Acta Geotechnica - The spatial variation of the physical–mechanical properties of rock or rock-like materials is an intrinsic characteristic of the materials induced by multiscale material... 相似文献
Zonal distribution can be noticed in the gossans resulting from the weathering of siderite in carbonate strata, and this can be accounted for by zoning of subsurface waters. Since siderite is more insoluble than its hostrock, gossans are generally developed in the same place as siderite is exposed. Systematic variations in chemistry are recognizable from the ore body upwards to the surface. The gossans are high in Fe and Mn, but impoverished in S, P, Pb, Zn, Be, Cd, and Ag. This may serve as an indicator of distinguishing siderite gossans from sulphide ones in this region. 相似文献
Biogrouting is a new ground improvement method that has been studied in recent years. This method involves mainly the use of a microbially induced calcite precipitation process to bind soil particles to increase the strength or to fill in the pores of soil or joints of rock for seepage control. There are two major challenges in the use of biogrout for seepage control through rock joints. The first is how to inject the biogrout solutions, and the second is to understand the mechanisms for the formation of calcite under seepage flow. In this paper, a study on the injection of biogrout solution and the formation of precipitates along a circular 1D flow channel is presented. To minimize the influence of flow, a new one-phase injection method to inject bacterial solution and cementation agents simultaneously was adopted in this study. Factors affecting the formation and distribution of precipitates along the flow channel such as flow velocity, flow rate, and aperture of flow channel were investigated. The experimental results indicated that less calcite was precipitated at locations further away from the injection point due to depletion of the reactants’ concentrations along the flow path. Using the one-phase injection method, the bacterial activity had a major effect on the accumulation of the calcite on the inner surface of the flow channel. The total calcite precipitated on the surface of the flow channel increased slightly with increasing bacterial activity or flow rate. An equation to predict the distance travelled by the biosolution has been derived based on the testing results.
The components of the primary elements in the dune sands for the MGS1 subsec-tion of the Milanggouwan section in the Salawusu River valley, compared with those of mod-ern dune sands, show that they were caused by East Asian winter monsoon in the Mu Us desert during Holocene. The examined ages for the 11 layers of dune sands, based on the average sedimentary rate, are: 0 to 960, 1350–2240, 2470 to 3530, 4000 to 4180, 4290 to 4350, 4380 to 4760, 5040 to 5920, 6570 to 8270, 9020 to 9700, 9880 to 10160 and 10580 to 11080 a BP, respectively. The climatic events indicated by these dune sands are consistent with those records in the Huguangyan volcanic lake, Zoige peat bog, Hulu cave and Dunde ice core, particularly with the climatic fluctuations of the North Atlantic since 11 000 a BP. Among them, patterns from B0 to B8 correspond to the peak values of 0MD, 2D, 4D, 6D+8D+10D, 12D, 14D, 16D, 18D and 20D respectively. It might be caused by the North Atlantic ice age induced by the heat circulation, which strengthened the polar high pressure and Siberian-Mongolian high pressure and further led to the dominance of the winter mon-soon over China’s desert area. 相似文献
The upmost segment(Holocene series)of the Milanggouwan stratigraphic section(MGS1)in the Salawusu River valley shows 11 sedimentary cycles of dune sands and fluvio-lacustrine facies,or dune sands and paleosols.The analysis of the magnetic susceptibility of this segment suggests that there are 11 magnetic susceptibility cycles with the value alternating from low to high,in which the layers of the dune sands correspond to the lower value of the magnetic susceptibility and the layers of fluvio-lacustrine facies and paleosols correspond to the higher peaks.The study reveals that the low and high magnetic susceptibility values indicate the climate dominated by cold-arid winter monsoon and warm-humid summer monsoon of East Asia,respectively,and the study area has experienced at least 22 times of mil-lennial-centennial scales climate alternation from the cold-arid to the warm-humid during the Holocene.In terms of the time and the climate nature,the variations basically correspond to those of the North Atlantic and some records of cold-warm changes in China as well.They might be caused by the alternation of winter and summer monsoons in the Mu Us Desert induced by global climate fluctuations in the Holocene. 相似文献
Acta Geotechnica - Biocement as an alternative to cement for soil improvement has been studied for the past decade. A comparative study on the cementation effect on the mechanical behavior of sand... 相似文献