首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
含盐土导热系数的试验研究   总被引:14,自引:5,他引:9  
邓友生  何平  周成林 《冰川冻土》2004,26(3):319-323
室内试验表明, 含盐土的导热系数与其含盐成分(盐类)及含量有很大的关系. 同类土在含水量和干容重相同时, 在同一正温条件下粘土和砂土的导热系数是随氯化钠盐含量的增加而增大, 随硫酸钠盐含量的增加而减小; 在同一负温条件下, 无论何种土和含何种盐其导热系数均随含盐量的增加而减小, 含盐砂土和含硫酸钠盐土减小幅度显著. 硫酸钠盐土在含盐量相同时, 导热系数在负温区随温度升高而减小, 在正温区随温度升高而增大; 硫酸钠盐土在含盐量和温度相同时, 其导热系数随含水量的增加而增大.  相似文献   

2.
利用测温法和核磁共振法测量了不同浓度典型盐溶液(NaCl、Na2CO3)饱和重塑粉土的冻结温度及冻结特征曲线,并与不同浓度的NaCl、Na2CO3纯溶液作对比分析,研究初始含盐量对冻结温度及未冻水含量的影响。结果表明:土样冻结温度随初始含盐量的增加而逐渐降低;相同浓度NaCl溶液饱和土样的冻结温度低于相应纯溶液的冻结温度,但相同浓度 (<0.6 mol/L)Na2CO3溶液饱和土样的冻结温度却比纯溶液的冻结温度高;同一负温下,土样中未冻水含量随NaCl初始含盐量的增加而增多,但随Na2CO3初始含盐量的变化不明显。通过机制分析,表明盐类型和含盐量对土水势具有不同的影响。基于改进的广义Clapeyron方程,将含盐分土冻结温度表达式引入未冻水含量预测模型,得到了能够考虑不同含盐量影响的土体未冻水含量的定量表达,并与实测数据进行对比,验证了该模型能够较为合理的预测不同温度下含盐土体的未冻水含量。  相似文献   

3.
利用测温法和核磁共振法测量了不同浓度典型盐溶液(NaCl、Na_(2)CO_(3))饱和重塑粉土的冻结温度及冻结特征曲线,并与不同浓度的NaCl、Na_(2)CO_(3)纯溶液作对比分析,研究初始含盐量对冻结温度及未冻水含量的影响。结果表明:土样冻结温度随初始含盐量的增加而逐渐降低;相同浓度NaCl溶液饱和土样的冻结温度低于相应纯溶液的冻结温度,但相同浓度(0.6 mol/L)Na_(2)CO_(3)溶液饱和土样的冻结温度却比纯溶液的冻结温度高;同一负温下,土样中未冻水含量随NaCl初始含盐量的增加而增多,但随Na_(2)CO_(3)初始含盐量的变化不明显。通过机理分析,表明盐类型和含盐量对土水势具有不同的影响。基于改进的广义Clapeyron方程,将含盐分土冻结温度表达式引入未冻水含量预测模型,得到了能够考虑不同含盐量影响的土体未冻水含量的定量表达,并与实测数据进行对比,验证了该模型能够较为合理地预测不同温度下含盐土体的未冻水含量。  相似文献   

4.
黄土导热系数和比热容的实验研究   总被引:13,自引:0,他引:13  
王铁行  刘自成  卢靖 《岩土力学》2007,28(4):655-658
首先探讨了黄土导热系数和比热容的测试方法,组装形成黄土土样试验装置。然后取扰动黄土配制不同密度、不同含水量试样进行试验,测得黄土导热系数和比热容。实验结果揭示出,在含水量一定的情况下,导热系数和比热容随密度增大而增大;在密度相同的情况下,导热系数和比热容亦随含水量的增大而增大。进一步分析得到根据土体含水量、密度确定导热系数和比热容的关系式。相对于随密度的变化,黄土导热系数和比热容随含水量的变化尤为显著,含水量变化可以引起热参数较大的变化。  相似文献   

