煤矸石喷射水泥在喷射混凝土工程中的应用

对煤矸石喷射水泥在喷射混凝土工程中的工程特性包括力学性能及收缩性能进行了试验研究,实验表明采用它配制的喷射混凝土不仅具有速凝、早强特性,而且28d强度也较高且具有微膨胀性;对煤矸石喷射水泥的早期强度高且后期强度稳定发展以及微膨胀机理也进行了探讨。     

循环荷载作用下掺土煤矸石力学性状试验研究

为分析煤矸石中掺土作为高速公路路堤填料的可行性,通过掺土煤矸石的动三轴试验,对掺土煤矸石在循环荷载作用下的动力特性进行试验研究.研究结果表明:在煤矸石中掺入适当比例的黏土,其强度均有不同程度的提高,其中以煤矸石与土的干质量为3∶1～4∶1时效果较为明显;掺土煤矸石的动应力-应变骨干曲线可采用双曲线拟合,得出4种试验煤矸石样的等效非线性动力本构H-D模型参数.试验结果可用于分析煤矸石路堤在交通荷载作用下的稳定性及变形性状.采用掺土煤矸石作为路基填料,其力学性能完全满足高速公路的设计要求.     

煤矸石抗剪强度特性试验对比研究

为了分析不同时期排弃的煤矸石力学特性的差异性,以现场固结煤矸石样本筛分级配为试验级配进行不同试样含水率条件下固结煤矸石与新排弃煤矸石的室内对比直剪试验。试验结果表明,与新排弃煤矸石试验曲线均呈应力硬化现象不同,固结煤矸石在试样含水率较小时试验剪应力–剪位移曲线存在相对突出的峰值,呈明显应变软化现象。而随着试样含水率增大,固结煤矸石的黏结性特性得到呈现,应力–应变关系也渐变为应变硬化。试样干密度与试样含水率对固结煤矸石和新排弃煤矸石抗剪强度参数的影响不同,干密度对固结煤矸石黏聚力以及新排弃煤矸石内摩擦角的影响更为显著。而相对于新排弃煤矸石,固结煤矸石内摩擦角对试样含水率更为敏感,至饱和含水率时固结煤矸石抗剪强度主要由黏聚力提供,而新排矸石内摩擦角值降低的幅度则不到15%。试样含水率对固结煤矸石及新排弃煤矸石抗剪强度影响的差异与矸石组成中细颗粒组成成分相关。试验成果可为煤矸石山的稳定性计算提供依据。     

煤矸石压缩试验的颗粒流模拟

 根据煤矸石颗粒材料的特点,采用三维颗粒流方法PFC3D的接触连接本构模型模拟煤矸石的压缩特性,再现其复杂的非线性本构关系。设计单一级配和泰波理论级配方案,并用Fish语言生成级配颗粒模型。对煤矸石的三轴压缩试验过程进行数值模拟,比较不同围压下的应力–应变曲线、体积应变曲线和微裂纹发展曲线,从细观角度验证不同级配煤矸石试样的强度及变形规律。研究结果显示,优化的级配方案能提高矸石的峰值强度,降低其压缩量,这对优化矸石充填的级配设计有一定的参考价值。     

煤矸石的强度特征试验研究

通过中型三轴试验及现场大型直剪试验对煤矸石的强度特性进行了系统研究，得到了煤矸石强度包线的形式和参数以及煤矸石抗剪强度随粗颗粒（粒径D〉5．0mm）含量的变化规律，并对试验中最大主应力差及颗粒破碎量进行多元统计分析，得到围压、孔隙比及粗料含量的变化规律。     

煤矸石-土工格栅-砂层状体系的界面摩擦特性试验研究

结合工程实践提出煤矸石-土工格栅-砂层状体系的加筋土结构,通过直剪试验和拉拔试验,测试不同法向应力下煤矸石-土工格栅-砂层状体系的筋土界面特性,并与常规加筋土结构的筋土界面特性进行对比。研究表明:层状加筋体系具与有常规加筋土体系相似的界面特性,但由于砂的充填作用,提高了加筋层的密实度,增大了筋土接触面,使筋土界面强度更高,且界面强度发挥更早;层状加筋土体系还可以为加筋煤矸石提供排水通道,避免煤矸石浸水软化。     

