A new concept of pedogenic nodule formation in landscapes of the Russian Far East

The typification of ferromanganese nodules (FMN) formed in subaqueous and subaerial settings and in residual materials, as well as FMN localization in various sediments and soils, is discussed. The genetic diversity of morphologically similar FMN and the transformation of FMN-bearing complexes with changes in landscapes have been established.     

New basis for the constitutive modelling of aggregated soils

Natural and compacted soils are usually characterized by aggregation of particles. The mechanical behaviour of these materials depends on soil structure. The oedometric compression tests performed on aggregated samples presented here showed that these materials exhibit a yield limit depending not only on stress history and stress state but also on soil structure. Evidence is provided using the neutron tomography technique. These results revealed that soil structure modification occurs together with plastic deformations. The experimental results are used to propose a new state parameter to quantify the soil structure. Based on pore-scale experimental observations, an evolution law for this parameter is proposed as a function of associated plastic strains. Considering both soil fabric and inter-particle bonding effects, a new yield limit depending on stress state, stress history and soil structure is introduced for the aggregated soils. Accordingly, a new constitutive framework consistent with strain hardening plasticity is proposed to consider soil structure effects in the modelling of aggregated soils.     

Changing grading of soil: effect on critical states

Examples of situations are presented where the grading of a soil changes during its lifetime either by crushing of particles leading to an increase of fine material or by slow transport of fine particles with seepage leading to a decrease of fine material. Such grading changes influence the basic constitutive properties of the soil, in particular properties such as critical states which are dependent on the available range of densities of packing. Discrete element modelling is used to show the dependence of critical state conditions on grading and the way in which the particle assembly seeks out new critical state conditions as the grading changes.     

浅谈（TCP）射孔技术在松辽地区应用与发展

油管传佃式射孔是近几年来射孔新技术,应用于石油、天燃气勘探、开发井中。的使用,大大提高了油气井的射孔效率,增加油气产量,降低了作业成本,从而能获得较好的经济效益,解决了正压射孔存在的不足,是一项新的负压射孔方式。通过几年来在松辽地区的应用,效果很佳。大部分的高产油气流都是采用这种射孔方法进行的。     

RATIONAL UTILIZATION OF MOUNTAIN SOILS IN SOUTHEAST QINGHAI-XIZANG (TIBETAN)PLATEAU

ISoil-fo~gEnvironmentandMainSoilTrocsThesoLItheastQinghai-Xizang(Tibetan)PlateauwheretheHengduanMoUnains,eastempartoftheThmalayanandNyainqentanglhamoUnainsarelocatedextendsfrom25'to34"Nand92'to1O5'Ewithanareaof5OO,OOOkm',oraboutone-fiffooftheentireQinghai-XiZangPlateau.ItisatransitionalzoneofdeePdisseCtedmoUntainseXtendingsoutheastWardpenpherallowlandsandwichedin-betWeenSichuanBasinandcentralYunnanPlateau.Whletheterrainofthesmponinclinestosoutheast,thealtitudeofthevaIleysraises…     

Tectonometamorphic evolution of the Bohemian Massif: evidence from high pressure metamorphic rocks

The Variscan orogenic belt, of which the Bohemian Massif is a part, is typically recognized for its characteristic low pressure, high temperature metamorphism and a large volume of granites. However, there are also bodies of high pressure rocks (eclogites, garnet peridotites and high pressure granulites) which are small in size but widely distributed throughtout the Massif. Initially the high pressure rocks were considered to be relicts of a much older orogenic event, but the increasing data derived from isotopic and geochronological investigations show that many of these rocks have Palaeozoic protoliths. Metamorphic ages from the high pressure rocks define no single event. Instead, a number of discrete clusters of ages are found between about 430 Ma and the time of the dominant low pressure event at around 320–330 Ma.Most of the eclogite and granulite facies rocks are assigned to allochthonous nappes that arrived close to the end of the low pressure event, but before final granite intrusion. The nappes contain a mixture of different units and the relationship between rocks with high pressure relicts and host gneisses with no apparent signs of deep burial is still problematic. Some of the high pressure rocks retain evidence of multiple stages of partial re-equilibration during uplift. Moreover, it can be shown in certain instances that host gneisses also endured a multistage metamorphic development but with a peak event convergent with one of the breakdown stages in the enclosed rocks with high pressure relicts. It thus appears that the nappe units are composite bodies probably formed during episodic intracrustal thrusting. Fluids derived from prograde dehydration reactions in the newly under thrusting slab are taken to be the catalysts that drove the partial re-equilibrations.On the scale of the whole Massif it can be seen within the units with high pressure relicts that the temperature at the peak recorded pressure and that during the breakdown are variable in different locations. It is interpreted that regional metamorphic gradients are preserved for given stages in the history and thus the present day dismembered nappe relicts are not too far removed from their original spatial distribution in an original coherent unit. From the temperature information alone it is highly probable that the refrigerating underthrusting slab was situated in the north-west. However, this north-west to south-east underthrusting probably represents the major 380–370 Ma event and is no guide to the final thrusting that emplaced the much thinned nappe pile with high pressure relicts.Granite genesis is attributed to the late stage stacking, during the final Himalayan-type collision stage, of thinned crust covered by young, water-rich, sediments — erosion products of the earlier orogenic stages. Regional metamorphism at shallow depths above the voluminous granites was followed by final nappe emplacement which rejuvenated the granite ascent in places. Correspondence to: P. J. O'Brien     

