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1.
岩土体热导率是热物理性质重要参数之一,不仅仅决定着浅层地温场的展布形态,而且也是整个热泵功率计算的核心,是影响地源热泵工程投资和运行能耗的关键因素.本文通过一系列实验,对粉质粘土的热导率与含水量、密度、孔隙比进行研究和统计,从实验研究结果来看,粉质粘土热导率随着含水量的增大而增大,可以用对数关系和乘幂关系进行拟合,相关系数较好,由于样品物质成分和微观结构差异影响着传热方式组合,难以用统一的拟合方程表示同一地区热导率与含水量等因素变化规律.在含水率不变的情况下随着孔隙比的增大而热导率逐渐减小,随密度的增加而热导率增大的规律趋势明显.粉质粘土热导率随含水量的变化可分为3个阶段,含水量在0～5％,热导率随之增加急剧,含水量5％～20％时,热导率随之增加较快,含水量大于20％时,热导率随之增加缓慢并趋于稳定. 相似文献
2.
土体内在结构对热导率计算模型的影响研究 总被引：2，自引：1，他引：1
为得到适用于土体的热导率模型,利用软件将土样扫描电镜图片（反映土体的真实结构）二值化,采用瞬态传热分析方法对土体进行二维传热分析,通过ANSYS模拟土体并分析得出土体热导率。并且将数值分析结果与实测结果进行对比,发现两者间误差较小,说明该方法能较精确地得到土体热导率,为土体热导率理论模型的建立提供了一种新方法。在此基础上,对粉砂、粉土及粉质粘土的热导率进行研究,发现土体热导率随孔隙率的增大而减小,粉砂热导率的减小速率最大,其次为粉土,最小为粉质粘土。 相似文献
3.
影响北京地区粉质粘土和细砂的热导率因素统计分析 总被引：1，自引：1，他引：0
随着能源短缺和人们环保意识不断提高,浅层地下空间的有限资源得到了快速开发利用,为高效合理使用地下有限热能,有必要研究岩土体的热物理参数变化规律。在北京平原区浅层地温能资源地质勘查项目岩土体热物理性质测试和土工试验的基础上,对粉质粘土和细砂的热导率影响因素进行数理统计分析。从统计结果来看,在天然含水率条件下,粉砂质粘土的平均热导率为1.74 W/(m.K),细砂的平均热导率为1.55 W/(m.K),两者的热导率均随天然含水率、天然密度、孔隙比的变化趋势明显:随着含水量的增大而热导率逐渐减小,随密度的增加而热导率增大,随着孔隙度的增加则热导率逐渐降低,粉质粘土含水量在20%左右热导率最佳,细砂含水量在15%左右热导率最佳;由于样品物质成分和微观结构差异影响传热方式组合,因而导致不同地区乃至相同地区热导率与含水量等因素拟合方程形式不尽相同,但变化规律趋势相似。 相似文献
4.
广西红粘土击实样强度特性与胀缩性能 总被引：15，自引：0，他引：15
通过对广西贵港红粘土重型击实样的室内试验研究,探讨了其力学特性、胀缩性能、孔径分布特征与含水量之间的关系。结果表明：干密度指标总体上能反映红粘土击实样的强度规律,但非饱和击实样强度峰值对应的含水量因基质吸力作用而偏小,饱和后土体由于吸水膨胀与基质吸力的消失,使得强度峰值对应含水量较饱和前明显增大,红粘土在最优含水量下压实,虽可获得很高的压实度,但饱和后的强度并非最大;红粘土击实样的胀缩性能主要由含水量决定,同时,受到干密度的影响;孔隙主要以孔径在0.01～0.05μm范围内的小孔隙为主,为进一步掌握红粘土的工程力学特性提供了帮助。 相似文献
5.
