Research of dynamic mechanical performance of cement rock

As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock.Dynamic fracture toughness of cement rock will be changed under the influence of filler. In order to study the damage mechanism of the cement circle during perforation and carry out comprehensive experiments on preventing and resisting connection, a kind of comprehensive experiment equipment used to simulate perforation and multi-functional equipment for testing the dynamic properties of the material are designed. Experimental study of the dynamical mechanical performance of original and some improved cement rock and experiment used to simulate the well cementation and perforation are carried out. Standard for dynamical mechanical performance of the cement rock with fine impact resistance and mechanical properties of some improved cement rock are also given.

Measuring dynamic fracture toughness of cement rock using a short rod specimen

As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock. Dynamic fracture toughness of cement rock will be changed under the influence of filler. In this paper, short rod specimens of cement rock are employed in the experiments to investigate the dynamic fracture toughness of cement rocks with different ingredients using split Hopkinson Pressure Bar, and partial experimental results are given. The results indicate that fiber reinforcement is an effective way to improve the impact resistance of cement rock.

Theoretical analysis of a new segmented anchoring style in weakly cemented soft surrounding rock

According to the tensile failure of rock bolt in weakly cemented soft rock, this paper presents a new segmented anchoring style in order to weaken the cumulative effect of anchoring force associated with the large deformation. Firstly, a segmented mechanical model was established in which free and anchoring section of rock bolt were respectively arranged in different deformation zones. Then, stress and displacement in elastic non-anchoring zone, elastic anchoring zone, elastic sticking zone, softening sticking zone and broken zone were derived respectively based on neural theory and tri-linear strain softening constitutive model of soft rock. Results show that the anchoring effect can be characterized by a supporting parameter b. With its increase, the peak value of tangential stress gradually moves to the roadway wall, and the radial stress significantly increases, which means the decrease of equivalent plastic zone and improvement of confining effect provided by anchorage body. When b increases to 0.72, the equivalent plastic zone disappears, and stresses tend to be the elastic solutions. In addition, the anchoring effect on the displacement of surrounding rock can be quantified by a normalization factor δ.

Water-resisting ability of cemented broken rocks

Using the self-designed testing system, the seepage tests for cemented broken rocks were conducted, and the impact of different factors on water-resisting ability was analyzed. The results show that(1) seepage process of the cemented broken rocks can be divided into two categories: in one category, seepage instability occurs after a period of time, in the other, the permeability decreases slowly and tends to be stable,and seepage instability does not occur;(2) cementing performance of cementing agent and grain size distribution are the decisive factors for water-resisting ability, with the increase of cementing performance and the mass percentage of large grains, the water-resisting ability of the specimen strengthens;(3)aggregate type has little effect on seepage stability, for the specimens with different aggregate types,the permeability and the duration of seepage instability have small difference;(4) initial porosity has a certain effect on the water-resisting ability of the specimen, but has no decisive role. With the increase of the initial porosity, the duration of seepage instability decreases.

Characterisation, Analysis and Design of Hydrated Cement Treated Crushed Rock Base as a Road Base Material in Western Australia

Hydrated Cement Treated Crushed Rock Base （HCTCRB） is widely used as a base course in Western Australian pavements. HCTCRB has been designed and used as a basis for empirical approaches and in empirical practices. These methods are not all-encompassing enough to adequately explain the behaviour of HCTCRB in the field. Recent developments in mechanistic approaches have proven more reliable in the design and analysis of pavement, making it possible to more effectively document the characteristics of HCTCRB. The aim of this study was to carry out laboratory testing to assess the mechanical characteristics of HCTCRB. Conventional triaxial tests and repeated load triaxial tests （RLT tests） were performed. Factors affecting the performance of HCTCRB, namely hydration periods and the amount of added water were also investigated. It was found that the shear strength parameters of HCTCRB were 177 kPa for cohesion （c） and 42~ for the internal friction angle （~）. The hydration period, and the water added in this investigation affected the performance of HCTCRB. However, the related trends associated with such factors could not be assessed. All HCTCRB samples showed stress-dependency behaviour. Based on the stress stages of this experiment, the resilient modulus values of HCTCRB ranged from 300 MPa to 1100 MPa. CIRCLY, a computer program based on the multi-layer elastic theory was used in the mechanistic approach to pavement design and analysis, to determine the performance of a typical pavement model using HCTCRB as a base course layer. The mechanistic pavement design parameters for HCTCRB as a base course material were then introduced. The analysis suggests that the suitable depth for HCTCRB as a base layer for WA roads is at least 185 mm for the design equivalent standard axle （ESA） of 10 million.

