共查询到19条相似文献，搜索用时 156 毫秒
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现多数水泥土防渗工程都间接或直接的与地下腐蚀性介质环境接触,会导致水泥土防渗性能的降低甚至失效。因此,通过室内模拟试验,设计了不同的水泥掺入比,进行了在污水和清水环境下水泥土的渗透性能试验,研究了在不同龄期下水泥土的渗透系数变化规律,并同时分析了渗透后水泥土中离子浓度的变化规律。试验结果表明,在清水环境下,随着龄期的增长,水泥土的渗透系数逐步减小,60 d后随着龄期的增加,水泥土渗透系数减小的程度越来越缓慢;在污水养护条件下,龄期在60 d之前,水泥土渗透系数逐步减小,龄期在60 d之后,由于水泥土被侵蚀,致使水泥土随着龄期的增加,水泥土的渗透系数逐步增大;无论是清水还是污水环境,随着水泥掺量的增大,其渗透系数均逐步降低;在污水环境中,随着龄期的增加,其水泥土中的Ca2+,Mg2+,Cl?, 浓度均逐步增大,而清水环境中Mg2+,Cl?, 浓度均逐步减小。其研究成果可为水泥土防渗工程的抗渗性和耐久性设计和应用提供技术参数,具有重要的工程意义。 相似文献
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填埋是污泥消化处置的方法之一,由于污泥的工程特性较特殊,填埋会引发很多环境岩土工程问题。考虑到填埋工程会进行分层碾压铺填,在标准击实试验的击实功下制备试样,通过污泥与垃圾土混合后的直接剪切试验、渗透特性试验,考虑淋滤液和降解产气压力共同影响,进行边坡稳定分析。结果表明：污泥和垃圾混合后的强度比垃圾土的强度低,比污泥的强度高,改善了污泥的强度特性;污泥掺入垃圾后的渗透系数与垃圾土的渗透系数相当,没有劣化垃圾土的渗透特性,但比污泥的渗透系数有显著提高;随着污泥掺量的增加,边坡安全系数会先提高后降低,因此,应结合试验和稳定计算结果,确定实际工程的污泥掺入比;考虑降解产气对边坡稳定的影响,安全系数会降低约15%～20%。 相似文献
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水泥稳定粉砂土抗渗性能受粉砂土自身渗透性能、水泥用量、水灰比等因素影响显著,如何在提升其抗渗性能的同时降低水泥用量是提升工程经济效益的关键。通过开展不同水泥偏高岭土掺比、初始用水量、水泥偏高岭土总掺量以及养护龄期条件下的室内渗透试验,研究了上述因素对水泥偏高岭土复合稳定粉砂土抗渗性能的影响规律,探讨了上述因素及无侧限抗压强度与渗透系数之间的经验关系。结果表明：水泥与偏高岭土掺比为5:1时,水泥偏高岭土复合稳定粉砂土抗渗性能最佳,且该掺比不随水泥偏高岭土总掺量的改变而变化;水泥偏高岭土复合稳定粉砂土渗透系数随初始用水量增加呈非线性递增,随水泥偏高岭土总掺量增加和养护龄期发展呈先快后慢降低;基于试验结果归纳提出了4个关于初始用水量、水泥偏高岭土总掺量、养护龄期和无侧限抗压强度的水泥偏高岭土复合稳定粉砂土渗透系数经验模型。研究成果可为水泥稳定粉砂土抗渗性能提升提供理论参考与借鉴。 相似文献
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水泥-膨润土泥浆配比对防渗墙渗透性能的影响 总被引：2，自引：0，他引：2
作为一种垂直防渗墙体材料,水泥-膨润土泥浆已在欧美等一些国家被广泛应用于垃圾填埋场的垂直防渗系统中,而国内对此类墙体材料的研究和应用较少。通过对不同配合比的水泥-膨润土泥浆固结体进行渗透试验,研究了原材料对泥浆固结体渗透性能的影响以及渗透性随龄期变化的情况。试验结果表明,水泥和膨润土对固结体渗透系数的影响相互依赖,只有在水泥用量达到一定程度后,增加膨润土用量才能有效地降低固结体的渗透性能;随着龄期的增加,水泥-膨润土泥浆固结体的渗透系数明显降低。 相似文献
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为探寻适用于黄土地区海绵城市建设的具有较高强度和防渗性能的路基换填材料,通过对掺入水泥、聚丙烯纤维、膨润土的黄土进行强度和渗透性试验,并基于正交试验和田口方法的信噪比分析,获得了改良黄土各掺量的最优配比方案。结果表明:水泥掺量对改良黄土的无侧限抗压强度影响最显著,聚丙烯纤维掺量和长度对其渗透系数影响最大;改良黄土各掺量的最优配比为聚丙烯纤维长度取12 mm、聚丙烯纤维掺量取0.3%、膨润土和水泥掺量分别取3%和8%;在3、7、14 d养护龄期下,最优配比改良黄土的强度和渗透性能均优于不同配比的石灰改良黄土。改良的黄土各掺量最优配比可为黄土地区海绵城市道路建设中的路基处理提供参考。 相似文献
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天然浮石粉水泥土力学性质的试验研究 总被引：2，自引：0，他引：2
利用内蒙古丰富的天然浮石矿产资源,将天然浮石粉作为外掺剂应用于水泥土改性研究,可有效地改善水泥土的力学性质,明显增强水泥土的耐久性。通过室内试验, 以水泥掺量15%为基准,分别掺入2%、4%、6%、8%、10%等不同掺量的天然浮石粉,养护龄期分别为7 d、28 d、60 d、90 d。试验结果表明：天然浮石粉水泥土无侧限抗压强度随着天然浮石粉掺量的增加而增大。当掺量达到8%时,强度达到了峰值,之后随浮石粉掺量的增加,强度不再增长;天然浮石粉水泥土强度随着龄期的增长而增大,90 d强度是28 d强度的1.52~1.6倍,后期强度增长很大;在不利的冻融循环条件下,天然浮石粉水泥土强度增长规律与冻前基本相同,水泥土强度虽然劣化,但比不掺浮石粉的情况均有很大程度的改善;浮石粉水泥土的渗透系数（对数）随着养护龄期的增长而减小,抗渗能力逐渐增强,特别是在最初的28 d以内,其渗透系数降低较快。 相似文献
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水泥粉煤灰加固有机质土的试验研究 总被引：3，自引：0，他引：3
