Studies regarding fibre-reinforcement are restricted to clays, silty and sandy soils. No information is available on gravels.
It is worth checking the effect of randomly oriented discrete fibres also on such soils to see if they can be beneficial and
to get a better insight into the grain to soil interaction mechanism. In this paper, the effect of a small amount of fibres
having high aspect ratio on a sandy gravel was analysed by means of tests carried out in a large triaxial apparatus. Specimens
of both natural and fibre-reinforced sandy gravel were prepared by wet tamping at different relative densities, and were tested
along monotonic and cyclic stress paths. The results show that the addition of a small amount of fibres causes a slight increase
in peak strength and a larger increase in ultimate strength at small confining stress, with an overall more ductile behaviour.
The cyclic tests at small confining stress and intermediate strain levels show that, for the lowest applied strain (of the
order of 10−2%), the stiffness was larger for the reinforced specimens, with a much sharper decrease at larger strains and final values
similar for the reinforced and non-reinforced materials. 相似文献
Tracking the migration of the CO2 plume is essential in order to better manage the operation of geologic sequestration of CO2. However, the large cost of most monitoring technologies, such as time-lapse seismic, limits their application. We investigated
the application of a probabilistic history matching methodology using routine measurements of injection data, which are affected
by the presence of large-scale heterogeneities, as an inexpensive alternative to track the migration of CO2 plume in an aquifer. The approach is demonstrated first through a synthetic example in which the ability to detect the presence
of flow barriers was tested. In a second example, we applied our method to the In Salah field, one of the largest geological
sequestration projects in the world, where the main direction of high permeability features was inferred. The accuracy and
reproducibility of the results show that our approach for assisted history matching is an economic and viable option for plume
monitoring during geologic CO2 sequestration. 相似文献
The Western Tropical Pacific(WTP) Ocean holds the largest area of warm water(28℃) in the world ocean referred to as the Western Pacific Warm Pool(WPWP),which modulates the regional and global climate through strong atmospheric convection and its variability.The WTP is unique in terms of its complex 3-D ocean circulation system and intensive multiscale variability,making it crucial in the water and energy cycle of the global ocean.Great advances have been made in understanding the complexity of the WTP ocean circulation and associated climate impact by the international scientific community since the 1960 s through field experiments.In this study,we review the evolving insight to the 3-D structure and multi-scale variability of the ocean circulation in the WTP and their climatic impacts based on in-situ ocean observations in the past decades,with emphasis on the achievements since 2000.The challenges and open que stions remaining are reviewed as well as future plan for international study of the WTP ocean circulation and climate. 相似文献
Airborne high–spatial resolution images were evaluated for mapping purposes in a complex Atlantic rainforest environment in southern Brazil. Two study sites, covered predominantly by secondary evergreen rainforest, were surveyed by airborne multispectral high-resolution imagery. These aerophotogrammetric images were acquired at four spectral bands (visible to near-infrared) with spatial resolution of 0.39 m. We evaluated different data input scenarios to suit the object-oriented classification approach. In addition to the four spectral bands, auxiliary products such as band ratios and digital elevation models were considered. Comparisons with traditional pixel-based classifiers were also performed. The results showed that the object-based classification approach yielded a better overall accuracy, ranging from 89% to 91%, than the pixel-based classifications, which ranged from 62% to 63%. The individual classification accuracy of forest-related classes, such as young successional forest stages, benefits the object-based approach. These classes have been reported in the literature as the most difficult to map in tropical environments. The results confirm the potential of object-based classification for mapping procedures and discrimination of successional forest stages and other related land use and land cover classes in complex Atlantic rainforest environments. The methodology is suggested for further SAAPI acquisitions in order to monitor such endangered environment as well as to support National Land and Environmental Management Protocols. 相似文献