针对胶济客运专线非饱和原状粉质粘土,在控制基质吸力条件下进行了K0固结试验和常基质吸力固结试验研究,得到了不同含水量土体的侧压力系数,并在此基础上进行常基质吸力固结试验,通过分级施加围压和上覆应力对现场应力状态进行模拟,得到原状粉质粘土的水土特征曲线,进而探讨了非饱和粉质粘土的水土特性及体变规律。试验结果表明:不同含水量的非饱和土体侧压力系数不同,并且侧压力系数随含水量的增加而增加;非饱和原状粉质粘土的进气值约25kPa;土体饱和度对固结时间的影响显著,非饱和粉质粘土的固结速度随着饱和度的增加而减小。 相似文献
6.
针对深厚表土层对煤炭资源开采可能带来的安全生产及地表环境破坏问题,利用分形理论方法研究了鲁西南地区大埋深粘土的微孔隙发育规律。研究表明,该区深部粘土孔隙累计分布与孔径大小之间在双对数坐标下具良好的线性关系,相关系数在0.90以上。说明深部粘土中孔隙分布的分形结构是客观存在的,而分维值能真实地反映粘土孔隙特征,可作为一个综合指标,它也是土体孔隙定量描述的有效途径。这种粘土的孔径大于1μm左右时,其分维值在2.5~2.6。同时得出︰孔隙孔径2μm左右是该区深部粘土孔隙性质变化的界限。 相似文献
7.
滇西北小中甸盆地是上新世末期以来在青藏高原强烈隆起过程中形成的NNW向第四纪断陷湖盆地,从深切的小中甸河谷剖面可见盆地上部发育中晚更新世湖相粘土。规划建设中的滇藏铁路将从小中甸盆地穿过。野外调查发现小中甸湖相粘土厚数十米以上,粘土细腻、层理发育。室内试验表明:小中甸湖相粘土是一种高分散性、高含水量、高塑性和高孔隙性的结构性粘土,其力学性质指标表现为高粘聚性、以中低膨胀性为主。工程开挖卸荷、浅表层土体暴露在干湿交替环境中,土体收缩强度衰减,由此产生土体差异变形和粘土边坡滑塌破坏。 相似文献
8.
滇西北小中甸盆地是上新世末期以来在青藏高原强烈隆起过程中形成的NNW向第四纪断陷湖盆地,从深切的小中甸河谷剖面可见盆地上部发育中晚更新世湖相粘土.规划建设中的滇藏铁路将从小中甸盆地穿过.野外调查发现小中甸湖相粘土厚数十米以上,粘土细腻、层理发育.室内试验表明:小中甸湖相粘土是一种高分散性、高含水量、高塑性和高孔隙性的结构性粘土,其力学性质指标表现为高粘聚性、以中低膨胀性为主.工程开挖卸荷、浅表层土体暴露在干湿交替环境中,土体收缩强度衰减,由此产生土体差异变形和粘土边坡滑塌破坏. 相似文献
9.
广西原状红粘土力学性状与水敏性特征 总被引：19，自引：6，他引：13
对广西原状红粘土的力学指标、胀缩特性与孔径分布随脱湿过程的演化规律进行了较为系统的室内试验研究。结果表明：广西原状红粘土为裂隙发育的硬塑性粘土,不同脱湿阶段的力学指标与胀缩性能在较高含水量范围内受基质吸力控制,在较低的含水量范围内主要受控于裂隙性;转折点处含水量与重型击实(干法备样)最优含水量相接近;原状红粘土的孔隙主要以孔径从0.01 μm～0.05 μm的小孔隙为主,在脱湿过程中,干密度增大,总孔隙体积减小,以0.01 μm～0.05 μm与0.1 μm～1.0 μm两个区间内孔隙体积减小最为明显。 相似文献
10.
上海软粘土微观特性及在土体变形与地面沉降中的作用研究 总被引：18，自引：3，他引：18
对上海软粘土的颗粒及集合体成分、孔径分布、微结构、孔隙溶液与阳离子交换性作了分析 ,对固结前后的孔径变化与人工回灌对土体性质可能带来的影响作了探讨 ,从物理化学角度阐述了软粘土微观特性对土体固结变形及地面沉降的影响. 相似文献
11.
