超大粒径人工砾石土的击实特性试验研究

对2种击实功、3种击实尺寸、8种掺砾量的人工砾石土进行击实试验,研究人工砾石土颗分曲线、最优含水率、最大干密度、破碎率、细料变化等特性。得出尺寸效应、骨架作用、掺砾量、击实功是人工砾石土击实特性的关键影响因素。人工砾石土在击实功能的作用下颗粒级配趋于良好,其最优含水率均随人工掺砾石量的增加而降低,破碎主要发生在粒径大于约为最大粒径的0.5倍的颗粒范围内。当掺砾量小于60%时,采用2 690 kJ/m3功能300型击实对超大粒径人工砾石土进行质量控制是完全合适的。对于超大粒径人工砾石土的压实度检测,采用粒径小于20 mm的颗粒更能反映击实料的细料变化。     

砾石土击实特性影响因素及现场质量控制研究

粘土作为土石坝防渗料具有悠久的历史,砾石粘土或掺砾粘土作为防渗体有相当的优势,因此快速发展并广泛推广应用。掺砾粘土作为心墙防渗体一般以室内击实试验成果作为参考,因此拟以两河口水电站为工程背景研究砾石土的相关击实特性及现场碾压控制,着重研究分析击实仪器尺寸影响、击实密度与击实功能规律、现场碾压与室内击实对应性、现场不同粒径砾石土压实控制标准。经过系统性试验,总结了这些因素影响的规律,并为以后的砾石土防渗体填筑控制提供参考。     

砾石土的击实特性及最大干密度试验研究

分析认为,砾石土的击实最大干密度与土料母岩性质、风化程度、P5含量、击实功能等因素关系密切,增大试验仪器尺寸可提高砾石土的最大干密度,在试验条件允许时宜尽可能选用较大尺寸击实仪。砾石土全料击实最大干密度、最优含水率与细料的击实性关系密切并具有良好的归一性。提出了一种计算砾石土最大干密度的经验公式,与常规试验方法所得结果相比,各项指标偏差完全在试验规程允许误差范围内。本方法简捷、快速、经济实用,可满足高强度大方量施工进度质量控制要求,同时能考虑每个测点土料压实性变化。该方法已成功应用于大坝填筑质量检测,良好效果。研究成果可供类似工程的质量控制推广应用。     

宽级配砾质土压实特性试验研究

宽级配砾质土随粗料含量变化呈现出悬浮–密实、密实–骨架和骨架–空隙3种不同结构,因而表现出不同的压实特性。依据等量替换法剔除超径颗粒后,对糯扎渡堆石坝心墙料的不同掺砾量的宽级配砾质土进行了重型击实试验,研究了宽级配砾质土在不同粗料含量、不同结构下的压实特性,并对击实作用下颗粒破碎规律进行了分析。试验结果表明:随掺砾量或粗料含量的增大,最大干密度呈先升后降的变化趋势;击实后颗粒破碎随粗料含量的增大而增加。     

不同掺砾量下砾石土抗拉强度试验研究

砾石土的抗拉强度是土心墙堆石坝抵抗拉裂破坏的重要指标之一。基于自主研制的单向拉伸试验模具,对不同掺砾量下的砾石土进行了系列的单向拉伸试验。在此基础上得到了以下结论:在本文的试验参数范围内,砾石土的抗拉强度随着含水率的增大而减小,随着干密度的增大而增大;分别给出了各掺砾量下土样抗拉强度与其最优含水率及最大干密度的关系表达式;对于处于各自最优含水率和最大干密度下的砾石土,掺砾量从0%增加到50%时,试样的抗拉强度从122.6 kPa减小到了49.8 kPa,且两者呈线性递减关系;试样的峰值拉应变和极限拉应变均随着掺砾量的增加而线性递减;对不同掺砾量土样的断裂能分析发现,随着掺砾量的增加,土样的抗拉能力不断减弱;在略高于最优含水率及处于最大干密度时砾石土试样的综合抗拉能力最强。相关试验成果可为实际土石坝心墙抗裂设计提供参照。     

全-细颗粒关系模型的砾石土心墙压实度快速检测技术研究

通过对砾石土心墙坝全料压实度与不同击实功下细料压实度之间关系的分析研究,得出两河口工程砾石土心墙料不同击实功能下细料与全料压实度之间的匹配关系,从而寻求到快速检测的手段。     

珊瑚礁砾石土压实特性试验研究

以三亚地区珊瑚礁砾石土为路基填筑材料,采用室内试验手段,开展现场均匀级配下钙质砂及礁岩碎屑物(含砾块)混合料的击实试验,分析击实层数和击实功对填料压实效果的影响,对珊瑚礁碎屑沉积物的路用潜能作出评价,并优化其填筑工艺。     

