冻融循环对兰州黄土渗透性变化的影响

在季节冻土区, 周期性的冻结与融化持续改变着土体内部结构, 土的孔隙率与渗透性也随之产生相应的变化. 针对这一现象进行了原状黄土和重塑黄土的冻融循环试验和冻融循环后的渗透试验. 结果显示: 随着冻融循环作用的进行, 原状黄土与重塑黄土干密度的变化趋势都是先增大后减小, 然后趋于稳定. 由于渗透系数与干密度呈负线性关系, 所以随着冻融循环次数的增加, 原状黄土与重塑黄土的渗透系数都是先减小后增大, 最后在4×10^-4~6×10^-4 cm·s^-1之间趋于一个稳定值. 因为重塑黄土是扰动土, 土结构中的颗粒大小较为均匀, 而原状黄土的土结构中颗粒大小不均匀, 导致重塑黄土的渗透系数始终大于原状黄土.     

冻融循环对黄土渗透系数各向异性影响的试验研究

为了反映冻融循环作用对原状黄土渗透各向异性及原状、 重塑黄土渗透差异的影响, 以西安Q₃黄土为研究对象, 通过三轴固结渗透试验对比分析了冻融前后水平、 竖直向原状黄土及重塑黄土的渗透系数随初始含水率、 围压、 冻融循环次数变化的规律。结果表明： 未冻融时各级围压下竖直向原状黄土的渗透系数为2×10^-6 ~ 18×10^-6 cm?s^-1, 水平向原状黄土和重塑黄土的渗透系数为0 ~ 4×10^-6 cm?s^-1; 经历冻融循环后, 水平、 竖直向原状黄土及重塑黄土的渗透系数与初始含水率的关系曲线分别呈现逐渐上升、 抛物线形式与变化平缓的不同特征, 而三者的渗透系数均随冻融循环次数的增加呈现数量级增大的趋势; 原状黄土的竖直 - 水平渗透系数比（k_v /k_h ）由冻融前的4.38逐渐减小到0.90, 可见冻融循环作用在显著提高黄土渗透性能的同时, 可以强烈弱化其各向异性特征。通过建立围压、 渗透系数与土体孔隙率的相关关系可知, 原状、 重塑黄土的孔隙率与围压存在极强的负线性相关性, 渗透系数随围压的增大呈典型指数衰减特征, 渗透系数与孔隙率具有相似的变化趋势, 因此冻融循环过程中土体孔隙率的改变是导致其渗透性质变化的主要原因。     

原状与重塑黄土冻融过程渗透特性对比试验研究

通过冻融条件下西安Q₃原状和重塑黄土的电镜扫描观测和三轴固结渗透试验,对比分析了冻融作用对原状和重塑黄土渗透特性的影响规律。结果显示:冻融条件下原状与重塑黄土微观结构均发生明显变化,土体胶结连接强度变差且颗粒排列更加松散,孔隙比增加,渗透性增强。冻融作用对原状和重塑黄土表面结构破坏均较严重,但原状黄土表面结构破坏程度较重塑黄土更为强烈;冻融过程产生的裂缝使得土中水分渗流和迁移的通道形成,导致原状与重塑黄土体渗透性增强。冻融条件下原状与重塑黄土渗透系数随含水率增加均先增大后减小,表现出抛物线变化特征;渗透系数随冻融次数增加均先增大然后趋于稳定,表现出指数增大特征;渗透系数随围压增大均先减小然后趋于稳定,表现出指数下降特征;相同条件下原状黄土渗透系数高于重塑黄土;原状与重塑黄土渗透系数差异随围压增大逐渐减小。     