This paper examines the effect of heavy tamping (dynamic compaction) on highly porous structured residual clayey soil. The aim of this study is to analyse the feasibility of this technique when applied on lightly bonded residual soil sites, which are commonly found in tropical and subtropical regions. This soil has some interesting characteristics, such as high fine grain soil percentages (56% clay and 22% silt), a plastic index of 11%, high porosity (initial void ratio of 1.21), high hydraulic conductivity (about 10?5 m/s) and a high stiffness at small strains (E?=?49.2-MPa). The research involves field [Cone Penetration Test (CPT) and the dynamic compaction] and laboratory (triaxial tests, characterization and hydraulic conductivity) investigation. According to laboratory tests, the void ratio decreased to 0.96, hydraulic conductivity decreased to 2.8?×?10?7 m/s, the effective peak friction angle (?′) increased from 30.5° (in natural conditions) to about 35.5°, and the triaxial stiffness at small strains decreased to E?=?20-MPa due to dynamic compaction. CPT results have shown an improved depth in which CPT tip strength (qt) increased from nearly 650-kPa to an average of 1700-kPa and CPT sleeve friction (fs) increased from approximately 50-kPa to about 130-kPa. Horizontal displacements were observed up to about 4.0 m of depth (approximately the same depth at which CPT results showed soil improvement). It was concluded that heavy tamping reduces soil voids and substantially increases soil strength, but also breaks soil structure and decreases soil stiffness. It is thus not a suitable ground improvement solution for highly porous structured residual clayey soil.
We analyze the variability of the ambient magnetospheric field along Titan's orbit at 20.3 Saturn radii. However, while our preceding study (Simon et al., 2010) focused on Cassini magnetometer observations from the 62 Titan flybys (TA-T62) between October 2004 and October 2009, the present work discusses magnetic field data that were collected near Titan's orbit when the moon was far away. In analogy to the observations during TA-T62, the magnetospheric fields detected during these 79 “virtual” Titan flybys are strongly affected by the presence of Saturn's bowl-shaped and highly dynamic magnetodisk current sheet. We therefore provide a systematic classification of the magnetic field observations as magnetodisk current sheet or lobe-type scenarios. Among the 141 (62 real+79 virtual) crossings of Titan's orbit between July 2004 and December 2009, only 17 encounters (9 real+8 virtual) took place within quiet, magnetodisk lobe-type fields. During another 50 encounters (21 real+29 virtual), rapid transitions between current sheet and lobe fields were observed around the moon's orbital plane. Most of the encounters (54=22 real+32 virtual) occurred when Titan's orbit was embedded in highly distorted current sheet fields, thereby invalidating the frequently applied idealized picture of Titan interacting with a homogeneous and stationary magnetospheric background field. The locations of real and virtual Titan flybys are correlated to each other. Each of the 62 real Titan flybys possesses at least one virtual counterpart that occurred shortly before or after the real encounter and at nearly the same orbital position. A systematic comparison between Cassini magnetometer observations from the real Titan flybys and their virtual companions suggests that there is no clear evidence of Titan exerting a significant level of control on the vertical oscillatory motion of the magnetodisk near its orbit. 相似文献
The La Costa pluton in the Sierra de Velasco (NW Argentina) consists of S-type granitoids that can be grouped into three igneous
facies: the alkali-rich Santa Cruz facies (SCF, SiO2 ~67 wt%) distinguished by the presence of andalusite and Na- and Li-rich cordierite (Na2O = 1.55–1.77 wt% and Li2O = 0.14–0.66 wt%), the Anillaco facies (SiO2 ~74 wt%) with a significant proportion of Mn-rich garnet, and the Anjullón facies (SiO2 ~75 wt%) with abundant albitic plagioclase. The petrography, mineral chemistry and whole-rock geochemistry of the SCF are
compatible with magmatic crystallization of Na- and Li-rich cordierite, andalusite and muscovite from the peraluminous magma
under moderate P–T conditions (~1.9 kbar and ca. 735°C). The high Li content of cordierite in the SCF is unusual for granitic rocks of intermediate
composition. 相似文献