青藏高原含砂砾石土壤导热率实验研究 总被引：4，自引：1，他引：3
土壤导热率是土壤的基本物理参数之一,也是陆面模式的重要输入量,对研究土壤热传输、水热耦合运移有重要意义。青藏高原由于独特的地理环境备受学者关注,但目前常用的土壤水、热属性参数化方案仅仅考虑了沙土、粉土和黏土,就砂砾石重要性的认识还不足,很少有模式模拟砾石对青藏高原多年冻土和高寒草地的影响。采用便携式热导仪（KD2 Pro,DECAGON,美国）测量了青藏高原玛多和北麓河两地典型土壤在冻结和未冻结状态下不同水分条件时的土壤导热率,分析了砂砾石含量对土壤孔隙度的影响及冻结和未冻结状态下,不同水分条件下砂砾石含量对土壤导热率的影响。结果表明：当含水量高于某一阈值时,含水土壤冻结状态下的导热率高于未冻结状态下的导热率;土壤含水量对土壤导热率影响显著,导热率随着含水量的增加而增大,在含水量较小时变化更明显;砂砾石含量比重多的土壤孔隙度较小,且砂砾石含量越大的土壤在冻结状态下导热率高。以上结果表明,砂砾石对土壤导热率有显著影响,在将来的模式模拟研究中必须考虑砂砾石对土壤热属性的影响,进而提高土壤水热过程模拟的精度。 相似文献
12.
热性质是岩土体基本的物理性质之一,用以评价热量在其中的保持、传导和分布状况,以导热系数、比热容和热扩散系数最为常见,这些参数也是地热能管理与开发、工程冷冻开挖、寒区工程设计与施工的重要参数。已有研究表明,土壤热参数与土质、来源、含水率、密度等因素有关。通过广东湛江某工地粉质黏土和黏土的热参数测试结果分析发现：随含水率的增大,粉质黏土导热系数和热扩散系数的变化趋势是先增加至最大值,然后减小,而比热容基本呈线性增大。干密度对粉质黏土导热系数的影响与含水率大小有关,当含水率不超过20.0%时,其随干密度的增加而增大,而当含水率超过27.5%后,其随干密度的增加有减小趋势;当含水率在24.5%（液限）左右时,基本没有规律可循。干密度对粉质黏土热扩散系数影响规律不明显。黏土的导热系数和比热容都随含水率和干密度的增加而增大;热扩散系数随含水率的升高整体表现为非线性增加至稳定,在低含水率下干密度的影响不明显,在较高含水率下随干密度的增加热扩散系数先增大后减小。较大颗粒的存在导致粉质黏土的导热性较黏土复杂。 相似文献
13.
Influence of soil moisture content on surface albedo and soil thermal parameters at a tropical station 总被引：1，自引：0，他引：1
Half hourly data of soil moisture content, soil temperature, solar irradiance, and reflectance are measured during April 2010 to March 2011 at a tropical station, viz., Astronomical Observatory, Thiruvananthapuram, Kerala, India (76°59’E longitude and 8°29’N latitude). The monthly, seasonal and seasonal mean diurnal variation of soil moisture content is analyzed in detail and is correlated with the rainfall measured at the same site during the period of study. The large variability in the soil moisture content is attributed to the rainfall during all the seasons and also to the evaporation/movement of water to deeper layers. The relationship of surface albedo on soil moisture content on different time scales are studied and the influence of solar elevation angle and cloud cover are also investigated. Surface albedo is found to fall exponentially with increase in soil moisture content. Soil thermal diffusivity and soil thermal conductivity are also estimated from the subsoil temperature profile. Log normal dependence of thermal diffusivity and power law dependence of thermal conductivity on soil moisture content are confirmed. 相似文献
14.
为了探讨非饱和含砂细粒土的气体渗透规律,制备不同含水率和干密度试样进行气体渗透试验,并基于多孔介质渗流理论分析进气压力、孔隙比和饱和度等对气体渗透率的影响规律,总结了非饱和土中渗透率的经验公式。试验结果表明,随着进气压力的增加,土样气体渗透率测试值逐渐趋于稳定值;含水率较高时,进气压力对土样气体渗透率的影响程度较大;含水率较低时,土样气体渗透率随进气压力增加而变化幅值较小。气体渗透率随土样含水率的增加（或饱和度的增加）呈减小趋势;当含水率低于最优含水率时,气体渗透率变化较小,但当含水率大于最优含水率后,气体渗透率急剧降低;在最优含水率两侧,土样微观结构的差异（絮凝结构和分散结构）是导致气体渗透率发生突变的主要原因;气隙比可有效表征土体孔隙比与饱和度对气体渗透率的影响规律,气体渗透率与气隙比呈良好的幂函数关系,并采用已有文献中试验数据验证了经验公式的合理性。 相似文献
15.