掺砾改性砾石土心墙料的应力应变特性研究

结合采用掺砾改性砾石土作心墙料的某水电站项目,通过高压大型三轴试验,对心墙防渗料的应力应变特性进行了研究;给出了E-μ模型参数和原成都科大简化K~G模型参数,为工程决策提供依据。结果表明,该砾石土为工程特性良好的土石坝心墙料,掺砾改性是一种极具工程实践意义的技术手段。     

聂庆科;王英辉;田鹏程;梁书奇;

通过击实试验和击实后土样的压缩和剪切试验研究红黏土的变形和强度特性。研究表明:重塑土的最大干密度比原状土的最大干密度大,而重塑土的最优含水率则比原状土的最优含水率小;随击实功增大,土样的干密度增大,而最优含水率减小;含水率稍高的击实土样的水稳定性要比含水率稍低的击实土样的水稳定性好;当含水率较大时,击实土样的相对固结变形量较大,固结稳定并浸水再固结后,原来含水率较小土样的变形增量反而稍微大些。     

不同土石掺配比例对土石混合料的力学及渗透特性影响试验研究

将细粒土与碎石含不同比例掺配后进行了击实试验及击实后的力学、渗透试验，随着土石掺配比的增加，土石混合料的最大干密度将随着增加，最优含水率随之减小。在击实状态下，随着砾石掺配比的增加，土石混合料的抗剪强度增加，压缩压缩模量增大，渗透性有所增加。混合料出现上述工程特性的原因是随着土体中砾石含量的增加，土中的砾石颗粒逐渐形成骨架，细粒土填充在骨架中，所形成的土体结构在受剪时颗粒之间相互接触、咬合嵌套，增强了抗剪强度，降低了压缩性，同时由于土体中形成了更多的空隙，渗透性有所增加。     

Experimental study of the effect of fines content on dynamic compaction grouting in completely decomposed granite of Hong Kong

This paper addresses the effects of fines contents on the mechanical behavior of CDG (completely decomposed granite) during dynamic compaction grouting. The first set of tests involved adding different amounts of kaolin clay into CDG to study the effects of fines contents on the compaction characteristics, permeability, consolidation behavior and shear strength of soils. It is found that, as the fines content increases, the dry density decreases, however the optimum water content increases. In addition, the permeability decreases due to reduction of void ratio, and the coefficient of consolidation increases with higher fines content. Furthermore, with increasing fines contents, the shear stress tends to be constant after it reaches the peak strength. However, when reaching the peak value, the shear stress reduces with further adding of fines content. In the second set of tests, the dynamic compaction grouting tests are carried out to study the effect of fines content on the compaction efficiency of Hong Kong CDG. It is found that, the compaction efficiency increases with increasing fines content, and reaches the peak compaction efficiency when the fines content reaches 6%, and then the compaction efficiency drops abruptly from a peak value of 0.55–0.25 when the fines content increases from 6% to 8%. However, when the fines content increases from 8% to 41%, the compaction efficiency decreases very slowly.     

土石混合料最大干密度试验研究

在开发了大型击实仪的基础上,研究了不同最大粒径及粗颗粒含量时土石混合料最大干密度和最佳含水量的变化规律,试验结果表明,粗颗粒含量对土石混合料的最大干密度影响较大,最大粒径变化时,土石混合料的最大干密度和最佳含水量变化规律不明显。     

Effects of particle shape and size distribution on the shear strength behavior of composite soils

The effects of particle shape and size distribution on the constitutive behavior of composite soils with a wide range of particle size were investigated. Two comparable sets of specimens were prepared: (1) mixtures of fines (clay and silt) and an ideal coarse fraction (glass sand and beads), and (2) mixtures of fines and natural coarse fraction (river sand and crushed granite gravels). Direct shear box testing was undertaken on 34 samples and the structure of the shear surfaces, change in volume and water content and the particle shape coefficient of the sheared specimens were examined. The results indicate that the contraction/dilation a specimen exhibits is restrained within the shear zone while the outer zones remain unchanged during shearing. An increased coarse fraction leads to an increase in constant volume shear strength. In addition, increasing elongation or decreasing convexity of the coarse fraction increases the constant volume friction angle. The overall roughness of the shear surface at constant volume state is negatively related to particle smoothness (convexity) and positively related to the area of the shear surface occupied by particles with particular shapes. Two equations are proposed for the estimation of constant volume friction angle based on the proportion and shape coefficient of the coarse fraction. It is hoped this will assist in considering the shear strength of mixed soils when the size of the coarse fraction makes laboratory testing difficult.     