5.
为了研究干密度、含水率和NaCl含量对遗址土热劣化的影响,采用Hot Disk热常数分析仪对良渚遗址、交河故城遗址和通古斯巴西古城遗址的遗址土重塑样进行了热物理参数的测试,分别确定了遗址土的导热系数、热扩散系数和体积比热随干密度和含水率的变化关系。对通古斯巴西古城遗址重塑样掺入了不同含量的NaCl,研究了含盐量对遗址土重塑样导热系数的影响。结果表明,当含水率与干密度增加时,3种遗址土的导热系数均呈线性增长,热扩散系数和体积比热也随着含水率与干密度的增加而增大;相同条件下3种遗址土的热物理参数存在差异,良渚遗址的较大,交河遗址的较小,通古斯巴西古城的居中总体上与土中SiO2含量成正相关关系。当干密度与含水率一定时, 掺入NaCl增加了遗址土的导热系数。  相似文献   

6.
在室内用水平土柱吸渗法对不同含盐量、不同溶液浓度和不同土类的土壤水扩散系数进行了试验研究.试验结果表明:土壤水(或盐水)扩散系数与土壤的体积含水量之间具有指数函数的关系,且随着含水量的降低而减小.当同一类土在干容重和含水量相同时,土壤水扩散系数是随土中含盐量的增多而增大,以粗粒土最为明显.不同浓度的盐水在土壤中运行时,其盐水的扩散系数是随盐水浓度的增大而减小.  相似文献   

7.
含水率和干密度对黄土热参数影响的试验研究   总被引:1,自引:0,他引:1  
《岩土力学》2017,(3):656-662
黄土的热参数是黄土灾害成因机制研究及热工计算中的重要指标,而含水率和干密度对黄土的热参数具有一定的影响。对不同含水率、不同干密度黄土试样,采用Test Protocol Hot Disk TPS 2500S型热常数分析仪,在常温下开展热参数试验,探讨黄土热参数随含水率及干密度的变化规律。研究结果表明:黄土试样含水率一定时,干密度越大,其导热系数、比热容及热扩散系数也越大;黄土试样的导热系数和比热容随含水率的增大基本呈线性规律增大;当含水率较低时,热扩散系数随含水率的增大而增大;当达到一定含水率时,热扩散系数随含水率的增大而减小;继续增大含水率,热扩散系数趋于稳定。含水率对黄土热参数的影响程度大于干密度对其热参数的影响程度。在热工计算中,可根据土体含水率和干密度动态地选择热参数。  相似文献   

8.
为了研究高温巷道下围岩-隔热支护体系温度场的分布情况,基于围岩散热、能量守恒原理和异步长有限差分计算方法,建立了围岩-支护体系一维非稳态下的有限差分方程,编制相应解算程序,探讨了通风时间、围岩导温系数、温差、隔热层厚度和导热系数对围岩调热圈温度场的影响规律。研究结果表明:隔热层能延缓围岩散热和减少巷道风流对围岩的扰动,加快巷道降温;调热圈半径随通风时间增加、围岩导温系数增加、隔热层导热系数增加和厚度减少而增加。围岩温度梯度随通风时间增加而降低,随风流和原岩温差增大而增大;研究提高了对高温巷道调热圈特性及隔热结构的认知,对合理安排隔热支护有一定指导作用。   相似文献   

9.
盐渍土与盐溶液冻结温度关系的试验研究   总被引:4,自引:2,他引:2  
吴刚  邴慧  卜东升 《冰川冻土》2019,41(3):615-628
通过不同降温方式的冻结温度试验,明确了降温速率对土体冻结温度的影响,并采用快速降温方法,测定了不同含水率的三种天然氯(亚)盐渍土和黄土的冻结温度,以及不同浓度Na2SO4、NaCl溶液和由溶液配制的黄土的过冷温度和冻结温度,分析了降温速率、含水率、含盐量、盐类对土和溶液相变过程的影响。结果表明,快速降温得到的冻结温度值比缓慢降温得到的值偏低。当含水率低于盐渍土的塑限含水率时,水分是冻结温度的主要制约因素;当含水率大于土的塑限含水率时,天然盐渍土的含盐量对土的冻结温度起控制作用,Na2SO4含量控制含盐土的第一次相变,NaCl含量控制含盐土在低温下的第二次相变;低含盐量黄土含水率低于塑限含水率时,冻结温度随含水率增大而增大,但当含水率高于饱和含水率时,冻结温度随含水率变化不大。含Na2SO4的土和溶液的过冷温度变化规律与冻结温度变化规律类似,且其温度差值较小,通过Na2SO4溶液的冻结温度试验,可近似得到同浓度下含水率为16%只含Na2SO4黄土的冻结温度。  相似文献   