冻融循环作用下黄土孔隙率变化规律

冻融循环作用通过破坏黄土颗粒的大小和土体的骨架及组构影响黄土的孔隙率. 通过颗粒分析实验发现冻融循环后土体颗粒有变小趋势,且集中分布在0.01～0.05 mm,在冻融10次后颗粒大小趋于稳定. 对经历冻融循环后的黄土进行压汞实验,发现随着冻融次数的增加,土体孔隙中的大孔径先减少,后增多;小孔径先增多,后减少,最后向5～10 μm范围内集中. 土的孔隙率也随冻融次数的增加而发生变化. 原状黄土的孔隙率在冻融5次时达到最小值,在冻融10次时达到最大值,冻融10次之后原状黄土的孔隙率在40%上下波动,达到稳定状态. 重塑黄土在冻融3次时孔隙率减少了6%并达到最小值,在冻融5次时孔隙率增加3%并达到最大值,最后在40%上下波动,达到稳定状态. 渗透系数的变化曲线与通过压汞实验获得的孔隙率变化曲线相似,印证了随着冻融次数的增加黄土的孔隙率呈先减小,后增大,然后趋于稳定的变化规律.     

应力路径试验前后不同黄土的孔隙分形特征

为了解不同黄土孔隙形状复杂程度的差异和应力路径对孔隙形状复杂程度的影响,对两种黄土应力路径前后孔隙分形特征进行了研究。首先比较了3种分维模型所得孔隙分形维数的可靠性,然后选用热力学关系模型,由进汞、退汞试验得到地裂缝区黄土、充填黄土初始样和三轴应力路径试验后的孔隙分布,据此分析了两种土体进汞孔隙和退汞孔隙分形维数的差异和受载后的分形维数变化,根据退汞过程仅管形孔内的汞流出及孔隙由管形孔和球形孔组成的假定,得到了应力路径试验前后孔隙形状的改变。结果表明,热力学关系模型得到的孔隙分形维数合理、可靠。初始状态,原状和重塑充填黄土的孔隙形状比原状和重塑黄土复杂;常规三轴试验后试样孔隙比减少,孔隙分形维数增加,球形孔向管形孔转变;相对于常规三轴压缩试验,减围压三轴压缩试验后试样的孔隙分形维数较小,管形孔占总孔隙的体积比例较少;总体上管形孔的分形维数比球形孔大,且基本不受应力路径的影响,其占总孔隙的体积比例随着试样宏观孔隙比的减少而增加。     

孔径分布对软黏土渗透特性的影响分析

用单向固结仪对取自不同地区的三种软黏土原状样和重塑样分别开展了固结渗透试验,得到不同土样的固结曲线和压缩曲线,推算土样在不同固结压力下的渗透系数。试验结果表明:相同应力时,土体的结构性使原状样的渗透系数明显大于相应重塑样的渗透系数,且随着固结压力的增大,两者的差距逐渐减小;原状样和重塑样的渗透系数与孔隙比的变化模式基本一致,但同一孔隙比下原状样的渗透系数大于相应的重塑样的渗透系数,比较浦东软黏土原状样和重塑样在相近孔隙比下的孔径分布曲线后确认:这是由于它们的孔径大小及分布存在明显差异引起的,且通过比较相同孔隙比下原状样和重塑样的大孔隙体积含量可合理地解释上述试验结果。最后,用简单表述土体的孔径大小及分布(土体的组构)的参考孔隙比e*10对多种软黏土的渗透指数Ck进行整理后,发现多种软黏土的原状样和重塑样均为一条相关度极高的ck-e*10直线,说明用参考孔隙比e*10可很好地反映土体的组构对软黏土渗透特性的影响。     

结构性软土渗透特性研究

本文对原状软土和重塑软土进行渗透特性试验,考察了饱和软土的渗透特性。原状样加载初期,渗透系数变化较小,当固结应力大于结构屈服应力时,渗透系数急剧下降,而结构屈服应力前后阶段的孔隙比与渗透系数对数坐标的直线关系没有发生变化,说明胶结对渗透性的影响较小。重塑土的渗透系数在加载过程中变化相对较小。试验结果表明,相同孔隙比时原状土渗透系数要明显大于重塑土。这是由于两者的组构不一样,即原状样的大颗粒和凝聚体间的大孔隙以及历史上形成的土颗粒的排列使其渗流通道要比重塑土通畅。用相同重塑方式制样得到的不同含水量土样,其渗透系数值相近;而用不同重塑方式制样得到的相近含水量土样,其渗透系数相差相对较大。确定饱和软粘土渗透性时要考虑孔隙比和组构的影响。     