对于高有机质含量的泻湖相软土,单纯采用水泥不能有效提高该软土的力学性能,因此提出了采用水泥和粉煤灰作为固化剂的加固方法。通过不同水泥掺入量、粉煤灰掺入量和龄期下水泥土的无侧限抗压强度试验,分析了水泥粉煤灰固化土的强度规律和变形规律,探讨了水泥和粉煤灰加固高有机质含量软土的机理。结果表明,粉煤灰对于水泥试块的早期强度影响较小,对后期强度影响较大;粉煤灰最佳掺入量为12％,超过此掺入量水泥土强度反而会降低,粉煤灰水泥土的破坏应变、E50也在粉煤灰掺量为12％时分别达到最低值和最大值。水泥掺加粉煤灰可有效地提高高有机质含量软土的强度。 相似文献
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以不同水泥掺量的水泥黏土为研究对象,进行核磁共振试验研究水泥掺量对微观孔隙分布的影响,进行变水头渗透试验研究水泥掺量对渗透性的影响,在此基础上调查水泥掺量对渗透性影响的微观机制。研究发现:水泥土的渗透系数随水泥掺量的增大而减小,其中在低水泥掺量（4%~12%）范围内急剧减小,在高水泥掺量（15%~25%）范围内呈现相对缓慢减小趋势;水泥土T2分布曲线均呈现三峰分布,三峰分别对应于小孔、中孔、大孔,随着水泥掺量增加,T2分布曲线总面积呈现减小趋势,其中在低水泥掺量范围内,第2峰、第3峰峰面积减小明显,在高水泥掺量范围内,第1峰峰面积显著减小。分析可知,在水泥掺量较低时,水泥水化作用优先堵塞大孔和中孔,导致渗透系数随水泥掺量增加而显著减小;在水泥掺量较高时,水泥掺量的增加主要减少小孔隙面积,大孔和中孔面积变化不大,此时增加水泥掺量对减小水泥土渗透系数的效果相对较差。 相似文献
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I. N. Markou D. N. Christodoulou E. S. Petala D. K. Atmatzidis 《Geotechnical and Geological Engineering》2018,36(2):959-981
One-dimensional injection tests were conducted on dry and dense sand columns with a height of 36.5 cm for the injectability evaluation of cement grouts. Three ordinary cement types were pulverized to obtain fine-grained cements having nominal maximum grain sizes of 40, 20 and 10 μm. Suspensions of these cements with water to cement (W/C) ratios of 1, 2 and 3, by weight, were injected into 54 clean, limestone sands with different gradations. Pulverization of the ordinary cements to produce microfine cements extends the range of groutable sands to “medium-to-fine”. Suspension injectability is improved by increasing cement fineness and suspension W/C ratio or by decreasing apparent viscosity and is controlled by the synthesis of the finer portion (d ≤ d25) of the sand gradation. The outcome of the 131 injectability tests conducted is successfully predicted by available groutability criteria at a rate ranging between 51 and 69%. The “new groutability and filtration criteria” proposed in this study, are adapted to the finer 25% of the sand gradation, have successful predictions for 79% of the cases (10–28% higher than those of the existing groutability criteria) and predict successfully the appearance of filtration in 83% of the available cases. The model developed by performing Binary Logistic Regression analyses of the injection test results is considered appropriate for the prediction of injectability of cement grouts in sands because it exhibits a coefficient of multiple determination equal to 0.84 and provides a rate of successful predictions equal to 78% of the available experimental results. 相似文献
