石颗粒的接触性质和孔隙结构特征.根据前人的研究,定量表征岩石压实和胶结作用的参数主要有视压实率和视胶结率、成岩综合系数等.目前尚缺乏一套系统完整的实验方法来确定岩石的成岩系数.实际应用时,前人多根据经验公式和薄片资料来确定原始孔隙度和胶结物含量,误差较大,流程复杂.本文立足实验手段,在前人研究的基础上,提出了一套系统的实验室确定视压实率和视胶结率的方法.结果表明,实验获得的视压实率、视胶结率与孔隙度、渗透率以及分选系数等存在较好的相关关系,符合前人研究的结果.

基于声波衰减率的声幅刻度及质量控制方法

根据声波测井原理,在固井质量评价中,声波首波衰减率与相对幅度具有同等意义,在已知套管内径和厚度的前提下,声波衰减率可以通过计算转换为相对幅度,在无自由套管情况下实现相对幅度刻度,本文论述了采用声波衰减率原理进行相对幅度刻度的可行性,分析了实际生产中影响刻度质量的关键因素并提出了控制方法。

压实作用和胶结作用对鄂尔多斯长_8储层的影响

为探讨压实作用和胶结作用对鄂尔多斯盆地长_8储层孔隙度的影响,将长_8储层按区域分为5个体系,运用矿物岩石学和统计学方法对压实、胶结作用进行系统研究。对压实率、胶结率、孔隙度变化与压实-胶结作用的相关性进行定量计算。研究发现,压实作用具有早期快速埋深和埋藏时间长的特点;胶结作用发生于整个成岩过程,包括硅质和碳酸盐胶结。压实率统计表明,储层处于中等—强压实程度。压实作用造成的长_8~1层各体系孔隙度损失:东北>西北>南部>西南>西部;长_8~2层:西北>西部>西南>东北>南部。压实孔隙度损失平均大于19%。胶结率统计表明,储层为弱—中等胶结,胶结孔隙度损失在11%～16%。胶结作用造成的长1/8层各体系孔隙度损失:西部>东北>西北>南部>西南,长2/8层:东北>南部>西部>西南>西北。压实作用对孔隙度造成的损失比胶结作用大,是鄂尔多斯长_8储层物性的主要破坏作用。

甲烷水合物三维离散元模拟参数反演初探

含填充型水合物的砂性能源土可视为特殊的散粒体材料(砂粒和水合物颗粒混合物),具有明显的非连续特征。在离散元中若采用团粒(胶结成团的颗粒组)模拟填充水合物颗粒则需合理确定团粒结构内颗粒间胶结模型参数。为此,基于前人的室内纯水合物三轴试验资料进行离散元建模与参数反演。结果表明,宜采用松散且颗粒间摩擦系数较小的试样模拟水合物块体,当颗粒间摩擦系数小于等于0.04时,可确保无胶结试样的内摩擦角小于室内试验获得的纯水合物内摩擦角。胶结刚度只需在较小范围变化即可反映相同温度不同围压条件下的弹性特性,且微观刚度参数与胶结强度参数的相互作用较小,可以假定二者相互独立。通过选取不同的微观胶结强度值进行不同围压下的三轴压缩试验,建立微观胶结强度参数与宏观参数(内摩擦角和黏聚力)之间的关系,从而确定与室内试验强度特性相符合的微观胶结强度值,实现甲烷水合物三轴试验离散元模拟;由体变规律可知,甲烷水合物在发生剪胀前均存在一个初始的体积收缩阶段,且剪胀特性随着围压的减小而呈现增强趋势。通过微观变量颗粒接触方向组构的分布图可知,随着轴向应变增大,颗粒间接触主方向朝竖直方向偏转,表现出明显的各向异性特性。随着轴向应变的增大,颗粒间胶结残余率变小,表明试样逐步破坏。

Resistivity and thermal infrared precursors associated with cemented backfill mass

The stability of cemented backfill mass is important to keep miners and equipment safe in underground backfill miming.The stress-strain behavior, resistivity and thermal infrared(TIR) characteristics of backfill mass under uniaxial compression were investigated. The monitoring system consisted of a TIR observation system, a stress-strain monitoring system and a resistivity measurement system. Precursory information for impending failure of cemented backfill mass was collected, including TIR, strain and resistivity precursors. The sensitivity and difference of different monitoring information to the same failure event were compared.The results show that the time-space evolution process of the resistivity and TIR is basically the same as the whole process from compression deformation to failure of backfill mass, and the time variation of resistivity and TIR is obviously characterized by stage.The resistivity precursor turns out earlier than the TIR and the strain. The resistivity relation with loading compression is anti-symmetry, decreasing as the compression stress increases before the peak strength of backfill mass. However, when the backfill mass enters into the phase of failure, the resistivity starts to increase as the stress increases. The change of the resistivity growth direction can be regarded as the resistivity-caution-point for the failure of backfill mass under uniaxial compression. It is also indicated that the TIR information mainly represents the surface temperature evolution in the process of compression before the backfill enters into the plastic-yield state. It can be a valuable tool to obtain the precursors for failure of cemented backfill mass for backfill mines.

