水致弱化影响下粉煤灰泡沫混凝土充填体性能试验研究

以普通硅酸盐水泥、发泡剂、粉煤灰和外加剂为原料,制备采空区充填材料.通过试验研究,在不同含水率影响下,充填体的强度特性、应力-应变特性和变形特性.研究结果表明:自由水对充填体力学性能弱化较为明显.具体表现为:随含水率增加,制备的充填体试件抗压强度、抗剪强度递减,前期递减幅度较大,后期较小;充填体峰值强度、峰后残余强度以及延性均随含水率增加而递减;随含水率的增加,弹性模量降低幅度较大,泊松比变化幅度较小,剪切模量和体弹性模量均减小,水弱化影响下充填体会产生进一步压缩.     

基于声发射不同骨料含量胶结充填体损伤过程试验研究

利用RMT-150C型岩石力学测试系统与PCI-2声发射仪,对纯尾砂、骨料质量分数20%及40%三种胶结充填体试样进行单轴压缩破坏声发射监测试验,研究了3种不同骨料含量胶结充填体力学特性以及基于累计声发射事件率的损伤演化特征。试验结果表明:含骨料试样破坏脆性特征更加明显,同时骨料含量的变化在一定程度上影响了胶结充填体承载损伤演化速度,对其承载能力有较大影响;纯尾砂试样与含40%骨料试样在峰值应力前不同阶段均出现不同幅度的声发射活跃现象,可作为矿山充填体声发射监测破坏预警的前兆信息;适量骨料的加入可起到提升充填性能的作用,但声发射事件率作为预警前兆信息则可能失效。     

硫对尾砂胶结充填体强度的影响研究

为探究硫含量对尾砂胶结充填体强度的影响,采用微观结构分析、XRD衍射分析对含硫尾砂胶结充填体的侵蚀机理进行了验证,并通过单轴压缩、巴西劈裂、剪切试验探究了硫含量对各含硫尾砂胶结充填体强度指标的影响规律,结果表明:含硫量的增加导致含硫充填体中石膏和钙矾石晶体成分增加,致使部分C-S-H凝胶分解;随着含硫量的增大,单轴抗压强度和峰值载荷、抗拉强度和峰值载荷、剪切强度和峰值载荷均明显降低,但并非线性变化。     

尾砂粒级组成对充填体强度特性影响的试验研究

分析了5种尾砂的粒级组成和级配关系,对包含尾砂粒级组成在内的3种强度影响因素进行正交试验。研究表明:对充填体强度影响的敏感性顺序为:灰砂比料浆质量分数尾砂粒级组成,但是在灰砂比相同的情况下,质量分数较低的B尾砂试块强度反而较大,因为B尾砂的级配关系最优;适量的细粒级尾砂有助于增加充填体强度,这是由于细粒级尾砂被水泥包裹后填充在大颗粒之间的空隙,促进了颗粒间的胶结,增加了试块的强度;但是当细粒级尾砂过多时导致胶结外膜的含水增多,阻碍了各种颗粒之间的胶结,降低了试块的强度,因此尾砂的粒级组成对充填体强度有明显的影响。     

充填体受压全程应力应变声发射特性研究

利用RMT-150C岩石力学试验系统与声发射监测系统对纯尾砂胶结充填体试件进行了无侧限单轴压缩实验,分析出充填体受压破坏的5个阶段,单轴抗压强度和到达极限强度的应变值,试件受压所能承受的最大应变。发现声发射活动由平静到活跃,最后又趋于平静的现象,在失稳破坏阶段声发射活动最为活跃,探究了声发射活跃的内在原因,同时分析了此阶段大能量事件产生的同时出现短期稳压状态的问题。结合应力应变研究了纯尾砂胶结充填体受压全过程的声发射特性。     

岩溶区地下孔洞多孔充填体的力学性能研究

针对岩溶区地下孔洞充填体的透水性能差、耗材量大等问题，制备了一种岩溶区地下孔洞充填材料，设计一种用于治理岩溶塌陷的多孔充填体结构。为了研究岩溶区径流型孔洞环境下多孔充填体结构的服役性能，对试样进行单轴抗压强度试验，研究不同添加剂配合比和不同养护龄期下充填体的抗压强度变化规律。结果表明：随添加剂配合比的增大，充填体抗压强度呈降低趋势，且28d龄期抗压强度较7d龄期抗压强度降低更明显；充填体抗压强度随养护龄期的增加而增大；当添加剂配合比为1.5%且养护龄期为28d时，充填体的抗压强度最优；多孔充填体结构能保证工程强度要求，还能节约工程材料，有效地解决地下水渗流问题，为治理岩溶区地下径流型孔洞的塌陷提供了思路。     

