共查询到20条相似文献，搜索用时 234 毫秒
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在高层建筑工程施工中,地基处理是较为重要的一个环节。针对不同的施工因素、地质环境和经济状况都有着不同的地基处理方式,但是有关的书籍和规范不可能把复杂多变的地基处理中各种问题尽收眼底。因此,在建筑工程中地基的处理上,往往要根据施工中的实际情况进行分析,拟定出合理的解决方法。 相似文献
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介绍在工程施工中遇到软土地基时采用砂桩设计与施工的处理方法，该设计与施工具有简捷方便、打设设备轻型化、施工速度快、工程造价低等优点，是一种比较理想的软土地基处理方法。 相似文献
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指出了环保式清淤技术是在普通清淤方法的基础上发展起来的一种新型技术,技术的主要特征是在挖泥船上装配了专用的环保绞刀头,是一种可以高精度挖除水下污染底泥,而对周围扰动最小的新型绞刀。当清淤深度发生变化时通过绞刀水平调节器,使绞刀始终保持水平状态。清淤时绞刀外罩底边平贴河床,绞刀密封罩将绞刀扰动范围内的淤泥有效封盖并通过泥泵充分吸入。通过环保式清淤技术在南淝河清淤工程中的应用,结果表明:与常规清淤方法相比,环保式清淤降低了施工过程中因疏浚造成二次污染程度。 相似文献
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结合南京聚宝山公园一期工程地基处理的实例,介绍采用强务法处理大面积杂填土地基的设计方法。重点阐述采用强夯法处理地基时,如何根据工程实际地质情况合理的确定强夯法的有效加固深度、夯击能量、夯击遍数、夯击点布置形式及夯击点间距。针对强夯法施工效果检验和测试试验数据,对加固效果进行了分析和评价,表明强夯法进行地基处理能取得良好的社会和经济效益。 相似文献
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作者介绍了软弱地基上的基础设计与几种施工类型。强调指出根据软弱地基的种类不同,从设计到施工应采取不同的处理方法。 相似文献
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软土地基具有天然含水量大,高压缩性,强度低和承载能力低等工程特性,如果对此技术处理不当会给人们的生命和财产安全造成严重的威胁,从勘察到设计、施工,在每个建设环节中软土地基的处理都属重中之重。本文从设计和施工规范入手,简要介绍了三种常用的软土地基处理方法(即换点垫层法、预压法和水泥土搅拌桩复合地基法),并介绍这三种方法的适用性和工程中应注意的问题。 相似文献
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B. Vanlauwe S. Aman K. Aihou B. K. Tossah V. Adebiyi N. Sanginga O. Lyasse J. Diels R. Merckx 《Agroforestry Systems》1998,42(3):245-264
In cropping systems with limited amounts of external inputs, the soil organic matter pool (SOM) may contribute significantly to plant nutrition. The impact of organic inputs on total SOM and particulate organic matter (POM) N contents as affected by soil type and the relationships between sources of N and maize N uptake were assessed for a set of alley cropping trials in the West- African moist savanna. The trials were established in Niaouli (Bénin Republic), in Glidji, Amoutchou, and Sarakawa (Togo), and in Bouaké and Ferkessédougou (Côte d‘ Ivoire). The total soil N content, averaged over all treatments and years, varied between 324 and 1140 mg N kg?1 soil. The POM-N content varied between 50 and 160 mg N kg?1 soil. The average proportion of soil N belonging to the POM pool ranged between 9% and 29%. This was significantly related to the annual N inputs from maize stover and prunings, when averaged over the different alley cropping treatments. The trial ‘age‘ also appeared to be related to the impact of the different treatments on the POM-N content. The Ferkessédougou soil contained a relatively higher proportion of total soil N in the POM pool because of its relatively high silt and clay content, compared to the other sites. The relative change in POM-N content between 1996 and the initial sampling was about twice the relative change in total soil N content. This suggests that N incorporated in the POM is relatively labile, compared to N incorporated in the other SOM fractions. Maize N uptake was related to the amount of add pruning-N (partial r2 of 27%), the rainfall during the growing season (partial r2 of 17%), the POM-N content (partial r2 of 14%), and to a lesser degree to the POM N concentration (partial r2 of 5%), the fertilizer N addition rate (partial r2 of 3%), and the silt and clay content of the soil (partial r2 of 3%). The POM-N content was shown to be influenced by organic matter additions and soil characteristics and to contribute significantly to maize N supply. This pool may be an important indicator for the soil fertility status of savanna soils. 相似文献