施工顺序对软土地坪复合地基的影响探讨

场地回填土与搅拌桩施工顺序将直接影响软土地坪复合地基的处理效果,其中沉降控制是影响地坪安全运行的关键。以近海软土地区工业厂房水泥土搅拌桩复合地基工程为例,探讨了复合地基水泥土搅拌桩、回填土两种不同施工顺序的影响因素及相应处理效果;通过数值模拟试验,计算分析了不同填土厚度下两种工况的地基固结总沉降、施工沉降、工后沉降。结果表明,采用“先土后桩”的施工顺序的施工期沉降大于“先桩后土”,但工后沉降大大减小,提高了软土地坪地基处理效果,有利于处理后地坪的安全运行,验证了前述分析结论,为合理设计方案的确定提供了重要的参考依据。     

船式支护在基坑中的应用

在深厚软土地区的基坑,对基坑底软土进行搅拌加固形成强度较高的底板而保证坑底稳定,侧壁采用支护桩支护保证侧壁的稳定使其不倾倒,支护桩与加固底板两者共同作用形成的船状结构支护体系类似轮船的船侧壁及船底板,以保证基坑的稳定。结合具体的工程实例,介绍了船式支护的侧壁及底板的设计方法。工程案例成功实施,监测结果表明,船式支护既可避免支护桩嵌固深度过长,又利于软土的土方施工及工程桩的保护,是安全可靠的,对类似工程有一定的参考意义。     

Role of dykes in induced seismicity at Bhatsa reservoir,Maharashtra, India

The geological and hydrological conditions near the reservoir site play an important role in the generation or absence of seismic activity. Near Bhatsa reservoir, along the west coast of India intense seismic activity occurred during August–September 1983, after a lag of six years of initial impounding. From July 1983 to September 1990, 15,388 earthquakes (mostlyM ₁<3.0) were recorded, the largest being of magnitude 4.9. The spatial distribution of well located 172 earthquakes suggest a strong correlation between the epicenters and the disposition of dykes and faults around the Bhatsa region. It is inferred that these dykes have acted as barriers for the diffusion of water from the reservoir, thereby becoming zones of instability due to increased pore pressure not only along them but also over the volume they bound.     

Dynamics of Mars-orbiting dust: Effects of light pressure and planetary oblateness

This paper deals with dynamics of impact ejecta from Phobos and Deimos initially on near-circular equatorial orbits around Mars. For particles emitted in a wide size regime of 1 micron and greater, and taking into account the typical particle lifetimes to be less than 100 years, the motion is governed by two perturbing forces: solar radiation pressure and influence of Mars' oblateness. The equations of motion of particles in Lagrangian non-singular elements are deduced and solved, both analytically and numerically, for different-sized ejecta. We state that the coupled effect of both forces above is essential so that on no account can the oblateness of Mars are be neglected. The dynamics of grains prove to be quite different for the ejecta of Phobos and Deimos. For Deimos, the qualitative results are relatively simple and imply oscillations of eccentricity and long-term variations of orbital inclination, with amplitudes and periods both depending on grain size. For Phobos, the dynamics are shown to be much more complicated, and we discuss it in detail. We have found an intriguous peculiar behavior of debris near 300 µm in size. Another finding is that almost all the Phobos ejecta with radii less than 30 µm (against the values of 5 to 20 µm adopted earlier by many authors) should be rapidly lost by collisions with martian surface. The results of the paper may be the base for constructing an improved model of dust belts that presumably exist around Mars.