充填体中全尾砂、江砂和水泥混合材料配比研究

针对某矿选厂的全尾砂硫含量较高,不利于充填体输送的问题,将江砂掺入胶结充填体的骨料中,并按不同的江砂与全尾砂比、灰砂比制备全尾砂、江砂和水泥的混合充填体料浆。通过全尾砂、江砂混合配比的可行性分析、单轴抗压强度试验、沉降性能与脱水性能分析,再结合该矿的充填能力与技术要求,最终确定最佳配比为:江砂与全尾砂比1∶4,灰砂比1∶8,料浆质量分数70%。     

萘系减水剂对不同种类尾砂充填材料性能的影响

根据焦家金矿现有充填工艺,采用全尾砂替代分级尾砂作为充填集料,对比两种尾砂配制成的尾砂充填材料性能的优异,并且研究不同掺量下萘系高效减水剂对尾砂胶结充填料浆沉降速率、泌水率、流动性及充填体强度的影响.结果表明,与粗尾砂相比,全尾砂作为充填集料制成的全尾砂充填料浆具有更优的流动性能和悬浮性能,不易在管道内发生堵塞,且形成的充填体强度较高.萘系减水剂的加入可以降低尾砂充填料浆的沉降速率,改善浆体悬浮性,明显的增加料浆的流动性能,并且提高硬化后充填体的强度.在萘系减水剂掺量为0.3％时,全尾砂充填材料的各项性能均达到最优值.     

腐蚀和养护耦合作用下充填膏体强度演化规律研究

为分析腐蚀和养护耦合作用下充填膏体强度的演化规律,将充填膏体置于两种浓度的NaCl溶液和Na2SO4溶液进行腐蚀和养护,并在各个龄期采用WDW-300型万能试验机进行单轴压缩试验,测试不同龄期充填膏体的单轴抗压强度,在试验基础上分析了强度演化机理,建立了强度演化数学模型.研究表明:在腐蚀和养护耦合作用下,充填膏体的早期强度高于标准养护条件下的强度,随着腐蚀时间的推进,腐蚀溶液中的充填膏体强度逐渐开始低于标准养护,并在达到峰值后进入强度衰减期;NaCl溶液对充填膏体的腐蚀作用较快,而Na2SO4溶液对充填膏体的腐蚀作用较大,建立的充填膏体在腐蚀和养护耦合作用下的强度演化数学模型与试验吻合较好,能够反映充填膏体在腐蚀和养护耦合作用下的强度演化规律.     

不同尾砂级配料浆的优化配比试验研究

为探求某矿尾砂级配料浆的最优配比,调整尾砂原样的粒径组成,并通过三轴剪切试验得到各级配试样的剪切变形、强度特性规律,设计正交试验,分别得到级配组成、料浆质量分数、灰砂比对泌水率、坍落度、抗压强度等的影响关系。结果表明:调整尾砂级配后,各级配试样变形规律大致相同,但峰值强度和残余强度得到明显改善;3个因素对试样泌水率、抗压强度的敏感性排序为:料浆质量分数灰砂比级配,而对坍落度的敏感性排序为:灰砂比级配料浆质量分数。考虑矿体的深部力学环境和经济因素,最终确定该矿充填体料浆的最优配比为:粒径0.15~0.30mm占16.7%,0.30~0.50mm占66.8%,料浆质量分数为70%,灰砂比为1∶4。     

基于逐步回归分析法的炉渣-水泥-全尾砂胶结充填体强度影响分析

为降低某铜矿充填成本,探究单因素或多因素交互作用对充填体强度的影响。实验设计24组不同配比,分析了炉渣掺量、质量浓度、灰砂比耦合作用下对充填试件单轴抗压强度的影响;将炉渣掺量、质量浓度、灰砂比分别设定为解释变量X₁、X₂、X₃,单轴抗压强度设定为Y,利用软件SPSS对实验数据进行逐步回归分析,并用响应曲面法验证回归的准确性。结果表明:炉渣掺量与试件单轴抗压强度呈正相关,灰砂比越高,强度增长幅值越大;28 d强度最大增长率达138.2%;单一元素对单轴抗压强度的影响权重依次是质量浓度、灰砂比,炉渣掺量影响不显著;两种及以上影响因素交互作用下仅炉渣掺量与灰砂比交互对强度影响非常显著;两种方法回归的方程表达式基本一致,印证了回归方程的可靠性;回归拟合度达97.76%,拟合值与实验值非常接近,可将回归方程运用于该矿山充填现场。     