Mechanical properties of bimrocks with high rock block proportion

For the investigation of mechanical properties of the bimrocks with high rock block proportion,a series of laboratory experiments,including resonance frequency and uniaxial compressive tests,are conducted on the 64 fabricated bimrocks specimens.The results demonstrate that dynamic elastic modulus is strongly correlated with the uniaxial compressive strength,elastic modulus and block proportions of the bimrocks.In addition,the density of the bimrocks has a good correlation with the mechanical properties of cases with varying block proportions.Thus,three crucial indices(including matrix strength)are used as basic input parameters for the prediction of the mechanical properties of the bimrocks.Other than adopting the traditional simple regression and multi-regression analyses,a new prediction model based on the optimized general regression neural network(GRNN)algorithm is proposed.Note that,the performance of the multi-regression prediction model is better than that of the simple regression model,owing to the consideration of various influencing factors.However,the comparison between model predictions indicates that the optimized GRNN model performs better than the multi-regression model does.Model validation and verification based on fabricated data and experimental data from the literature are performed to verify the predictability and applicability of the proposed optimized GRNN model.

全风化花岗岩注浆加固体抗冲刷特性试验研究

突水突泥是全风化花岗岩隧道施工中常见的地质灾害,土体颗粒的流失和抗冲刷特性是决定全风化土体发生突水的关键因素。为了研究注浆加固体颗粒流失与抗冲刷特性,自行设计注浆试样制备及抗冲刷试验装置,能够实现全风化花岗岩劈裂、挤密注浆试样制作,以及模拟注浆加固体受水流冲刷的关键过程。利用该试验装置开展注浆量、动水流速、养护龄期、土体初始含水量等因素对注浆加固体的颗粒流失与抗冲刷特性试验研究,并定义颗粒流失率指标来定量评价土体颗粒流失与抗冲刷特性。试验表明:注浆加固体抗冲刷特性随注浆量及其养护龄期的提高均明显改善,动水流速的增加显著加大颗粒流失,含水量过低或过高时,加固体的抗冲刷特性均较差,存在一个最佳含水量值使得抗冲刷特性最优。同时,单位浆液量胶结土体范围(浆液胶结率)随注浆量呈二次抛物线变化,且浆液胶结率峰值随动水流速的提高向高注浆量方向移动。最后,根据试验结果提出地层注浆量的计算方法及含水量分区治理的原则。

Effect of treatment process on consolidation efficiency of fugitive dust cemented by bio-activated cementitious material based on CO2 capture

As a new green and environmental material, bio-activated cementitious material is attracting extensive attention. This study confirmed that the bio-activated cementitious material could mineralize and cement fugitive dust into the cal- cite-consolidation-layer based on CO2 capture and utilization. The results illustrated that treatment processes （non-pressure spraying, pressure spraying, non-pressure blending and pressure blending） had a strong effect on the microstructure and prop- erties of calcite-consolidation-layer. According to the analysis of X-ray diffraction （XRD） and Fourier transform infrared （FTIR）, calcite was prepared by bio-activated cementitious material during the cementation process. Meanwhile, scanning electron microscopy （SEM） and thermogravimetric-differenfial scanning calorimetry （TG-DSC） were adopted to measure the corresponding variation of porous characteristics and calcite content caused by different treatment processes. The results indi- cated that the microstructure of calcite-consolidation-layer from the spraying process had lower porosity and higher content of calcite than from blending processes. In addition, the mechanical properties of calcite-consolidation-layer were also tested. The hardness and compressive strength, which reached 19.5 GPa and 0.6 MPa, respectively, of calcite-consolidation-layer from the pressure spraying process were higher than those from the other three treatment processes. Compared with the non-treatment process, the four treatment processes had superior wind erosion resistance. Under the wind speed of 12 m/s, the mass loss of calcite-consolidation-layer from the pressure spraying process decreased from 2150.2 to 23.8 g/（m^2 h）.