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An experimental investigation was conducted in order to evaluate the influence of distance from the injection point and of parameters pertinent to the cement, the suspension and the sand on the effectiveness of microfine cement grouts. Three different cement types, each at three different gradations having nominal maximum grain sizes of 100, 20 and 10 μm, were used. Grouting effectiveness was evaluated by injecting suspensions with water to cement (W/C) ratios of 1, 2 and 3, by weight, into five uniform sand fractions with different grain sizes and eight composite sands with different gradations, using a specially constructed apparatus. Unconfined compression and permeability tests were conducted on the resulting grouted sand specimens, after curing for 28 and 90 days. Microfine cement grouted sands obtained unconfined compression strength values of up to 14.9 MPa and permeability coefficients as low as 1.3 × 10?6 cm/s or by up to 5 orders of magnitude lower than those of clean sands. The W/C ratio and the bleed capacity of suspensions as well as the effective grain size and the permeability coefficient of sands are very important parameters, since they affect substantially the grouted sand properties and are correlated satisfactorily with them. The strength and permeability of grouted sands can increase, decrease or remain constant with distance from the injection point depending on the easiness of suspension penetration into the sands. The improvement of grouted sand properties with increasing distance from the injection point is consistent with the observed increase of the cement content of grouted sands. 相似文献
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在以干密度控制配比的原则下,对砂土与EPS颗粒混合轻质土（LSES）和其原料土砂土进行了动力变形特性对比试验研究。试验表明,LSES与纯砂的动弹性模量具有同样的随应变的增大而减小的性质,不同EPS颗粒体积含量和水泥掺入比的LSES动弹性模量普遍高于纯砂的动弹性模量。LSES与纯砂均显示出动弹性模量随围压的增大而增大的特性,围压对LSES的动弹性模量影响与纯砂相比相对较大。LSES与纯砂的等效阻尼比在整体上具有同样的随应变的增大而增大的性质。水泥掺入比较小时,LSES的等效阻尼比与纯砂相近;在高水泥掺入比下,不同EPS颗粒体积含量的LSES等效阻尼比均低于纯砂的等效阻尼比。LSES与纯砂均显示出等效阻尼比随围压的增大而减小的特性。围压对纯砂与LSES等效阻尼比的影响程度相近。 相似文献
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华南海岸沙丘岩的特征及其形成发育模式 总被引：10，自引：0，他引：10
海岸沙丘岩是一种热带、亚热带干旱及季节性湿润地区特有的碳酸盐胶结的风成碎屑岩。本文对华南沿海沙丘岩的沉积结构、沉积构造特征,地球化学与古生物特征,及其胶结类型、成岩机制和发育模式进行了较系统研究,并讨论了与海滩岩的区别。 相似文献
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综合利用岩心、岩石薄片、扫描电镜及测井等资料,对准噶尔盆地莫索湾—莫北地区侏罗系八道湾组致密油储层特征及其致密化成因进行研究。结果表明:八道湾组储层为低—特低孔、低—特低渗储层,属典型的深层致密砂岩储层;储层砂体主要为三角洲前缘水下分流河道细砂岩、中—细砂岩,成分成熟度低,具有岩屑和塑性岩屑含量高及胶结物含量低的"两高一低"特征;垂向上以4 100和4 500m为界,可划分为减小原生孔、稳定混合孔及增加次生孔3个孔隙演化带;孔隙主要为中—小孔,孔喉类型以分选较差的中-细孔—细喉型为主,连通性和渗流能力相对较差,结构相对较差。储层致密化主要受控于沉积环境相对稳定性、岩石主要成分、储层埋藏深度及胶结物赋存状态4个因素,构成了致密化的背景、内因和外因;相对稳定的沉积环境、低成分成熟度、高岩屑和塑性岩屑含量、储层埋深大、压溶作用大量减孔,以及不同类型胶结物以4种状态充填孔喉,形成了八道湾组致密储层。 相似文献
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In this paper, an experimental investigation of cement treated sand is performed under triaxial tests in order to quantify
the effects of cementation on the stress–strain behavior, stiffness and shear strength. Samples were cured up to 180 days.