马兰黄土孔隙结构参数与渗透性关系研究

利用改进的ZC-2015型渗气仪和TST-55型渗透仪进行马兰黄土渗气及饱和渗透试验,得到两个渗透性参数渗气率k_a和饱和渗透系数K_w,通过室内常规试验得到的孔隙比e,并利用图像处理软件（IPP）处理扫描电镜（SEM）照片得到的平面孔隙比e₀,结合试验结果并利用数学模型建立宏-微观孔隙参数与渗透参数之间的关系。结果表明:重塑土干密度增大,单位体积内颗粒数量增多,孔隙面积减少。原状风干土样埋深增大,大孔和中孔的孔隙面积、孔隙数量、孔隙平均直径明显减小;半对数线性模型可以消除K_w和k_a与孔隙结构参数在量级上的差异,拟合效果更好。lgK_w、lgk_a与e、e₀之间都呈现较好的线性关系;含水率变化时,渗气率拟合直线的斜率和截距的变化规律更明显。重塑土由于制样均匀,曲线的拟合度更高,而不同深度的原状黄土试样由于沉积过程造成的结构性的差异,致使其拟合度较重塑土偏低。     

黄土-古土壤饱和渗透性与孔隙分布特征关系研究

由于沉积环境的差异,古土壤较上覆黄土致密,其饱和渗透系数应低于黄土,但试验结果却显示二者的饱和渗透系数相近。为揭示这一现象的机理,在陕西泾阳南黄土塬开挖33 m的探井,沿井壁按1 m间距取黄土和古土壤原状试样,进行变水头渗透试验,测定试样的饱和渗透系数。同时用压汞试验（mercury intrusion porosimetry, MIP）及扫描电镜（scanning electron microscope, SEM）测试分别获取试样的孔隙分布曲线和微观结构图像,以分析黄土-古土壤饱和渗透性与孔隙分布特征的关系。结果表明：（1）黄土-古土壤地层的饱和渗透系数整体上沿深度方向规律性减小,但相邻黄土和古土壤层的饱和渗透系数无明显差异;（2）MIP及SEM测试结果表明,黄土结构均匀、孔隙大小较为一致,而古土壤具有不均匀的团块-裂隙结构,虽然团块内部较黄土致密,但团块间存在裂隙;（3）饱和渗透系数的大小取决于透水孔隙的体积分数,其中黄土的透水孔隙主要为较大孔隙（孔径>2 μm）,而古土壤的透水孔隙主要为团块间的微裂隙,虽然二者渗透系数相近,但渗透机理完全不同。为研究黄土与古土壤的孔隙分布特性和解决黄土区工程建设中的问题提供了理论依据。     

冻融循环作用下黄土无侧限抗压强度和微观规律的试验研究

青海地处多年冻土地区,属于青藏高原大陆性气候带,冻融循环是路基和地基基础的一种常见破坏因素,为研究冻融循环作用对青海地区实际工程的影响,揭示冻融循环作用对其损害的机理,通过对青海西宁地区原状黄土和重塑黄土进行冻融循环试验、无侧限抗压强度试验和电镜扫描试验,分析不同冻融温度和不同冻融循环次数对原状黄土、重塑黄土无侧限抗压强度和微观结构的影响。结果表明：当黄土经历0～6次冻融循环时,原状黄土和重塑黄土的强度逐渐降低,而8～10次冻融循环后其强度先增大后趋于稳定;原状黄土的强度随冻融温度降低而降低,而重塑黄土的强度随冻融温度降低先增大后减小;从微观角度分析,冻融温度的降低和冻融循环次数的增加,均导致黄土大颗粒逐渐分解为小颗粒,颗粒的排列方式发生改变。     

Unity of the national and the international in the socio-cultural development of the peoples of the USSR

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.     

Global repeating events in the history of the Earth and the motion of the Sun in the Galaxy

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.     

Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth

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″.     

从榴辉岩与围岩的关系论苏鲁榴辉岩的形成与折返

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。     

某高速公路下伏煤矿采空区稳定性分析

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。     

摩擦桩基桩土间极限摩阻力取值问题探讨

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。     

Paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic

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.     

On the consistency of proposed models for the Pyrenees with the structure of the eastern parts of the belt

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.