新疆某电厂CFG桩设计及施工

CFG桩是水泥粉煤灰碎石桩的简称。它是由水泥、粉煤灰、碎石、石屑或砂加水拌和形成的高粘结强度桩,和桩间土、褥垫层一起形成复合地基。CFG桩主要是针对碎石桩承载特性的一些不足,对其加以改进而发展起来的。本文拟结合新疆某电厂CFG桩的设计及施工,对CFG桩加固地基土的一些设计、施工及工后沉降等问题进行探讨。     

水泥土和CFG组合桩复合地基动力特性分析

基于优化桩型的观点,将水泥土桩和CFG桩组合成复合桩,形成刚柔组合桩复合地基,既发挥了柔性桩、刚性桩的优点又弥补了各自的不足。本文采用ANSYS有限元分析软件,对刚柔组合桩复合地基复合地基的动力特性、在地震作用下位移和加速度时程曲线进行了分析,并对刚柔组合桩复合地基抗震动力特性进行了评价,刚柔组合桩的植入较好地改善了天然地基承载和变形特性,有利于地基抗震。     

长短桩复合地基沉降数值分析

探讨ANSYS有限元分析程序在长短桩复合地基中的应用,具体分析了荷载、褥垫层、桩和土模量等因素对复合地基变形特性的影响,指出软土地区采用长短桩复合地基相对于其它复合地基能在降低工程造价的同时,有效控制沉降。     

灰土桩复合地基桩土应力比计算要点的分析

为了稳定建筑地基,就需要对建筑所在的土地进行地基处理,通过消除湿陷性提高地籍承载力。采用灰土挤密桩是一种有效的方式,本文首先分析了灰土桩复合地基桩土应力比的变化规律,然后分别从灰土桩的单桩承载力、桩间土承载力、复合地基承载力取值三个方面对复合地基承载力计算进行了分析。     

中、刚性桩复合地基的沉降、荷载与桩周土阻力探讨

从分析复合地基含桩层与非含桩层的压缩沉降入手，利用变形协调原理，建立基础变位与复合地基压缩沉降间的变形协调方程和含桩层桩顶变位与桩周土压缩之间的变形协调方程．导出了单桩承载力标准状态时基础的最大竖向沉降、复合地基的标准荷载与桩周土表面阻力，解决了复合地基目前设计理论中变形计算与受力计算相互脱节的问题，对复合地基、复合桩基的设计理论进行了大胆探讨．     

大桩距搅拌桩复合地基沉降计算方法

根据大桩距搅拌桩复合地基的变形机理,在常规复合地基加固区、软弱下卧层沉降计算方法的基础上进行了计算对比,提出复合地基加固区采用复合模量法、下卧层采用应力扩散法计算沉降的方法.阐述了大桩距复合地基沉降计算的基本假定、计算公式和具体计算步骤.结合具体的工程实例,将大桩距复合地基的计算结果与实测的沉降变形结果进行了对比分析.     

水泥搅拌桩复合地基承载力分析研究

水泥搅拌桩复合地基可以有效提高地基承载力并降低基础沉降,本文通过现场平板载荷试验研究安徽某水利工程水泥搅拌桩复合地基承载力,针对现场不合格的桩基采用换填桩帽的加固方法,并运用FLAC 3D进行了数值模拟计算,分析了换填桩帽、上层软土以及桩身强度对水泥搅拌桩复合地基承载力的影响,同时结合格栅桩复合地基承载力试验与拟合结果...     

素混凝土桩复合地基处理10万m~3储罐基础

素混凝土桩复合地基是由素混凝土桩体、桩间土和褥垫层一起构成的一种复合地基。在基础和桩顶之间设置的褥垫层是用来保证桩和土共同承担上部结构荷载。素混凝土桩复合地基具有承载力提高幅度大,地基变形小等特点,不仅可用于承载力较低的地基土,对承载力较高但变形不能满足要求的地基土,也可以采用。素混凝土桩具有较强的置换作用,在其他参数相同的情况下,桩越长,桩的荷载分担比越高。用素混凝土桩复合地基处理大型油罐基础具有明显的经济效益。     