煤矸石喷射水泥基层材料的路用性能与机理分析

煤矸石喷射水泥可加速公路施工速度,减少路基收缩。对煤矸石喷射水泥路基材料分别进行了强度试验和收缩性能试验研究。结果发现煤矸石喷射水泥路基材料与普通水泥路基材料相比,其早期抗压强度显著提高,干燥收缩和温度收缩均显著减小。针对煤矸石喷射水泥路基材料所表现出来的这些特性,还对其产生的机理进行了探索与分析。     

煤矸石混合料劈裂强度试验研究

将邯邢地区某煤矿煤矸石与粉煤灰、石灰粉混合,配制成煤矸石混合料.对混合料的劈裂强度进行试验研究,根据均匀设计原理,设计出10组煤矸石混合料的试验配合比方案,并对不同配合比下煤矸石混合料进行试验.利用回归分析模型对试验结果进行分析,建立了煤矸石混合料劈裂强度与各掺和料掺和量之间的回归方程.通过回归方程分析出粉煤灰、石灰粉掺量对煤矸石混合料劈裂强度的影响.     

煤矸石混凝土抗折强度试验研究

以榆神矿区煤矸石为粗骨料,通过288个棱柱体抗折强度试验,分析了煤矸石含碳量、煤矸石取代率及水灰比对煤矸石混凝土抗折强度的影响.结果表明：当不同矿源煤矸石含碳量由0.91%增加至2.09%时,煤矸石混凝土抗折强度降低了21.1%～32.6%;与普通混凝土相比,不同煤矸石取代率下煤矸石混凝土抗折强度降低了20.5%～47.5%;当水灰比由0.25增加至0.45时,煤矸石混凝土抗折强度降低了8.0%～15.3%.综合考虑了煤矸石含碳量和煤矸石取代率的影响,提出了适用于不同矿源煤矸石混凝土抗折强度的预测公式.     

煤矸石粗骨料对混凝土力学性能的影响

针对煤矿煤矸石产量大、利用率低等问题,对煤矸石作为混凝土骨料的理化性能和力学性能进行了探究。试验结果表明：与普通碎石相比,非自燃煤矸石的堆积密度与表观密度小、吸水率高、压碎值大,当水灰比不变时,煤矸石混凝土的强度随着煤矸石粗骨料掺量的增加先增加后减小;当非自燃煤矸石混凝土掺量不变时,煤矸石混凝土的强度随着水灰比的增加先增加后减小。水胶比为0.5,煤矸石粗骨料取代率为40%时,煤矸石混凝土的强度最高为最优配合比。煤矸石可以作为混凝土粗骨料使用,但若全部采用煤矸石作为混凝土粗骨料,应限制煤矸石粗骨料在强度要求较高的混凝土中使用。     

岩土材料破损特性的颗粒流研究

基于颗粒流理论,利用颗粒接触胶结本构模型,建立结构性岩土材料的颗粒流模型。通过颗粒流数值模拟试验,对结构性岩土材料破损的细观机理作了初步的研究。试验中采用胶结在一起的小圆盘去代替一个可破碎颗粒,再在可破碎颗粒之间施加适当的胶结,形成结构性岩土材料试样。在试验过程中通过记录胶结破损的数目和空间位置,就可以直观反映结构性岩土材料破损特性。试验表明试样在低围压下压缩试验中应力应变曲线表现为软化型,伴随剪切带的形成,有必要区分体积破损率和面积破损率。试样在高围压下压缩试验应力应变曲线表现为硬化型,没有明显的剪切带形成,表现为体积破损。分析表明颗粒流方法是研究岩土材料破损特性的一个有力工具。     

