Radiation exposure and Mission Strategies for Interplanetary Manned Missions (REMSIM)

Cosmic radiation is an important problem for human interplanetary missions. The “Radiation Exposure and Mission Strategies for Interplanetary Manned Missions–REMSIM” study is summarised here. They are related to current strategies and countermeasures to ensure the protection of astronauts from radiation during interplanetary missions, with specific reference to: radiation environment and its variability; radiation effects on the crew; transfer trajectories and associated fluences; vehicle and surface habitat concepts; passive and active shielding concepts; space weather monitoring and warning systems.     

1999年8月11日日全食期间的重力吸引效应研究

对1999年8月11日日全食阴影扫过欧洲期间,设在Annelles,Uccle,Walferdange和Bondy弹簧和超导重力仪的记录进行了分析.为了确定月亮对太阳万有引力可能的遮挡效应的极限,对超导和弹簧重力仪记录进行了比较.同时也对LCR和阿斯卡尼亚重力仪观测结果进行了讨论.结论是如果日食重力吸引效应存在,它应在超导重力仪±1 nm/s2(0.1×10-8ms-2)的观测精度范围之内.研究发现在以上情形下,弹簧和超导重力仪都在它们的精度范围内工作,并且日食引起的异常环境干扰可能使重力信号有重大的改变.     

Interpretation of aeromagnetic data across the central crystalline shield area of Nigeria

Summary. A residual map of the total magnetic field (above 25 000 nT base) is presented for a portion of the central crystalline shield area of Nigeria and overlapping small portions of the Chad basin and the Benue rift (8°30'−12° 00'lat, and 7°−10°30' long). The map (based on a dataset digitized from recently released aeromagnetic sheets of Nigeria) leads to four results. (1) A magnetic boundary, evident on the map, separates the Younger Granite complexes into two groups. The groups are petrologically different, and the boundary may be a fault line with uplift to the south. (2) South of the boundary the map is dominated by a system of sub-parallel anomalies striking NE–SW, possibly representing major tectonic trends, and a set of fractures through which the Younger Granite complexes were intruded. The trend of the system parallels the Benue rift and lineaments in the oceanic crust off West Africa. (3) Negative magnetic anomalies lie over most of the known ring complexes, and over some suspected buried ring complexes and other intrusions. (4) 2½-and 3-D modelling shows that the larger complexes extend to 12 km depth, and the smaller ones to 6 km. They have nearly vertical sides, and magnetization contrasts range from 0.3 to 0.5 A m⁻¹.     

Crustal and upper mantle structures of the brazilian coast

The Rayleigh wave phase and group velocities in the period range of 24–39 sec, obtained from two earthquakes which occurred in northeastern brazil and which were recorded by the Brazilian seismological station RDJ (Rio de Janeiro), have been used to study crustal and upper mantle structures of the Brazilian coastal region. Three crustal and upper mantle models have been tried out to explain crustal and upper mantle structures of the region. The upper crust has not been resolved, due basically to the narrow period range of the phase and group velocities data. The phase velocity inversions have exhibited good resolutions for both lower crust and upper mantle, with shear wave velocities characteristic of these regions. The group velocity data inversions for these models have showed good results only for the lower crust. The shear wave velocities of the lower crust (3.86 and 3.89 km/sec), obtained with phase velocity inversions, are similar to that (=3.89 km/sec) found byHwang (1985) to the eastern South American region, while group velocity inversions have presented shear velocity (=3.75 km/sec) similar to that (=3.78 km/sec) found byLazcano (1972) to the Brazilian shield. It was not possible to define sharply the crust-mantle transition, but an analysis of the phase and group velocity inversions results has indicated that the total thickness of the crust should be between 30 and 39 km. The crustal and upper mantle model, obtained with phase velocity inversion, can be used as a preliminary model for the Brazilian coast.     

Problems of soil and groundwater pollution in the disposal of “marble” slurries in NW Sicily

This work deals with disposal of slurries generated during the cutting and polishing processes of slabs of decorative sedimentary carbonate rocks in the north western Sicily. At present, they are used as fillers of dismantled quarries near the sawmills and, as a final step of reclamation, are covered with earth layers. In spite of such inexpensive solution, there is lack of knowledge about the composition of the waste. In order to assess if there is any threat for the environment and to suggest indications for alternative solutions, such as recycling or inactivation processes, the slurries were analysed by XR diffraction, simultaneous thermal analysis, ICP/MS, ionic chromatography, FTIR, UV-Vis, COD and TOC measurements, grain size analysis. Results indicate that the slurries can threaten the groundwater, because of the high chemical oxygen demand; furthermore they can modify the mechanism of groundwater recharge, because of their grain size distribution. Some laboratory tests show that, even in very aggressive conditions, the solid pollutants persist in the waste and slowly release into water the products of their degradation. The slurry therefore should be subjected to inactivation treatment before disposal or, alternatively, recycled as secondary raw material for a suitable process.     

Performance of Mortar and Chemical Grout Injection into Surrounding Soil When Slurry Pipe-jacking Method is Used

Small-diameter shallow tunnels are often being built by using the slurry pipe-jacking method. This system involves the pushing or thrusting of a drivage machine and concrete pipes into the ground. Chemical grout injection into the surrounding soil around the tunnel is carried out after the drivage and pushing processes are finished. The purpose of the chemical grout injection is to maintain permanent stability of the surrounding soil. However, the behavior of the chemical grouting material in the surrounding soil around the tunnel and the amount of optimum injection is not clearly understood. From these points of view, this paper discusses the performance of the chemical grouting material, when it is injected into the surrounding soil around the tunnel, by means of 2-D Eulerian–Lagrangian seepage analysis. Moreover, the effectiveness of the chemical grout injection was evaluated by using the non-linear finite element method. This investigation show when the range of the grouted zone is designed; it is necessary that the relationship between Young’s modulus of the soil/grouted zone and the confining stress be taken into consideration in order to establish effective, economical and safe chemical grout injection system. Understanding the performance of the seepage/dispersion behavior of the chemical grout and the characteristics of soil/ grouted zone is also important.     