The results show that the stress–strain behavior of cemented sands is nonlinear with contractive–dilative stages. The stress–strain
response is strongly influenced by effective confining pressure and cement content. Stiffness and strength are greatly improved
by an increase in binder content. An increase of the angle of shearing resistance and cohesion intercept with increasing cement
content is observed consistently. Brittle behavior is observed at low confining pressure and high cement content. After yielding,
the increase in the dilatancy accelerates. Two competing related processes determine the peak strength: Bond breakages cause
a strength reduction but the associated dilatancy leads to a strength increase. This finding and the experimental observation
that the dilatancy at the peak state increases with increasing cement content explain why the measured peak-state strength
parameters, c′ and φp′, are relevant to the binder content. 相似文献
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Zhang Fengshou Wang Tuo Liu Fang Peng Ming Bate Bate Wang Pei 《Acta Geotechnica》2022,17(8):3535-3551
Oil or gas production from unconsolidated reservoirs could be hampered by sand migration near the wellbore. This paper presents a numerical investigation of production-induced migration of fine sands towards a wellbore drilled in a gap-graded sediment. The solid–fluid interaction is simulated by coupling the discrete element method and the dynamic fluid mesh. With the merit of DEM and a dynamic mesh, the model is capable of naturally capturing particle movements and spatiotemporal variations of hydraulic properties of the sediment at the pore scale. The results show that fine particles are mobilized by radial flow under an imposed hydraulic gradient, and the increase in the hydraulic gradient causes an increase in the fines production. The microscopic pattern of sand migration is clearly visualized through the simulation. The presence of fine particles affects the process of fines migration through two competing mechanisms. Under a low fine content, fine sands mainly serve as the fines production source, and thus, fines production is enhanced as the fine content increases up to a critical value, beyond which fines production is weakened with a further increase in the fine content since the blocking effect gradually dominates. A barrier layer is likely formed during sand migration due to settling and jamming of fine sands at the throats of pores, as fine sands migrate with the radial flow towards the wellbore. This layer is helpful to slow down sand migration, while it could impede production due to reduced permeability in the affected reservoir.
相似文献