排序方式: 共有26条查询结果,搜索用时 15 毫秒
11.
12.
Ettringite related swelling in lime-stabilized sulphate bearing clay soil systems has only been reported within the last decade although similar expansive behaviour has been reported in concrete over many years. The use of ground granulated blastfurnace slag (GGBS), an industrial by-product, is well established as a binder in many cement applications where it provides enhanced durability and high resistance to sulphate attack. This paper reports on efforts to extend the use of GGBS to highway and other foundation layers by determining the beneficial effect of the suppression of swelling of lime-stabilized clay soils, particularly in the presence of gypsum. The paper describes the results of laboratory tests on lime-stabilized kaolinite containing different levels of added gypsum and on lime-stabilized gypsum (selenite) bearing Kimmeridge Clay to which, in both cases, the lime has progressively been substituted with GGBS. The tests determine the linear expansion behaviour of compacted cylinders, during moist curing in a humid environment at 30°C and during subsequent soaking in de-ionized water. The results illustrate that substitution of lime with GGBS produces significant reduction in linear expansion of lime-stabilized clay soils particularly those containing gypsum. 相似文献
13.
Mitigation of Iron Toxicity and Iron,Zinc, and Manganese Nutrition of Wetland Rice Cultivars (Oryza sativa L.) Grown in Iron‐Toxic Soil 下载免费PDF全文
14.
Effect of climate change on the trends of evaporation of phreatic water from bare soil in Huaibei Plain,China 总被引:1,自引:0,他引:1 下载免费PDF全文
When the soil condition and depth to water table stay constant, climate condition will then be the only determinant of evaporation intensity of phreatic water from bare soil. Based on a series of long-term quality-controlled data collected at the Wudaogou Hydrological Experiment Station in the Huaibei Plain, Anhui, China, the variation trends of the evaporation rate of phreatic water from bare soil were studied through the Mann-Kendall trend test and the linear regression trend test, followed by the study on the responses of evaporation to climate change. Results indicated that in the Huaibei Plain during 1991-2008, evaporation of phreatic water from bare soil tended to increase at a rate of 5% on monthly scale in March, June and July while in other months the increase was minor. On the seasonal basis, the evaporation saw significant increase in spring and summer. In addition, annual evaporation tended to grow evidently over time. When air temperature rises by 1 °C, the annual evaporation rate increases by 7.24–14.21%, while when the vapor pressure deficit rises by 10%, it changes from-0.09 to 5.40%. The study also provides references for further understanding of the trends and responses of regional evapotranspiration to climate change. 相似文献
15.
Dry soil mix (DSM) columns can be used to reduce the settlement of embankments constructed on soft clays and to improve the stability. During construction the shear strength of the columns needs to be confirmed for compliance with technical assumptions. However, the measurement of the column shear strength can be a contentious issue. All methods of assessing the ultimate shear strength of DSM columns have limitations. These are caused by uncertainties in empirical probe factors required to convert pullout or push in force measured during the lime column penetration test to shear strength and/or testing a small proportion of the DSM column volume and determining whether it is representative of the strength of the entire column. The penetration resistance measured using the lime column test is considered to be more representative of average column shear strength than some other test types. This test can be carried out as a pullout resistance test (PORT) or a push in resistance test (PIRT). Both PORT and PIRT require empirical correlations of measured resistance to an absolute measure of shear strength, in a similar manner to the Piezocone test. In this paper, finite element techniques developed for assessment of T-bar, Ball and Piezocone penetration tests , and are used to assess bounds for the empirical probe factor, N. To simulate the cemented DSM columns, analyses have incorporated a model for a strain softening material. Measured settlements from an embankment constructed on DSM ground improvement are then compared with finite element calculations to infer the shear strength of the columns. These inferred shear strengths are then compared with the results of PORT tests performed beneath the embankment. 相似文献
16.
Different sources of lime for the production of precipitated calcium carbonate were studied. The reactivity of lime, its optical properties and those of the final products are reported and discussed, and a comparison made between lime from different sources. The influence of the temperature of hydration water on the optical properties and particle sizes after hydration and precipitation was also studied. It was found that coarser granulations of lime have better optical properties than finer granulations. The hydration temperature does not have an appreciable impact on the optical properties, but influences the intermediate, i.e. the calcium hydroxide particle sizes and subsequently the particle sizes of the precipitated calcium carbonate. Furthermore, the maximum temperatures of lime hydration from different European sources do not vary significantly, but they differ in the kinetics of the hydration process. 相似文献
17.