Finite element analysis of thermal residual stresses at cemented carbide rock drill buttons with cobalt-gradient structure

The aim of this study is to apply the concept of functionally graded materials(FGMs) to cemented carbides and to develop high-performance rock drill buttons. Cobalt-gradient structure was introduced to the surface zone of the buttons by carburizing process. Finite element method and XRD measurement were used to decide the distribution of thermal residual stress. Constitutive parameters were determined by constraint factor. Numerical results show that residual stresses of gradient buttons mainly concentrate in cobalt-gradient zone. There is compressive stress in the surface zone and tensile stress in the cobalt-rich zone. The maximum value of surface compressive stress is 180 MPa for WC-6Co cemented carbides. And the numerical results agree with the results of XRD measurement.

基于RSM的超细水泥注浆材料配比及性能优化模型

注浆堵水技术已成为水害措施防范向工程治理不可缺少的技术之一,超细材料的研究也成为了目前注浆材料发展的新方向。为了解决矿井水害注浆治理工程中注浆材料优选和配比优化问题,采用单因素试验与响应曲面法(RSM)相结合的方法进行超细水泥注浆材料优化配比研究。首先通过单因素试验对不同水灰比、硅灰(SF)掺量及高效聚羧酸减水剂(PCS)掺量条件下浆液黏度、泌水率及7 d单轴抗压强度进行分析,以确定RSM最佳基准水平,其次构建以浆液黏度、泌水率及7 d单轴抗压强度为响应目标的二次多项式预测模型,结合方差、残差及响应曲面分析各响应变量对响应目标的影响规律,确定注浆材料最优配比。通过单因素试验结果对比分析,发现最优水灰比、SF掺量及PCS掺量分别为1∶1、35%及0.3%。通过RSM研究发现,浆液黏度、泌水率及7 d单轴抗压强度不仅受单一因素影响,且存在多因素交互作用。根据建立的二次多项式响应面回归预测模型可知,当水灰比、SF掺量及PCS掺量分别为0.7∶1、38%及0.2%时,注浆材料性能最优,其回归模拟预测浆液黏度、泌水率及7 d单轴抗压强度分别为210.82 mPa·s、1.0%及12.22 MPa。通过室内试验,其结果与预测模型结果吻合度较高,进一步验证了模型的可靠性,证明了该模型能够用于注浆材料优化配比设计研究。

生物质混凝土在岩石表面增肥的研究

提出了人工提高岩面粗糙度,以提高其承载土壤能力,再结合客土喷播技术的岩面复绿方法。首先,在研究泥浆流动性的基础上,建立了岩面承载土壤能力的测量方法。然后分别利用水泥砂浆平铺、水泥砂浆微台阶、桔杆水泥砂浆微台阶法改造了岩面,并研究了改造后的岩面的承载土壤能力。结果表明水泥砂浆平辅法由于提高了岩面粗糙度而提高了承载土壤能力,水泥砂浆微台阶法由于岩面外形的改变为承载土壤提供了条件,因而大幅提高了承载土壤能力,桔杆水泥砂浆微台阶法不仅保留了水泥砂浆微台阶的优点,还由于桔杆的加入,形成了尖锐的突出物,能够留存树叶、杂草等从而进一步提高了岩面保持土壤、水分和肥力的能力。最后,提出了标准承载土壤能力的概念,解决了不同浓度泥浆测试结果不同的问题。

基于声发射频谱的次生胶结岩体加卸载损伤特性

斜坡岩体裂隙中广泛存在后期次生胶结物,地震过程中次生胶结岩体极易发育密集微裂纹。开展单轴静荷载和加卸载试验,通过声发射频谱演化特征研究荷载条件下次生胶结物对岩体微裂纹扩展过程的影响。研究结果表明:静荷载下小尺度裂纹、微小裂纹、沿晶裂纹和穿晶裂纹贯穿整个试验过程,低频高频信号对应的大尺度裂纹主要产生在不稳定扩展阶段,加卸载条件下声发射主频演化类型受到次生胶结物面积的影响,次生胶结物对岩体损伤起主要控制作用,降低了造成岩体损伤的应力阈值,加卸载作用下次生胶结物与岩石性质差异造成的非协调变形是造成损伤的根本原因。

水泥基3D打印技术在岩石力学教学实验中的应用

该文将水泥基3D打印技术应用到岩石力学教学实验中,采用水泥基3D打印技术制作类岩石力学试样,不仅能降低实验成本,还可融入增材建造、混凝土材料和岩石力学等课程专业知识,丰富了实验教学内容,提高了教学质量。该实验让学生自主选择打印材料、设计打印模型、优化打印路径,最后打印制作出类岩石力学试样,并完成岩石力学实验。整个实验过程有助于增强学生的学科交叉知识运用能力和动手能力,培养创新思维和科学素养。