10.
借助GDS动三轴试验研究了不同负温下经历多次冻融循环后粉砂土的动应力、动模量、动模量比和阻尼比等动力参数的变化规律。试验发现,相同动应变下,冻融循环与动应力和动模量呈负相关性,而与动模量比和阻尼比呈正相关性,随着冻融次数增加,动应力和动模量都减小,动模量比和阻尼比都增大,通过回归分析分别给出了动模量比与动应变关系曲线和阻尼比与动应变关系曲线的归一化拟合模型。冻融循环对初始动模量和最大阻尼比影响显著。随着冻融次数增加,初始动模量减小,而最大阻尼比增大。分别对不同负温下冻融次数对初始动模量和最大阻尼比的影响进行了回归分析,提出了冻融次数修正系数的计算公式。结果表明,温度越低冻融循环对粉砂土动力特性影响越明显,经历5次冻融循环后的动力参数相对稳定,建议将5次冻融循环后的动力参数作为基本参数进行动力反应分析计算。  相似文献   

11.
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen.  相似文献   

12.
13.
Chronological analyses of correlations between certain global repeating events (mass extinctions of marine organisms, meteorite impacts, and flashes in the frequency of geomagnetic reversals) during the Phanerozoic Eon and the motion of the solar system in the Galaxy are presented for five rotationally symmetrical models for the regular Galactic gravitational field. Thirteen of sixteen mass-extinction events can be described by a repetition interval of 183±3 million years. This is in agreement with the anomalistic period (interval between two subsequent passages of the Sun through the apocenter of its Galactic orbit) in the model of Allen and Martos. The positions of the minima and maxima in Gaussian functions approximating the frequency distribution for geomagnetic reversals also agree with the times of passage of the Sun through the apocenter and pericenter, respectively, of its Galactic orbit in this model. The maximum in the distribution of the deviations of the dates of mass extinctions from the nearest dates of impacts of large, crater-forming bodies is close to zero, providing evidence that many such events are correlated. As a rule, extinctions follow impact events. The impacts of large bodies have occurred most often when the solar system passes through the Galactic plane, while mass extinctions occur more often at some distance from the Galactic plane (about 40 pc). As a rule, intervals of increases in the frequency of geomagnetic reversals coincide with dates of impacts of large bodies. At the same time, these intervals do not show a clear correlation with the dates of mass extinctions. The intensity of mass extinctions, like the energy released by impacts, is consistently higher in periods when the Sun is moving from the apocenter toward the pericenter of its orbit, than when it is moving from the pericenter toward the apocenter. Thus, there is evidence for a variety of relationships between repeating global events in the Phanerozoic and the motion of the Sun in the Galaxy. Long-period variations in the frequency of geomagnetic reversals are correlated with the orbital motion of the Sun, and increases in the frequency of geomagnetic reversals are correlated with impacts. Mass extinctions are correlated with the impacts of large bodies, whose motions may have been perturbed by clouds of interstellar material concentrated toward the Galactic plane and by the shock front associated with the Perseus spiral arm, through which the solar system passes. The velocity of the Sun relative to the spiral pattern is estimated.  相似文献   