颗粒破碎对砂土剪切性质影响的离散单元研究

采用离散单元方法,建立了圆形颗粒、不破碎非圆形颗粒和破碎非圆形颗粒的数值试验模型,进行了砂土的双轴剪切试验,研究了颗粒破碎现象对砂土物理力学性质的影响,分析了颗粒破碎和颗粒形状对试样强度的影响以及围压对颗粒破碎性质的影响。研究结果表明：颗粒破碎现象严重影响砂土的峰值强度以及体积应变性质,并且低围压下颗粒形状对强度影响大于颗粒破碎,随着围压增大,颗粒破碎的影响逐渐增强;围压影响颗粒破碎发生的速率和最终的破碎率;由对颗粒破碎的位置和试样内位移场的追踪可得到颗粒破碎的细观演化规律及破碎带的分布范围,破碎带分布范围与围压有关。     

某商住楼煤矸石多孔砖的酥裂分析及处理

某商住楼工程投入使用后，南北外墙出现大量横向裂缝，多孔砖出现酥碎现象。通过现场调查，发现问题源于煤矸石多孔砖发生石灰爆裂。就此问题，从烧结砖材料成分、化学反应条件及结构破坏机理等方面进行了分析，提出预防措施和具体处理方案。     

DEM analysis of energy dissipation in crushable soils

It is well known that particle crushing plays a critical role in the mechanical behavior of granular soils. Understanding energy dissipation under the influence of particle breakage is of key importance to the development of micromechanics-based constitutive models for sands. This paper reports the original results of the energy input/dissipation of an idealized crushable soil using 3D DEM simulations. Particle breakage is modeled as the disintegration of the synthetic agglomerate particles which are made up of parallel-bonded elementary spheres. A parametric study is performed to fully investigate the effects of initial specimen density and crushability on the energy allocation of the crushable soil.The simulation results show that the initial specimen density and the crushability strongly affect the energy allocation of the soil both at small and large strains. The major roles of particle breakage, which itself only dissipates a negligible amount of input energy, are to advance changes in the soil fabric and to promote the interparticle friction dissipation. Particularly, at small strains, particle breakage disrupts the strain energy buildup, and thus, reduces the mobilized shear strength and dilatancy of a granular soil. At large strains, where particle breakage is greatly reduced, steady energy dissipation by interparticle friction and mechanical damping is observed. Furthermore, it is found that shear bands develop in most dense crushable specimens at large strains, but they are only weakly correlated to the anisotropy of the accumulated friction dissipation.     

Fenay Beck Flood-Alleviation Scheme

The paper describes flood detention and channel improvement schemes which have been designed to alleviate the flooding of domestic and industrial properties to a 50-year standard of protection. Landscape architects were incorporated into the design teams to cover environmental aspects.
The flood-detention dam would have been constructed mainly of colliery waste, and the design of the concrete horseshoe spillway and stilling basin was checked using a 1 : 40 physical model. River regulation would be by an automatic vertical gate activated by downstream water levels.
Following planning refusal, a channel-improvement scheme was adopted, which is presently under construction. Reduction in valley storage increased downstream flows, necessitating the enlargement of an old brick and concrete culvert within the ICI works to ensure that there were no detrimental effects within their boundary. An increased benefit/cost ratio of 3.46, as compared with 2.55 obtained for the detention scheme, was partly due to the application of new standards.     

EVALUATION OF PARTICLE CRUSHING IN SOILS USING X-RAY CT DATA

The objective of this paper is to evaluate particle crushing in the soil using the results of X-ray CT scanning without any destruction and sampling. First of all, the properties of X-ray CT data are discussed using its statistical consideration. Then, a method for evaluating particle crushing is proposed. This method is implemented by scanning simple granular materials using aluminum rods and soil. Then, a series of model pile loading tests are conducted for the materials of non-crushable and crushable soils. Based on the results of CT scanning for the model grounds, the effectiveness of the proposed method for evaluating particle crushing using X-ray CT data is confirmed. Finally, one of the effective usages of X-ray CT data in geotechnical engineering is convinced.     

