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Yuqing YUAN Xuancang WANG Xin ZHOU 《Frontiers of Architecture and Civil Engineering in China》2008,2(4):359-365
Unlike other road materials, aeolian sand has some compaction characteristics that are key factors in construction qualities
of highway in the desert. In order to study the characteristics, a series of laboratory and field tests were performed, including
sieve analysis, standard modified compaction, vibrating compaction and field test. By analyzing the sieve analysis test data,
it was found that the gradation of aeolian sand was bad, with fine grains whose diameters mostly ranged from 0.25 mm to 0.074
mm. Then, from the laboratory compaction test results, a compaction curve similar to the horizontallywritten letter S was
obtained. That was quite different from the other kinds of road materials. There were two peak values in the curve with the
increase of water content, which was the special characteristic of aeolian sand: to be well compacted whether it was dry or
wet. Also, according to laboratory vibrating test results, the best vibrating frequency range was proposed. It was from 45
Hz to 50 Hz. Moreover, some field compaction tests were carried out. On the construction site of the highway, the aeolian
sand subgrade was compacted in the condition of natural water content with optimizing construction machines. Its compaction
degree reached 96%, meeting the current specifications. At last, comparative studies were carried through with electron microscope.
It was shown that the microstructure of compacted dry aeolian sand is much denser than that of the natural one in the field
test.
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Translated from Chinese Journal of Geotechnical Engineering, 2007, 29(3): 360–365 [译自: 岩土工程学报] 相似文献
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风积沙是一种特殊的筑路材料,其压实特性是影响沙漠公路施工质量的重要因素。为了研究风积沙的压实特性,进行了筛分试验、标准重型击实试验和振动试验及野外现场试验。筛分试验结果表明:风积沙级配不良,沙粒均匀,粒径主要分布在0.25~0.074 mm之间,属于细砂;击实曲线与常规工程材料显著不同,呈一个特殊的横写S型,干密度随含水率变化有两个峰值,揭示了风积沙在含水率为0和最佳含水率下,均可以达到最佳密实度的特有性质。振动试验表明:风积沙的最佳振动频率为45~50 Hz。现场试验进行机械优化配置,采用干压实工艺,试验压实度代表值达到了96%,效果良好。沙样的电镜扫描图显示,振动干压实后,风积沙微观结构良好,达到了预期的效果。 相似文献
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长江口细砂作为路基填料的工程特性研究 总被引:2,自引:0,他引:2
选择了有代表性的5种长江口细砂进行级配、压实特征、湿度特征、回弹模量的室内和现场试验.结果表明:长江口细砂粒径较为单一,多在0.075~0.300mm之间,不均匀系数小于5;采用小型试筒重型击实试验可减小击实对周边压实砂粒的扰动,且最大干密度测试结果高于大型试筒;击实曲线呈现多峰特征,含泥量越低,驼峰数越多,对现场施工压实控制更为有利;低填细砂路基在运营过程中受地下水影响较小,CBR强度和回弹模量与压实度、含泥量相关性显著,能满足设计要求,且经100万次加载后无显著衰减. 相似文献
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压实风积沙土层盐分迁移规律研究 总被引:1,自引:0,他引:1
针对沙漠地区风积沙路基发生盐渍化病害现象,探究压实风积沙土层水、热、盐变化规律。自制下垫面为硫酸钠盐渍土地基的风积沙土柱试验设备,以自然环境条件下6个月(6月—12月)的实时监测数据为基础,分析压实风积沙土层内水、热、盐的时空分布规律与迁移特征。研究结果表明:受外界环境温度影响,压实风积沙土层分影响剧烈区(0~50cm)与薄弱区(50~120cm),随着埋深增加,土柱内部温度变化幅度趋于平缓,各层温度到达峰值具有滞后效应;受含盐下垫面与压实素土风积沙含盐量的浓度梯度作用,压实风积沙土层深部区域被盐分迁入,由无到有。风积沙土层内盐分的存在,为盐分的进一步迁移奠定了物源基础。由外界温度影响,土层浅部受水分赋存形态的变化与蒸发牵引作用,促使水分携带盐分在压实风积沙土层内部逐渐向上发生迁移;盐分在土层整个埋深断面上呈现"高—低—高"的分布特征。受外界环境荷载周而复始作用,压实风积沙土层浅部盐分将渐渐积聚,由少到多,随着时间推移将形成盐渍化病害。 相似文献
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主要介绍了风积沙路基不同设计形式在高等级公路中的应用,并总结出干压和湿压两种不同的施工工艺,同时提出了进一步进行风积沙路基设计的建议。 相似文献
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沙漠地区高速公路路基风积沙填筑施工技术 总被引:1,自引:1,他引:0
通过对沙漠地区高速公路路基风积沙填筑施工过程的阐述,详细介绍了风积沙填筑的特殊施工技术,实践证明风积沙作路基填料是可行的,指出风积沙路基施工中必须采取特殊的施工工艺和压实方法来确保风积沙路基的工程质量。 相似文献
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击实对固化淤泥物理力学性质的影响 总被引:2,自引:0,他引:2
淤泥固化技术中国进行工程应用时经常遇到需要碾压施工的问题,碾压后固化淤泥的力学性质是亟需试验明确的问题。研究了击实对不同水泥添加量和不同养护龄期下固化淤泥的密度、干密度、CBR和无侧限抗压强度的影响规律。结果表明,击实过程中存在有效击实次数,超过此次数后不能使土体进一步密实,击实土能达到的密度、干密度基本与固化土的相等;击实土的CBR强度可以从固化土的CBR得到,且约为固化土的1/10,固化土的CBR性质能够满足作为路堤填土的要求,而击实土则不能;固化土的抗压强度越大,击实土的抗压强度也越高,但是击实土相对于固化土的强度损失也就越大,击实土的无侧限抗压强度为固化土的1/3~1/2。因此,应根据实际淤泥固化工程的特点,合理选择水泥、石灰或复合型固化材料,这方面研究还有待更深入地开展。 相似文献