尾矿砂改性混凝土的强度与声发射损伤特征研究

为了研究尾矿砂改性混凝土的受压损伤特征,对4组不同磷矿尾矿砂取代率的混凝土进行了单轴压缩-声发射监测试验。根据混凝土受压损伤时所释放的声发射(AE)信号,定量探讨了材料的损伤程度,并以AE指标为基础分析了混凝土损伤演化特征。结果表明:混凝土的应力-应变曲线可分为弹性变形、塑性变形、断裂破坏和残余变形4个阶段;随着尾矿砂含量增加,混凝土的抗压强度先增加后保持稳定,尾矿砂取代率为30%(质量分数)的改性混凝土峰值抗压强度最大;由AE信号提出了损伤因子,损伤因子-应变曲线表明普通混凝土的结构损伤主要在塑性变形阶段,而尾矿砂改性混凝土的结构损伤集中在塑性变形和断裂破坏阶段;一定比例的磷矿尾矿砂有助于提高水泥砂浆的密实度,从而增强抗压强度和变形性能。这为尾矿砂改性混凝土的研究提供了重要参考。     

膏体充填材料变形性能的研究

经试验研究寻找出膏体充填材料力学参数单轴抗压强度、弹性模量、内摩擦角、内聚力与养护龄期、胶结料用量、粉煤灰用量等因素之间的影响规律以及抗压强度与弹性模量之间的关系.研究成果对不同煤矿工艺要求设计合理材料配比具有一定参考.该研究成果在河南煤化集团朱村煤矿充填项目中得以应用验证.     

Compressive properties of Napier (Pennisetum Purpureum) filled polyester composites

The effects of Napier filler on the compressive properties of an unsaturated polyester polymer were studied at various temperatures. Polyester resins with Napier filler contents of 1, 3 and 5wt-% were prepared using three different mixing methods (hand mixing, water shaker bath and hot plate stirrer). Static uniaxial compression tests were conducted to investigate the compressive stress–strain response, failure mechanisms and damage characteristics of the neat and Napier filled polyester. The results show that the elastic modulus and compressive strength of the Napier modified polyesters were improved, without significantly reducing the failure strain, by increasing the Napier content. The samples prepared by the hot plate stirrer method yielded the highest compressive strength. The strength and Young's modulus of the Napier filled polyester decreased as the temperature increased. This result suggests that the Napier filler introduced additional mechanisms of energy absorption, improving the compressive properties.     

COMPRESSION ANALYSIS OF DEHYDRATED AGRICULTURAL PRODUCTS

ABSTRACT

The textural properties of apple, banana, carrot and potato were experimentally determined by uniaxial compressive tests of cylindrical specimens at a constant deformation rate of 5mm/min. Compression tests were performed, following air drying, at various moisture contents ranging from 0.2 to 6 kg/kg db. The tests were performed using a universal texture testing machine and simple mathematical equations were used to correlate the maximum experimental stress and the corresponding strain to the moisture content. It was shown that the maximum stress decreases as the moisture content decreases, until a critical moisture content of 1.8 kg water/kg dry solids. Further removal of water tends to increase the maximum stress. The maximum experimental strain was found to increase as water was removed. The stress-strain data of compression test were modelled using a simple mathematical model, containing parameters such as the maximum stress (ow), the maximum strain (dim), the elastic parameter (E) and the viscoelastic exponent (p). The effect of the moisture content on the compressive behavior of dried materials was introduced through its effect on the model parameters. The shift in compression behavior at 1.8 kg water/kg solids leads to the conclusion that there is an important change of structure at this moisture content.     