Particle breakage of sand subjected to friction and collision in drum tests

This paper presents a laboratory experimental study on particle breakage of sand subjected to friction and collision,by a number of drum tests on granular materials(silica sand No.3 and ceramic balls)to investigate the characteristics of particle breakage and its effect on the characteristics of grain size distribution of sand.Particle breakage increased in up convexity with increasing duration of drum tests,but increased linearly with increasing number of balls.Particle breakage showed an increase,followed by a decrease while increasing the amount of sand.There may be existence of a characteristic amount of sand causing a maximum particle breakage.Friction tests caused much less particle breakage than collision tests did.Friction and collision resulted in different mechanisms of particle breakage,mainly by abrasion for friction and by splitting for collision.The fines content increased with increasing relative breakage.Particle breakage in the friction tests(abrasion)resulted in a sharper increase but with a smaller total amount of fines content in comparison with that in the collision tests(splitting).For the collision tests,the fines content showed a decrease followed by an increase as the amount of sand increased,whereas it increased in up convexity with increasing number of balls.The characteristic grain sizes D₁₀ and D₃₀ decreased in down convexity with increasing relative breakage,which could be described by a natural exponential function.However,the characteristic grain sizes D50 and D60 decreased linearly while increasing the relative breakage.In addition,the coefficients of uniformity and curvature of sand showed an increase followed by a decrease while increasing the relative breakage.     

大型击实试验研究初探

本文用自制的大型击实仪对大粒径碎石土作了试验研究 ,得出了碎石粒径 6 0 mm以下 ,碎石含量为 2 5 %～ 5 5 %情况下碎石土最大干密度与最佳含水量的试验结果 ,对大粒径碎石土填方质量控制有重要意义     

废弃橡胶轮胎环箍的散体材料特性研究

为了提高废弃轮胎路基使用性能和效果,研究了废弃轮胎环箍下的散体材料压实度和承载力。由于轮胎的侧限作用,轮胎内粉质黏土的最佳含水量比标准实验测定的最优含水量大,细砂的小于最优含水量。轮胎内散体材料的压实度一定范围内随着压实功的增加而增加,级配均匀的砂土在相同压实功的条件下干密度最高,取得最优的压实效果。轮胎的半径越大承载力越低;粗骨料填充的轮胎比细骨料填充的轮胎承载力高,但变形大。轮胎新旧对其内填散体材料的压实度和承载能力没有影响。由于散体材料的横向变形受到轮胎的约束,处于三向受压状态,因此提高了竖向载荷能力。     

粗粒土最大干密度理论计算方法研究

通过引入细粒料最大干密度的校正系数及粗粒土的密度干涉系数和最佳含水量系数,在室内大型击实试验的基础上建立密度干涉系数及最佳含水量系数与粗颗粒含量之间的双对数关系,从而得出了粗粒土最大干密度和最佳含水量的理论计算公式。     

高掺量磷石膏稳定红黏土胀缩特性

为研究高掺量磷石膏稳定红黏土胀缩变形特性,改变以往磷石膏和水泥作为外掺固化剂改良土的研究思路,把磷石膏和红黏土作为主要原材料,以水泥含量5%,磷石膏和红黏土比例1∶1、1∶2、1∶3的配比制作试样,研究不同含水率、不同压实度下素红黏土和磷石膏稳定红黏土胀缩变形特性。结果表明：素红黏土绝对膨胀率在0～3 h线性增加,3 h后基本达到稳定;磷石膏稳定红黏土绝对膨胀率在0～3 h缓慢增加,变形量小于素红黏土,3 h后变形量持续增加,在2 d左右超过素红黏土,表现出更大的膨胀性,膨胀稳定时间为10 d左右;磷石膏水泥稳定红黏土混合料绝对膨胀率相较于素红黏土膨胀变形具有滞后作用,磷石膏和水泥的掺入可以有效降低混合料前期的膨胀变形,且同一含水率条件下,磷石膏掺量越低,绝对膨胀率越大;磷石膏稳定红黏土初始含水率越低,绝对膨胀率越大;磷石膏稳定红黏土和素红黏土线缩率随含水率、压实度的增大而增大;水平收缩率随含水率的增大而增大,随压实度的增大而减小;相同含水率和压实度下,磷石膏水泥稳定红黏土线缩率大于素红黏土,水平收缩率小于素红黏土;高掺量磷石膏稳定红黏土7 d龄期无侧限抗压强度能够满足规范对二级及以下...     

Evolution granulométrique des sols sablo-argileux soumis à des compactages dynamique et statique

The compaction of a quartz sand by the modified Proctor test involves the production of fines produced by the breaking of the grains of the sand. This production of fines is measured by the grain size analysis before and after compaction. The adding of clay to the sand diminishes the evolution of the grain size. The process is proportional to the quantity of clay added to the sand. If the dynamic compaction of the Proctor test is substituted by the static compaction, one notes the same occurrences: static or dynamic compaction breaks the grains of sand and the clay added to the sand protects the grains from the breaking induced by the compaction stresses.