Deformation and Crushing of Particles of Cement Treat Granulate Soil

Cement Treat Granulate Soil (CTGS), a new artificial granular material, has been developed recently by mixing the dredged marine clay with appropriate amounts of cement and polymer. The CTGS particles are crushable and deformable, thus forming a compressible material. Besides being a lightweight material, CTGS is a granular material, and is therefore expected to be applied in reclamations or as a back fill or subsoil materials. This study investigates the deformation and crushing of the CTGS particles and their effects on the stress-strain behaviors. The comprehensive investigation of the principle of treatment, the micro-structure of particles, triaxial stress-strain behaviors, induced particle crushing and particle deformation are first presented via the experimental work done on two types CTGS produced from a lean-mixture design of cement and polymer. Subsequently, the results of X-ray Computer Topography (CT) scanners along with triaxial CD tests on CTGS and conventional gravel having rigid particles are presented. The test results reveal local failure mechanisms between the individual particles of the CTGS and gravel, from which the failure models of the granular materials formed by deformable and crushable grains and non-crushable grains are interpreted.     

Bearing capacity of surface circular footings on granular material under low gravity fields

Low gravity fields have been simulated through magnetic acceleration to conduct experimental study on bearing capacity of circular footings on a type of crushable planetary regolith simulant,which has comparable density and particle size distribution of lunar soil.The load-settlement responses of surface spread footings are obtained by investigating the relative density,footing size and gravity effects.Applying the hyperbolic asymptote method,normalised foundation stiffness and ultimate bearing capacity are obtained by curve fitting and predicted by power functions using multivariate nonlinear regression.The results show that the nonlinear gravity effect is not negligible,related to stress condition,soil dilatancy and mobilised friction angle.A cone penetration test(CPT)-based method for prediction of bearing capacity is proposed with correlations between ultimate bearing capacity of footings and shallow penetration stiffness of CPTs,avoiding the uncertainties of soil property estimations.Analyses of allowable bearing capacity and footing influence zone in consideration of footing size and gravity effects could therefore improve the design of shallow foundations on the Moon and Mars,and provide new understandings and potential implications to the bearing capacity of shallow foundations on crushable granular material in both terrestrial and extraterrestrial geotechnical engineering.     

A bounding surface plasticity model for highly crushable granular materials

A bounding surface plasticity model is presented for crushable rockfills in the framework of the critical state soil mechanics which includes translation of the critical state line due to particle crushing. A translating limiting isotropic compression line is also introduced and incorporated in the model to describe the position and evolution of the bounding surface. A particle breakage index is introduced as a function of stress invariants which controls the translation of the critical state and limiting isotropic compression lines. The performance of the model is demonstrated using the results of experimental tests on different types of rockfill materials conducted under both monotonic and cyclic loading conditions. The study shows the capability of the model in capturing the characteristic features of the behavior of rockfill and other crushable materials such as ballast and coarse gravel under both conventional and complex loading paths.     

Substrate characterisation for a subsurface reactive barrier to treat colliery spoil leachate

Subsurface permeable reactive barriers (PRB) have been used to successfully treat acidic mine drainage in Canada and offer great potential for doing the same in the United Kingdom. A PRB for the treatment of colliery spoil leachate from a site near Newcastle upon Tyne, UK, has been designed. The selection of the reactive media to be used is of paramount importance, with particular reference to permeability and reactivity. A number of reactive media mixtures containing varying proportions of cattle slurry screenings, green waste compost, calcite limestone chips and pea gravel were prepared and their respective permeabilities and reactivities were investigated. Media mixtures containing 50% 10 mm grade calcite limestone chips showed better alkalinity addition and metals removal than a blank containing 50% pea gravel. A media mixture containing 50% limestone chips and 50% green waste compost showed a 24 h period to achieve maximum addition of alkalinity and maximum removal of acidity and metals. Mixtures containing 25% green waste compost and 25% slurry screenings achieved maximum addition/removal in 4 h. The likely presence of iron sulphide in samples drawn from test vessels during both test runs indicates that bacterial sulphate reduction is occurring in this composite.