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《Construction and Building Materials》2010,24(9):1790-1795
Compacted sand concrete is being researched for potential usage in road construction because of shortage in gravel resources in many countries. However, one of the problems for this material with such application is shrinkage cracking. This paper presents the results of the unrestrained shrinkage test performed on three different compacted sand concrete mixes. Two existing shrinkage prediction models, namely the ACI 209 and the CEB 90, were used to fit the measured shrinkage data. The CEB 90 model with an application of a correction factor was found to perform well with compacted sand concrete. Based on the results of the shrinkage tests, joint spacing between compacted sand concrete slabs was calculated. 相似文献
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皖北地区稳定粉砂土由于土质中的细粒较多,不可直接用作公路路基的基层填筑材料。为此,要研究该地区稳定粉砂土的压实特性,分析影响压实的因素和压实规律,并提出适宜此类土的压实工艺、施工控制指标,并将其运用在各等级公路施工中。 相似文献
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大西铁路客运专线上白隧道穿越干燥粉细砂地层,施工难度及风险很大。通过现场密排小导管和深层咬合桩预加固效果对比试验,得出深层咬合桩预加固可有效控制开挖中的流砂及涌砂。同时,对粉细砂地层及深层咬合桩固结体进行直剪试验、三轴试验及侧限压缩试验等室内试验,得到地层及固结体的各项物理力学指标,且认为三轴试验所得各指标更为真实、可靠。在此基础上,对干燥粉细砂地层隧道开挖方法进行数值模拟和现场试验测试,提出合理的施工方法建议。研究结果为上白隧道施工提供技术支持,也可供类似工程参考。 相似文献
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《Soils and Foundations》2014,54(4):731-747
In recent years, earthquakes and heavy rains have frequently caused soil embankments to collapse. In order to prevent the collapse of embankments, it is well known that sufficient compaction and drainage control are necessary. Although numerous research findings have described compacted soils, compaction management has been essentially based on simple parameters such as dry density, degree of saturation or air content. It is important for the construction of a stiff embankment that the effect of compaction condition on the mechanical properties and inherent anisotropy of compacted soil should be recognized in detail. In the present study, the relationships between the compaction condition and the mechanical properties obtained from laboratory tests using saturated specimens are presented. Specifically, undrained monotonic and cyclic shear strength, shear modulus, and permeability are reported. The arrangements of soil particles were also observed with a microscope. From the observation of fabric characteristics of soil particles, an inherent anisotropy of compacted soil is discussed. Furthermore, a conceptualization of the relationship between the fabric of soil particles and the mechanical characteristics for each compaction condition is suggested. 相似文献
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对风积沙最大干密度的确定及施工机械的要求与选择进行了介绍,阐述了沙路基填方的施工要求,论述了风积沙路基的压实工艺,并对风积沙路基石灰土封层的施工进行了介绍,以供类似工程参考。 相似文献
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全风化泥质砂岩强度低,遇水后易崩解、软化,表现出与一般填料不同的工程特性。采用X射线衍射试验分析土样矿物成分,采用压缩试验和平板荷载试验研究重复加卸载条件下土样累积变形与湿化规律,以指导现场压实控制。结果表明:(1) 全风化泥质砂岩填土的压缩曲线在固结仪中呈下凹型,在平板荷载试验中呈上凸型,回弹曲线均呈下凹型;(2) 第i+1次压缩–回弹曲线均位于第i次曲线下方,线形相似;(3) 等载压缩次数增加,沉降增量递减,累积沉降增大,3次压实后,土体的残余变形趋于稳定;(4) 超载压缩曲线将回归到首次压缩曲线的延长线上,具有记忆效应;(5) 重复荷载越大,单次压缩总变形和永久变形越大;(6) 重复荷载作用后的压实填土遇水产生湿化沉降;(7) 湿化土的压缩–回弹曲线均呈下凹型,超载越高,相同荷载作用下的变形越小。现场压实过程中,增加压路机能量比增加压实次数可取得更好的压实效果。 相似文献
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针对砂性土路堤施工中经常遇到的路基压实度检测结果出现压实度超100%的“超百”现象,从填筑材料材质的不均匀性方面进行原因分析。针对填科舍石率的差异,提出通过不同舍石率的标准击实,得出不同含石率下的标准击实曲线,对照标准试验与施工现场填料材质的一致性,从而正确处理超100%的“超百”现象。此法经过工程实践取得良好效果。 相似文献