Study on the influencing factors of rock-soil thermophysical parameters in shallow geothermal energy 
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下载免费PDF全文 Thermophysical parameters are the main parameters affecting the utilization efficiency of shallow geothermal energy. Based on the research and evaluation data of shallow geothermal energy in capital cities of China, this paper analyzes the differences between two testing methods and finds that data measured in in-situ thermal conductivity test is closer to the actual utilization. This paper analyzes the influencing factors of thermophysical parameters from lithology, density, moisture content and porosity: The thermal conductivity coefficient of bedrock is generally higher than Quaternary system loose bed soil; as for the coefficient of bedrock, dolomite, shale and granite are higher while gabbro, sandstone and mudstone are lower; as for the coefficient of loose bed, pebble and gravel are higher while clay and silt are lower. As the particle size of sand decreases, the thermal conductivity coefficient declines accordingly. The thermal conductivity coefficient increases linearly with growing density and decreases in logarithm with growing moisture content as well as porosity; specific heat capacity decreases in logarithm with growing density, increases in power exponent with growing moisture content and decreases linearly with growing porosity. The thermal conductivity coefficient is high when hydrodynamic condition is good and vice versa. The conclusions of this paper have guiding significance for the research, evaluation and development of shallow geothermal energy in other areas. 相似文献
16.
Investigating soil thermodynamic parameters of the active layer on the northern Qinghai-Tibetan Plateau 总被引：3，自引：1，他引：2
Ren Li Lin Zhao Tonghua Wu Yongjian Ding Yao Xiao Yongliang Jiao Yanhui Qin Yufei Xin Erji Du Guangyue Liu 《Environmental Earth Sciences》2014,71(2):709-722
The soil thermodynamic parameters, including thermal conductivity, diffusivity and volumetric capacity within the active layer on the northern Tibetan Plateau, were calculated using the measured data of soil temperature gradient, heat flux, and moisture at four stations from October 2003 to September 2004. The results showed that the soil thermodynamic parameters exhibited clear seasonal fluctuation. The thermal conductivity and diffusivity in summer and autumn at Beiluhe, Kexinling, and Tongtianhe were larger than those in winter. The volumetric thermal capacity causes an opposite change; it was larger in autumn and winter than in summer. In spring, the soil thermal conductivity at the Kekexili station was larger than that in summer. Generally, fine-grained soils and lower saturation degrees in the topsoil might be a reason for the lower soil thermal conductivity in winter. For a given soil, soil moisture was the main factor influencing the thermodynamic parameters. The unfrozen water content that existed in frozen soils greatly affected the soil thermal conductivity, whose contribution rate was estimated to be 55 %. The thermodynamic parameters of frozen soils could be expressed as a function of soil temperature, volumetric ice content and soil salinity, while for the unfrozen ground the soil moisture content is the dominant factor for those thermal parameters. As for the soil thermal diffusivity, there exists a critical value of soil moisture content. When the soil moisture content becomes less than a critical value, the soil thermal diffusivity increases as the soil moisture content rises. 相似文献
17.
目前国际上对高温下土壤热导率的试验和模型预测研究比较缺乏,通过KD2 Pro测试两种红黏土在较广温度范围（5~90℃）和含水率范围内的热导率,并选择IPCHT模型预测高温下体积含水率-热导率的变化规律。测试结果表明,两种红黏土的热导率对体积含水率的敏感程度与温度有关,且热导率均随温度的升高而增大,在90℃时热导率最高可达5℃的3~4倍。60~90℃范围内热导率随体积含水率的变化存在明显的临界含水率（对应土壤的塑性指数）,但相同温度、体积含水率下,柳州红黏土中水汽潜热传输效应较桂林红黏土要明显。模型预测研究表明,除粉砂质黏壤土外,高温下IPCHT模型预测效果均不理想,经传质增强因子ξ修正后,柳州红黏土以及细砂的热导率预测值和实测值均相符得较好（RMSE < 30%）,但桂林红黏土的整体预测效果仍较差。 相似文献
18.