成都地区高压旋喷桩设计中两个参数取值探讨

因成都地区地层特点,旋喷桩复合地基被广泛应用于高层建筑地基加固中。对于高压旋喷桩复合地基设计中。桩身强度和桩端阻力特征值是影响旋喷桩单桩承载力的重要因素。根据旋喷桩复合地基实践中的体会,对旋喷桩桩身强度和桩端阻力特征值两个参数取值进行讨论。通过分析,进一步认识了卵石层中旋喷桩复合地基的特殊性,并给出上述两参数取值的建议。     

水泥粉煤灰碎石桩复合地基承载性能分析

水泥粉煤灰碎石桩是复合地基施工中的常用方法,可以有效提高复合地基的承载能力。基于此,以宁夏银川市某商业住宅楼工程的水泥粉煤灰碎石桩复合地基为背景,建立了FLAC 3D数值计算模型,分析了水泥粉煤灰碎石桩和不同结构荷载对复合地基的变形破坏特征的影响规律。研究结果表明:设置水泥粉煤灰碎石桩有效降低了地基土体的最大沉降、水平位移、最大竖向应力和塑性区范围,保证上方建筑的施工和使用要求;随上方筏板基础所受荷载的增大,复合地基的地表最大沉降值、水平位移值、塑性区增大,碎石桩的竖向应力增大,复合地基的竖向应力无显著变化。     

铁质金属杂质对酚醛树脂基复合材料防热性能的影响研究

采用氧-乙炔烧蚀试验方法研究了掺杂铸钢砂杂质的酚醛树脂/高硅氧布复合材料的烧蚀性能,并利用X射线对烧蚀前的试样进行了无损检测。结果表明,X射线透射可以明显地显示铸钢砂的透射影像。复合材料的烧蚀率随着杂质粒径的减小而增加,随着杂质含量的减少而减小;掺有杂质的试样烧蚀后出现分层。     

机制砂-石屑复合细集料对不同强度等级混凝土性能的影响

为了合理利用机制砂、石屑组成的复合砂,从而缓解天然河砂的不足,通过采用级配合成计算的方法快速确定两者之间的最佳搭配比例,以获得满足国家规范II区中砂技术指标要求的复合砂。分别研究了不同掺配比例的复合砂对C30~C50强度等级混凝土工作性、力学性能及耐久性能的影响。结果表明,不同组合比例的复合砂对混凝土性能具有不同程度的改善作用,当机制砂与石屑二者的比例为6c∶4(质量比)时,各强度等级混凝土综合性能最优。     

碎屑及长江淤沙配制复合砂的试验研究

以长江淤沙和碎屑为原料,根据中砂的要求配制复合砂,并研究了其空隙率、颗粒级配、细度模数等性质。利用一定配比的复合砂成型水泥胶砂并检测了水泥胶砂的流动度、干缩率、强度等性能。试验结果表明,复合砂具有较高的密实度,复合砂配制的水泥胶砂流动性好,早期、中期、后期强度发展都优于由普通中砂配制的水泥胶砂,两者的干缩率相差不大,说明用复合砂代替天然砂来配制胶砂在技术上是可行的。     

水溶性轻质砂芯模性能与应用

以聚乙烯醇(PVAL)水溶液作为基体材料,以模型砂为增强材料,经过热烘干工艺制作了一种水溶性砂芯模材料,着重对水溶性轻质砂芯模的制备工艺特点、力学性能和水溶性能进行研究,并将所制得的水溶性轻质砂芯模成功用于树脂基复合材料结构件的制造中。结果表明,水溶性轻质砂芯模较纯砂芯模(1.60 g/cm~3)轻24%,比金属模具的钢材密度(7.85 g/cm3)轻84.5%;水溶性轻质砂芯模的压缩强度随着温度的升高而降低,当温度为150℃时,轻质砂芯模的压缩强度为4.09 MPa;水溶性轻质砂芯模的各项性能满足复合材料结构件制造的要求。     

聚氨酯复合材料磨机衬板的研究与应用

以聚氨酯、石英砂等为原料，经浇注硫化工艺复合制成聚氨酯复合材料磨机衬板，对复合材料磨机衬板的耐磨性能及其在磨机衬板上的应用进行了实验研究，并对聚氨酯与石英砂的界面结合问题进行了初步分析。     

Mechanoactivated SHS of Si–SiC Powders from Natural Sand: Influence of Milling Time

Si–SiC composite powders were SHS-produced from milled ‘natural sand–C–Mg’ precursors under pressure of Ar gas; and the effect of milling time τ on the morphology and phase composition of combustion product was investigated. The reduction in particle size of sand with increasing τ was extremely significant for the formation of Si–SiC composite powders due to an increase in the surface area of contact. Smaller sand particles yielded finer Si–SiC powders.     