不同灰砂比岩充组合体疲劳损伤与破裂特性试验研究

为了揭示地下采场中岩充组合结构体在频发应力扰动作用下的损伤演化和破裂机制,对4种不同灰砂比的岩充组合体试样开展多级增幅疲劳试验并进行试验后CT扫描。结果表明:(1)充填体的灰砂比对岩充组合体的变形、刚度劣化、损伤扩展和破坏模式均有影响。灰砂比从1:4下降到1:12,体积膨胀增加,割线模量先增加后减小。(2)提出了基于不可逆轴向应变的累积损伤演化模型,该模型与试验数据拟合良好,灰砂比为1:4和1:8的岩充组合体累积损伤呈现2阶段增加模式,即最初稳定增加,随后急剧增加。灰砂比为1:10和1:12的岩充组合体呈现倒“S”形损伤累积模式,即初始、稳定和加速增加3个阶段。(3)随着灰砂比减小,岩充组合体的宏观破坏模式从拉伸−剪切混合破坏过渡为拉伸破坏。试验后的CT图像揭示了岩充组合体细观破裂演化模式,包括充填体中的剪切破坏、沿着岩石和充填体接触面的拉伸破裂以及岩石中的拉伸和剪切破裂。采用“柔性充填体”有利于防止岩石剥落、坍塌等灾害。研究成果可为矿山充填配比优化和深部矿产资源安全开采提供理论依据。

不同加载速率下废石胶结充填体的力学特性及破裂特征研究

为研究不同加载速率与骨料粒径级配对废石胶结充填体的力学特性以及破裂特征变化规律;对不同骨料粒径级配的废石胶结充填体进行不同加载速率的单轴压缩试验,分析其力学特性的变化规律;并辅以声发射系统,研究废石胶结充填体内部裂纹的发展演化规律。结果表明:废石胶结充填体的单轴抗压强度与弹性模量随着加载速率的增大呈线性增长趋势;废石胶结充填体的单轴抗压强度与弹性模量随着骨料级配指数的增大呈现先增长后降低的趋势;随着骨料级配指数和加载速率的增大,试样破坏模式由张拉破坏逐渐转变为剪切破坏,破坏程度加剧,完整度降低;试样内部裂纹的发展演化总体分为压密阶段、弹性阶段、稳定扩展阶段及非稳定扩展阶段。

河南某水泥用灰岩矿山废石综合利用试验研究

河南某水泥用灰岩矿废石为剥离的顶板高MgO白云岩,总量达6000余万吨。为评价其综合利用方向,本文通过实验室流程试验,对废石开展综合利用研究。通过试验得出:废石放射性指标内照指数(I_(Ra))0.12、外照指数(I_(γ))0.13,饱和抗压强度平均值61.81MPa,碱活性反应膨胀率平均0.090%,坚固性平均值7.49%,压碎指标平均值13.87%,各指标均满足Ⅱ类建筑用石料质量指标要求,可作为建筑用石料综合利用。该研究为同类水泥用灰岩矿山废石综合利用提供了方向。

弱胶结地层富水巷道围岩变形规律研究

新疆煤系地层以弱胶结地层为主,弱胶结岩石普遍具有胶结松散、力学强度低和水软化作用明显的特点,弱胶结地层给煤炭资源开采带来极大困难。结合新疆弱胶结地层地质条件,采用相似模拟实验方法,分析了膨胀应力在此类巷道围岩变形过程中的影响,研究了弱胶结地层富水巷道围岩变形规律,为西部矿区类似工程地质条件下巷道变形规律研究与工程支护设计提供有益的参考。

干热岩超高温防衰退水泥浆体系及应用

干热岩长期高温导致水泥石强度衰退,易造成套管挤毁或窜流,严重影响钻井的安全。针对200℃以上常规加砂水泥石强度衰退难题,基于硅铝键结合增强效应,通过优化水泥物相组成,开发了超高温增强材料SCKL,可以满足210~300℃下固井要求,不仅抑制了水泥石强度衰退,且促进了水泥石强度长期发育,300℃、48 h的抗压强度为18.2 MPa,30 d抗压强度高达23.2 MPa,探索了超高温增强材料对水泥石微观结构的影响,揭示了超高温水泥石微观作用机制。研选了温度广谱型缓凝剂,开发了大温差防衰退水泥浆体系,可以满足干热岩100℃温差下安全固井需求,并在青海共和盆地成功应用5口井,固井质量均为优质,为干热岩井筒水泥环密封完整性提供了安全保障。