As the demand of exploitation and utilization of geothermal energy increases, more geothermal-related earth structures occur recently. The design of the structures depends upon an accurate prediction of soil thermal conductivity. The existing soil thermal conductivity models were mostly developed by empirical fits to datasets of soil thermal conductivity measurements. Due to the gaps in measured thermal conductivities between any two tested natural soils, the models may not provide accurate prediction for other soils, and the predicted thermal conductivity might not be continuous over the entire range of soil type. In this research, a generalized soil thermal conductivity model was proposed based on a series of laboratory experiments on sand, kaolin clay and sand–kaolin clay mixtures using a newly designed thermo-time domain reflectometry probe. The model was then validated with respect to k dry–n (thermal conductivity of dry soils and porosity) and k r–S r (normalized thermal conductivity and degree of saturation) relationships by comparing with previous experimental studies. The predicted thermal conductivities were found to be in a good agreement with the experimental data collected from both this study and the other literatures with at least 85% confidence interval. It is concluded that the proposed model accounts for the effects of both environmental factors (i.e., moisture content and dry density) and compositional factors (i.e., quartz content and soil type) on soil thermal conductivity, and it has a great potential in predicting soil thermal conductivity more accurately for geothermal applications. 相似文献
19.
Experimental study on unfrozen water content and soil matric potential of Qinghai-Tibetan silty clay 总被引：3，自引：1，他引：2
Zhi Wen Wei Ma Wenjie Feng Yousheng Deng Dayan Wang Zhaosheng Fan Chenglin Zhou 《Environmental Earth Sciences》2012,66(5):1467-1476
A new soil moisture content sensor coupled with a new matric potential sensor that can operate in the subfreezing environment was used to measure the moisture content and soil matric potential dynamics of Qinghai-Tibetan silty clay. Combined with nuclear magnetic resonance (NMR) technique and thermal resistor temperature probe, the characteristics of unfrozen water content and soil matric potential, and their relationships with temperature were analyzed. The results show that initial water content has an impact on the freezing point and unfrozen water content. The decrease in the initial water content results in a depression in the freezing point. The Qinghai-Tibetan silty clay has more similar unfrozen water content characteristic to clay than to silt. There is approximately 3% of unfrozen water content retained when the soil temperature drops to −15°C. The change of soil matric potential with temperature is similar to that of the unfrozen water content. The matric potential value of the saturated silty clay is approximately −200 kPa when the soil temperature drops to −20°C. The measured matric potentials are significantly lower than the calculated theoretical values based on the freezing point depression. Moisture migration experiment indicates that soil matric potential controls the direction of moisture movement and moisture redistribution (including ice and liquid water) during the soil freezing. 相似文献
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基于相似材料配比的正交试验方案,制备了不同成分和配合比的相似材料试样,量测了各试样的导热系数值,研究了相似材料中含水率、胶结物及砂胶比等变化对导热系数量值的影响。研究结果表明:由于水和空气的导热系数差异较大,试样中含水率变化对导热系数量值的影响显著; 胶结物在试样中所占比例小,其成分因水化引起的孔隙率变化有限,胶结物成分和配比变化对导热系数量值的影响可以忽略; 受砂与胶结物之间的相互作用,胶结物成分和配比方案将改变砂胶比对导热系数量值的影响。当胶结物成分为石灰和石膏时,影响导热系数值的因素依次为含水率、砂胶比和胶结物,并随着砂胶比的增大,导热系数值在增加,但增幅逐渐减小; 当胶结物成分为水泥和石膏时,影响导热系数值的因素依次为含水率、胶结物和砂胶比,但随着砂胶比的增大,导热系数量值变化可以忽略。 相似文献