Micromechanical model for compaction characteristics of bentonite–sand mixtures

This paper presents a new methodology for predicting the relationship between compaction stress and dry density, referred to herein as the compaction curve, of composite mixtures based on the micromechanics. To examine the effect of sand content on the compaction characteristics, a series of uniaxial compaction tests (UCT) for bentonite–sand mixtures with different sand fractions (by weight) were performed. In addition, a prediction model based on micromechanics for composite mixtures was developed. The developed model can be used to predict the compaction curves of composite mixtures based on experimental compaction curve of the matrix. The accuracy of the proposed model along with its applicability was examined and validated by using experimental data. The results show that the proposed model can accurately predict the compaction curves of the bentonite–sand mixtures in both loading and unloading phases.     

Studies on sand/clay unsaturated polyester composite materials

The effect of a radiation‐initiated polyester on the physicomechanical properties of a sand/clay‐polyester composite has been investigated. The unsaturated polyester resins containing various styrene contents were used at different sand/clay composites from 10 to 70 wt % with respect to the weight of sand and clay together; polymerization was conducted using γ‐irradiation at 50 kGy. Also, different particle sizes of clay (namely 1.25–0.80, 0.80–0.50, and <0.50) were used. The compressive strength, apparent porosity, and water absorption—in addition to infrared spectroscopy of the composite samples—were studied. Results indicate that the compressive strength decreases with an increase in sand/clay, as well as the styrene content in the unsaturated polyester resin, whereas the apparent porosity and water absorption of the composite samples increase. Infrared spectra showed the appearance of new bands, which indicated a chemical reaction between polyester and clay constituents. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1031–1038, 1999     

Preparation and Properties of Natural Sand Particles Reinforced Epoxy Composites

An epoxy composite using Cancun natural hydrophobic sand particle as filler material was fabricated in this study. Three point bending tests demonstrated an enhancement of 7.5 and 8.7% in flexural strength and flexural modulus, respectively, of epoxy composite containing 1 wt.‐% sand particles without any chemical treatment involved, compared to the pristine epoxy. Scanning electron microscopy (SEM) studies revealed that the fracture toughness of the epoxy matrix was enhanced owing to the presence of sand particles in an epoxy/sand composite. Through dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) methods, it was found that the storage modulus (E′), glass transition temperature (T_g) and dimensional stability of the sand particles/epoxy composites were increased compared to the pristine epoxy. The friction behavior of epoxy/sand system reflected that the microstructure of epoxy composites was steady. These experimental results suggest that Cancun sand, as a freshly found natural micron porous material, may find promising applications in composite materials.

     

复合改性生物砂滤池对突发PhACs痕量污染的去除效果分析

针对石英砂(OQS)表面特征及特性,进行表面形貌重构改性及表面涂覆改性,并根据涂覆改性差异,制备出亲水改性砂(IMS)、疏水改性砂(OMS)、阳离子改性砂(CMS)和氨基改性砂(AMS)。以实验室模拟二级处理出水为研究对象,考察以6种石英砂[4种复合改性砂、表面重构砂(对照1)及原始砂(对照2)]为核心的生物砂滤工艺对碳氮磷及突发药物活性物质(PhACs)的削减效果,分析了各组生物砂滤池微生物种群结构,并进行了生态风险评估。结果表明,各类工艺对常规污染物的去除率在24.22%～90.35%之间,CM-BSF对常规污染物的去除效果最好;6种生物砂滤工艺对5大类12种PhACs的去除率在7.9%～50.3%之间,改性砂滤工艺CM-BSF去除效果更好;高通量检测表明各组微生物物种高度相似,但丰度有差异,总体来说,具备PhACs降解能力的功能菌在复合改性石英砂覆膜生物样品中的丰度较高;通过生态风险评价方法分析,CM-BSF工艺出水产生生态风险最小。