14.
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″.  相似文献   

15.
从榴辉岩与围岩的关系论苏鲁榴辉岩的形成与折返   总被引:4,自引:1,他引:4       下载免费PDF全文
位于华北和扬子两板块碰撞带中的苏鲁榴辉岩形成的温压条件不但是超高压,而且是高温。榴辉岩的PTt轨迹表明其为陆-陆磁撞俯冲带的产物。榴辉岩的区域性围岩花岗质片麻岩为新元古代同碰撞期花岗岩,榴辉岩及其他直接围岩皆呈包体存在于其中,并见新元古代花岗岩呈脉状侵入榴辉岩包体中。区域性围岩新元古代花岗岩的锆石中发现有柯石英、绿辉石等包裹体,表明新元古代花岗岩的组成物质也经受过超高压变质作用,且榴辉岩与围岩新元古代花岗岩的锆石U-Pb体系同位素年龄基本相同。但新元古代花岗岩所记录的变质作用和变形作用期次(或阶段)却少于榴辉岩。椐上述可得如下推断:超高压榴辉岩与新元古代花岗岩岩浆是同时在碰撞带底部(俯冲板块前部)形成的;榴辉岩的第一折返阶段是由新元古代花岗岩岩浆携带上升的,其第二折返阶段是和新元古代花岗岩一起由逆冲及区域性隆起而上升,遭受剥蚀。  相似文献   

16.
某高速公路下伏煤矿采空区稳定性分析   总被引:10,自引:0,他引:10  
在论述某高速公路下伏砦脖煤矿采空区地质、采矿和工程地质特征的基础上, 进行了稳定性数值模拟分析, 定性与定量地分析与评价了该煤矿采空区的地表变形特征及稳定性。研究结果表明: 该煤矿采空区的变形尚未完成, 对拟建的高速公路将产生很大的危害, 必须采取相应的工程治理措施。   相似文献   

17.
摩擦桩基桩土间极限摩阻力取值问题探讨   总被引:1,自引:0,他引:1  
陈银生 《世界地质》1999,18(1):54-59
通过对广珠东线高速公路横沥大桥的试桩及土体的工程地质条件分析,总结出影响摩擦桩基桩土间极限摩阻力取值的一般问题以及解决问题的方法和措施。  相似文献   

18.
19.
We first re-examined the apparent polar wander curves for stable Eurasia and Africa since the Triassic. These curves were then combined together with curves of North and South America according to the kinematics of the Atlantic ocean and a synthetic polar wander curve was given. Then, most of the paleomagnetic results from the Tethys mobile belt, from the Atlantic to the Pamirs, were analysed.Several groups of plates, microplates and blocks can be seen. First, relatively stable regions like Maghreb and Sicily, which have not moved much. Then we have a group formed by Iberia, Sardinia, Italy and, to a lesser extent, Corsica and the Western and Central Alps. For these blocks, movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of Africa, but they are sometimes stronger.To the east, a major change takes place. The north of the Aegean Sea and the Ionian zone are clockwise rotated and these rotations are recent: Oligocene-Miocene for the first part, Pliocene to the present for the second part.A major problem arises in Turkey, Caucasus and Iran. Paleomagnetic results indicate a position far to the south of Eurasia, and, at the same time, geological evidence is in favour of a position close to Eurasia. We discuss these discrepancies.  相似文献   

20.
The structure of the eastern Pyrenees consists mainly of south-directed thrusts involving basement and cover rocks. An antiformal stack developed by the piling up of basement thrust sheets which outcrop in the Axial zone. These structures account for a thin-skinned thrust model rather than a vertical fault model in which the Axial zone would be essentially autochthonous, and the North-Pyrenean fault the axial plane of a fan thrust system. New data from the Eastern Pyrenees and the thin-skinned model suggest that(1) the structure east of the Pedraforca nappe is similar to that of the Central Pyrenees; (2) the cover rocks of the South-Pyrenean units and of the Axial zone-after restoration—built up a northwards-thickening prism consistent with the existence of a unique Pyrenean sedimentary basin during Mesozoic time; (3) the Axial zone is only a complex antiformal stack developed as a part of South-Pyrenean system related to the Paleogene thrusting-tectonics. The Axial zone palaeogeographic area had no special meaning during Mesozoic time.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号