伊犁矿区弱胶结覆岩导水裂缝带发育高度探测

以伊犁四矿23223工作面为研究对象,分别采用地面瞬变电磁法的导高探测、井下钻孔并行电法的导水裂缝带高度探测,以及数值模拟等方法对煤层开采上覆岩层导水裂缝带发育高度及规律进行了现场探查与研究。结果表明:弱胶结覆岩条件下,工作面垮采比为3.0,裂采比为5.3。研究结果能进一步为弱胶结覆岩下采动安全开采提供科学借鉴。

盐岩蠕变特征对井筒形变量的影响规律

针对盐岩地层普遍出现的套损现象,借助三轴岩石力学实验对取自川东北油气田某地层段盐岩的蠕变特性进行了实验研究。基于实验结果,构建了可描述盐岩的衰减蠕变阶段和稳态蠕变阶段特征的非定常盐岩蠕变模型,基于该盐岩蠕变模型计算深部盐岩地层蠕变过程中井筒径向位移的变化,计算结果显示井筒内压能有效地降低盐岩内壁的蠕变位移,而地层水平主应力和上覆地层压力可增大地层的偏差应力,从而增加盐岩内壁的蠕变位移。为避免盐岩蠕变造成套管变形,在水泥中添加空心陶瓷颗粒可有效降低水泥的弹性模量,使得水泥环能充分吸收地层径向蠕变给井筒系统增加的应变能,进而降低对套管的挤压作用,减小套变风险,形成油气井工程上一种新型套管止变技术方法。

软破矿岩条件下胶结充填法转分段崩落法研究及应用

金川集团龙首矿西二采区上部中段充填采场发生失稳事故后,采矿方法由下向分层进路式胶结充填法转为无底柱分段崩落法时,面临着软破矿岩条件下覆盖层形成和采场稳定性问题。采用数值计算和现场试验等方法,对这2个关键技术问题进行了研究。数值模拟结果表明,随着崩落法首采分段回采工作的进行,采场复合顶板经历了破坏裂纹萌生、零星散块冒落、拱形批量冒落和柱塞状整体冒落等阶段,当首采分段回采结束时,顶板复合岩层冒落能够为崩落法采场提供足够厚度的覆盖层,且在崩落法采动地压下软破矿岩采场能够保持稳定。现场工业试验表明,在崩落法采场首采分段采用“阶梯式退采均匀扩展采空区+总量控制出矿”的技术方案,能够安全、高效地形成覆盖层,并通过增补“钢拱架+钢筋网+锚杆”的技术方案,解决在崩落法采动地压下维持破碎矿岩采场稳定性的问题,为无底柱分段崩落法在西二采区的扩大应用奠定了技术基础。

废石颗粒级配优化对充填材料性能的影响机制

目的:减少排土场废石堆积对矿山产生的安全威胁。方法:通过研究废石颗粒粒径分布特征,进行不同级配废石胶结充填材料的力学特性及流动性能实验,优化废石颗粒级配,揭示其与水泥及粉煤灰固化作用机制。结果:+0.075~-16 mm废石充填体试件的颗粒级配分布特征与机制砂充填体强度特性相近,其单轴抗压和抗拉强度及软化系数均高于其余废石级配充填体;四种充填料浆的坍落度相差不大,而+0.075~-16 mm废石充填料浆的泌水率较小,流动性较好;养护28 d废石(+0.075~-16 mm)充填体试件表面较平整,微观结构较紧密,其内部被少量的废石颗粒和粉煤灰、较多的网络状水化硅酸钙(C-S-H)凝胶和大量的针棒状钙矾石(AFt)水化产物,以及六方板状的CH晶体结构充填,使得其微观结构比其余废石(-16 mm和+0.15~-16 mm)试件更加致密,与机制砂(-16 mm)试件相接近。结论:既能为类似矿山优化充填工艺参数提供技术借鉴,也可以减少矿山充填开采成本。

胶结面缺陷对堆石混凝土抗压强度影响

堆石混凝土(rock-filled concrete, RFC)独特的施工技术导致其缺陷与传统混凝土不一样。通过物理试验与真实破坏过程分析(realistic failure process analysis, RFPA)数值模拟探讨了堆石混凝土中堆石与自密实混凝土(self-compacting concrete, SCC)胶结面缺陷及自密实缺陷对其抗压性能的影响。结果表明:随着缺陷数量的增加,堆石混凝土的无侧限抗压强度下降。同等缺陷数量下,胶结面缺陷试件的抗压强度低于自密实缺陷试件。同时,声发射分析显示,胶结面缺陷试件破坏所需能量更低,表明胶结面缺陷对材料力学性能有更为显著的负面影响。这些发现为理解和改善堆石混凝土结构设计与耐久性提供了重要参考。