Monitoring of Over Cutting Area and Lubrication Distribution in a Large Slurry Pipe Jacking Operation

Slurry pipe jacking was firmly established as a special method for the non-disruptive construction of the underground pipelines of sewage systems. Pipe jacking, in its traditional form, has occasionally been used for short railways, roads, rivers, and other projects. Basically the system involves the pushing or thrusting of concrete pipes into the ground by a number of jacks. In slurry pipe jacking, during the pushing process, mud slurry and lubricant are injected into the face and the over cutting area that is between the concrete pipes and the surrounding soil. Next, the slurry fills voids and the soil stabilizes due to the created slurry cake around the pipes. Fillings also reduce the jacking force or thrust during operation. When the drivage and pushing processes are finished, a mortar injection into the over cutting area is carried out in order to maintain permanent stability of the surrounding soil and the over cutting area. Successful lubrication around the pipes is extremely important in a large diameter slurry pipe jacking operation. Control of lubrication and gaps between pipes and soil can prevent hazards such as surface settlement and increases in thrust. Also, to find voids around the pipes after the jacking process, in order to inject mortar for permanent stabilizing, an investigation around the pipes is necessary. To meet these aims, this paper is concerned with the utilization of known methods such as the GPR (Ground Penetrating Radar) system and borehole camera to maintain control of the over cutting area and lubricant distribution around the pipes during a site investigation. From this point of view, experiments were carried out during a tunnel construction using one of the largest cases of slurry pipe jacking in Fujisawa city, Japan. The advantages and disadvantages of each system were clarified during the tests.     

国道219线新-藏公路改建工程地质灾害评价

国道219线新-藏区界至红土达坂路段全长109．55km。大部分路段穿越湖盆槽谷中央部位，部分线路沿湖盆边缘台地布设，海拔高度介于5000-5400m之间，地势平坦开阔，多年冻土发育，工程地质条件较差；现有公路路基高度低，几乎没有排水设施。冬季易产生路基冻胀和涎流冰危害，春、夏季因冻土融化，常引起路基沉陷和翻浆，严重危害公路运输安全甚至阻断交通。公路工程修建活动将极大地改变冻土环境，使天然状态下的水分循环发生改变，导致多年冻土退化，上限加深，进一步诱发冻胀、融沉、热融滑塌等冻土灾害，加剧风沙灾害、诱发公路边坡失稳破坏。在即将进行的公路改、扩建工程中，应采取保护冻土的设计原则，优选线路，加强侧向排水，合理设置取弃土场。     

Terrane assembly and geodynamic evolution of central–western Hoggar: a synthesis

After a review of the rock sequences and evolution of the eastern and central terranes of Hoggar, this paper focusses on the Neoproterozoic subduction-related evolution and collision stages in the central–western part of the Tuareg shield. Rock sequences are described and compared with their counterparts identified in the western and the eastern terranes exposed in Hoggar and northern Mali. The Pharusian terrane that is described in detail, is floored in the east by the Iskel basement, a Mesoproterozoic arc-type terrane cratonized around 840 Ma and in the southeast by Late Paleoproterozoic rock sequences (1.85–1.75 Ga) similar to those from northwestern Hoggar. Unconformable Late Neoproterozoic volcanosedimentary formations that mainly encompass volcanic greywackes were deposited in troughs adjacent to subduction-related andesitic volcanic ridges during the c. 690–650 Ma period. Abundant arc-related pre-collisional calc-alkaline batholiths (650–635 Ma) intruded the volcanic and volcaniclastic units at rather shallow crustal levels prior to collisional processes. The main E–W shortening in the Pharusian arc-type crust occurred through several stages of transpression and produced overall greenschist facies regional metamorphism and upright folding, thus precluding significant crustal thickening. It was accompanied by the shallow emplacement of calc-alkaline batholiths and plutons. Ages of syn-collisional granitoids range from 620 Ma in the western terranes, to 580 Ma in the Pharusian terrane, thus indicating a severe diachronism. After infill of molassic basins unconformable above the Pan-African greenschists, renewed dextral transpression took place in longitudinal domains such as the Adrar fault. The lithology, volcanic and plutonic suites, deep greenschist facies metamorphism, structures and kinematics from the Adrar fault molassic belt previously considered as Neoproterozoic are described in detail. The younger late-kinematic plutons emplaced in the Pharusian terrane at 523 Ma [Lithos 45 (1998) 245] relate to a Cambrian tectonic pulse that post-dates molasse deposition. The new geodynamic scenario presented considers several paleosubductions. The major east-dipping subduction, corresponding to the closure of a large Pan-African oceanic domain in the west (680–620 Ma) post-dates an older west-dipping “Pharusian” subduction (690–650 Ma?) to the east of the eastern Pharusian terrane. Such a diachronism is suggested by the 690 Ma old eclogites of the western part of the LATEA terrane of central Hoggar [J. African Earth Sci. this volume (2003)] that are nearly synchronous with the building up of the Pharusian terrane, thus suggesting that the 4°50^′ lithospheric fault represents a reactivated cryptic suture.