In this project, an in situ soil treatment technique using the principles of electrokinetics was tested using laboratory experimental
models in order to identify the potential of this approach in modifying and reinstating the physical properties of salt affected
soils. Experiments were conducted in the laboratory using saline-sodic soils collected from two salt affected regions in central
Victoria, Australia. Soil specimens were compacted in glass tanks to reproduce in situ density and in situ water content.
Using mild steel electrodes inserted into the soil, a direct current was passed through the soil under a constant potential
gradient of 0.5 V/cm for a period of 14 days. In separate experiments, distilled water and a saturated lime solution were
introduced to the soil via the anode over this experimental period. It was observed that the soil dispersion, otherwise known
as soil sodicity (measured as ESP—Exchangeable Sodium Percentage and SAR—Sodium Absorption Ratio) decreased by up to 90% in
most regions of the soil between the electrodes. The compressive strength of the soil increased in excess of 100% with electrokinetic
treatment alone while the lime-enhanced electrokinetic treatment led to an almost 200% strength increase. The liquid limit
and plastic limit of the soil increased causing the plasticity index to decrease, indicating increases in soil compressive
strength and workability. These results indicate the potential of this technique for improving the physical properties of
salt affected soils both effectively and efficiently, and in particular gives hope for the remediation of salt affected land
for infrastructure management and development. 相似文献
18.
Brenda M. Miskimmin William F. Donahue Dainna Watson 《Aquatic Sciences - Research Across Boundaries》1995,57(1):20-30
Calcium hydroxide (Ca(OH)2), or hydrated lime, has recently been reintroduced in western Canada as a treatment to reduce macrophytes and algae in eutrophic waters. We examined the effects and recovery of aquatic invertebrates of the Ca(OH)2 treatment (250 mg L–1) of one half of a divided eutrophic pond compared to the untreated half. Nine weeks following treatment, total invertebrates on the untreated side were present at 1917 ± 555 individuals m–2, and on the treated side at 822 ± 186 individuals m–2. Notably, Chironomidae represented 13% of invertebrates on the untreated half, but dominated numerically with 72% on the treated half of the pond. The remaining five most abundant taxa in the untreated side were 88%–99% less abundant in the treated half of the pond. Diversity and evenness were twice as high for the untreated half as for the treated half of the pond. Because macrophytes were also extirpated with the Ca(OH)2 treatment, macrophyteassociated taxa were absent or at low numbers in the treated half. The death of organisms on the treated side of the pond may have been caused (directly or indirectly) by the pH shock associated with Ca(OH)2 treatments. Slow recolonization by most invertebrates during the year of treatment was probably due to the lack of heterogeneous macrophyte habitat. Follow-up sampling 3 years later indicated that the pond completely regained the abundance and biological diversity of flora and fauna. 相似文献
19.
Behavior of expansive soils stabilized with fly ash 总被引:6,自引:0,他引:6
Expansive soils cause serious problem in the civil engineering practice due to swell and shrinkage upon wetting and drying.
Disposal of fly ash, which is an industrial waste in both cost-effective and environment-friendly way receives high attention
in China. In this study, the potential use and the effectiveness of expansive soils stabilization using fly ash and fly ash-lime
as admixtures are evaluated. The test results show that the plasticity index, activity, free swell, swell potential, swelling
pressure, and axial shrinkage percent decreased with an increase in fly ash or fly ash-lime content. With the increase of
the curing time for the treated soil, the swell potential and swelling pressure decreased. Soils immediately treated with
fly ash show no significant change in the unconfined compressive strength. However, after 7 days curing of the fly ash treated
soils, the unconfined compressive strength increased significantly. The relationship between the plasticity index and swell-shrinkage
properties for pre-treated and post-treated soils is discussed. 相似文献
20.
Strengthening of contaminated materials using inorganic cementitious agents is becoming more widely used in the UK. The method has particular advantages for bulk fill operations such as highway earthworks. Research has been done into the chemical characteristics of leachates and leached solid samples from a study into the long-term durability of a lime strengthened silt/pfa mixture amended with sewage sludge. This involved determinations of chemical composition and mineralogy, and geochemical modelling using
. None of the heavy metals tested is present in the leachate at a concentration likely to pose a significant environmental threat, although some were present to a higher degree than expected based on the inorganic chemistry. This is ascribed to complexation of the heavy metals with dissolved organic matter. 相似文献