粗骨料对混凝土单轴抗压强度及破坏特征影响的数值分析

采用PFC2D离散元首先生成混凝土基质,然后利用Clump技术形成不同形态的粗骨料混凝土数值模型,分析研究粗骨料含量和形态对混凝土强度和损伤演化的影响。获得以下主要结论：随着粗骨料含量的增加混凝土单轴抗压强度增大,相同含量下三角形粗骨料混凝土的强度最高,其次是五边形粗骨料,圆形粗骨料混凝土的强度最低;粗骨料含量小于50％时,随粗骨料含量的增大弹性模量增速较小,而大于50％时增速较大;混凝土破坏的初始微损伤主要集中在结合面处,圆形粗骨料微裂隙沿着结合面切线方向发展,主控破裂面沿着相邻粗骨料的公切线方向发展,多边形粗骨料微裂隙沿边延伸进入基质,主控破裂面为相邻粗骨料角度基本一致边的微裂隙沿边发展贯通而成。混凝土的损伤演化分为：微损伤的随机分布、微裂隙形成和微裂隙贯通形成破裂面三个阶段,粗骨料含量低时混凝土损伤比较集中,形成明显的主控破裂面,粗骨料含量高时内部损伤严重形成网状损伤裂隙。     

VISCOELASTIC BEHAVIOR OF DEHYDRATED CARROT AND POTATO

Viscoelastic properties for carrot and potato were experimentally determined by stress relaxation tests using uniaxial compressive tests of cylindrical specimens at various deformation rates (5,10 and 20 cm/min). Stress relaxation tests were performed following conventional drying at 70°C and 15% humidity for various moisture contents ranging from 10 to 80%. The tests were performed using a Zwick testing machine and the stress relaxation data were modeled using a two-term Maxwell model. It was shown that the relaxation behavior of carrot and potato was not affected by deformation rate, but it was sensitive to moisture content. The remaining force and relaxation time of the elastic component were found to be depended on moisture content. Drying tends to decrease the remaining force and the elastic relaxation time of carrot and potato until a certain moisture content (1.7 and 1.9 kg/kg db). Further uptake of water tends to increase the remaining force and the elastic relaxation time for both materials. The viscous component of Maxwell model does not seem to be affected by moisture content.     

PVC粗骨料混凝土的力学和吸能性能分析

将聚氯乙烯(PVC)软板进行粉碎得到级配良好的片状PVC颗粒以不同掺量等体积替代天然粗骨料后加入混凝土中制成试件,做单轴压缩试验和钢球自由落体冲击试验,得到立方体抗压强度、劈裂抗拉强度、卸载弹性模量和能量吸收率,用来探究不同掺量的PVC粗骨料混凝土力学和吸能性能。结果表明,随PVC粗骨料掺量增加,混凝土的抗压强度和劈裂抗拉强度均呈显著降低趋势,在实际工程中,PVC粗骨料掺量应该控制在20%左右;随PVC粗骨料掺量增加,混凝土脆性得到改善以及延性增强;混凝土的能量吸收能力随PVC粗骨料掺量增加呈显著增加趋势。     

王集磷矿尾砂特征及其充填性研究

通过对王集磷矿的尾砂特征、颗粒沉降速度、渗透系数等的测定,认为该矿充填体应处于可塑和软塑的交界线上,即稠度为7,其含水率为23.9％。折合浓度80.7％。而尾砂自然脱水时的极限含水率为31％,折合浓度76.3％。为达到尾矿充填的要求,提出了添加吸水胶凝剂、增设渗流索等降低充填料含水量的措施,并针对王集磷矿具体情况设计了可行的尾矿充填系统。     

VISCOELASTIC BEHAVIOR OF DEHYDRATED CARROT AND POTATO

Abstract

Viscoelastic properties for carrot and potato were experimentally determined by stress relaxation tests using uniaxial compressive tests of cylindrical specimens at various deformation rates (5,10 and 20 cm/min). Stress relaxation tests were performed following conventional drying at 70°C and 15% humidity for various moisture contents ranging from 10 to 80%. The tests were performed using a Zwick testing machine and the stress relaxation data were modeled using a two-term Maxwell model. It was shown that the relaxation behavior of carrot and potato was not affected by deformation rate, but it was sensitive to moisture content. The remaining force and relaxation time of the elastic component were found to be depended on moisture content. Drying tends to decrease the remaining force and the elastic relaxation time of carrot and potato until a certain moisture content (1.7 and 1.9 kg/kg db). Further uptake of water tends to increase the remaining force and the elastic relaxation time for both materials. The viscous component of Maxwell model does not seem to be affected by moisture content.