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选取农田、撂荒草地、人工乔木林、人工灌木林和次生林5种不同土地利用类型土壤颗粒为研究对象,采用Microtrac S3500激光粒度仪测定土壤样品粒径,利用土壤分形学理论和方法,分析不同土地利用类型对土壤颗粒组成及其分形特征的影响。结果表明,土壤粒径在不同土地利用方式下存在显著差异,其中撂荒草地以砂粒为主,农田、人工乔木林、人工灌木林和次生林以粉粒为主;次生林、人工乔木林黏粒体积分数最大,且显著大于其他土地利用类型,撂荒草地最小;次生林、人工乔木林、人工灌木林粉粒体积分数最大,且显著大于农田与撂荒草地;砂粒体积分数则与粉粒相反。土壤分形维数的大小依次为撂荒草地＜农田＜人工灌木林＜次生林＜人工乔木林;土壤分形维数与土壤黏粒含量、粉粒含量均呈显著正相关,与土壤砂粒含量呈显著负相关。 相似文献
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Dario A. Fornara Rodrigo Olave Paul Burgess Aude Delmer Matthew Upson Jim McAdam 《Agroforestry Systems》2018,92(4):1035-1046
Multi-functional silvopastoral systems provide a wide range of services to human society including the regulation of nutrients and water in soils and the sequestration of atmospheric carbon dioxide (CO2). Although silvopastoral systems significantly contribute to enhance aboveground carbon (C) sequestration (e.g. C accumulation in woody plant biomass), their long-term effects on soil C pools are less clear. In this study we performed soil physical fractionation analyses to quantify the C pool of different aggregate fractions across three land use types including (1) silvopastoral system with ash trees (Fraxinus excelsior L.), (2) planted woodland with ash trees, and (3) permanent grassland, which were established in 1989 at Loughgall, Northern Ireland, UK. Our results show that 26 years after the conversion of permanent grassland to either silvopastoral or woodland systems, soil C (and N) stocks (0–20 cm depth) did not significantly change between the three land use types. We found, however, that permanent grassland soils were associated with significantly higher C pools (g C kg?1 soil; P < 0.03) of the large macro-aggregate fraction (> 2 mm) whereas soil C pools of the micro-aggregate (53–250 μm) and silt and clay (< 53 μm) fractions were significantly higher in the silvopastoral and woodland systems (P < 0.05). A key finding of this study is that while tree planting on permanent grassland may not contribute to greater soil C stocks it may, in the long-term, increase the C pool of more stable (recalcitrant) soil micro-aggregate and silt and clay fractions, which could be more resilient to environmental change. 相似文献
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长江上游部分地区土壤侵蚀与机制探讨 总被引：3，自引：0，他引：3
通过调查、定位与半定位观测,研究了长江上游不同地貌类型区的土壤侵蚀空间分布格局,以及各影响因子与土壤侵蚀间的关系。揭示了泥沙运行机制和水土流失规律,提出了小流域泥沙运移的输移比:流域面积小于5km~2,用0.6～0.7作为泥沙输移比;小于30km~2,用0.3～0.4作为输移比,推算流域土壤流失量,并建立了坡面和小流域土壤流失预报模型。 相似文献
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喀斯特不同侵蚀场地土壤颗粒分布及可蚀性特征 总被引：2，自引：0，他引：2
选取西南喀斯特最为典型的坡地、洼地和落水洞为研究单元,采用野外调查采样与室内试验相结合的方法,研究坡地、洼地和落水洞土壤颗粒的分布规律和土壤可侵蚀性特征。结果表明:土壤颗粒的质量分数分布,坡地为砂粒(42.25%)>粉粒(36.33%)>黏粒(21.42%);洼地为粉粒(51.80%)>砂粒(32.61%)>黏粒(15.59%);落水洞为粉粒(51.65%)>砂粒(31.67%)>黏粒(16.68%),坡地以砂粒为主,洼地和落水洞以粉粒为主。土壤可侵蚀性K值变化范围:坡地为0.07~0.22,洼地和落水洞分别为0.26~0.33和0.25~0.32,坡地土壤抗侵蚀能力强于洼地和落水洞。土壤分形维数与砂粒含量呈负相关,与粉粒含量呈正相关,与黏粒含量呈显著正相关。土壤可侵蚀性K值与砂粒和黏粒含量呈负相关,与粉粒含量呈显著正相关。土壤侵蚀沉积易形成质地较细,结构良好的土壤,但形成的土壤抗侵蚀能力较弱,易发生二次水土流失。 相似文献
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香格里拉亚高山大果红杉—高山栎群落种子雨与土壤种子库研究 总被引：1，自引：0，他引：1
采用随机取样的方法对香格里拉亚高山大果红杉、高山栎群落的种子雨和土壤种子库进行分析研究,结果表明,群落的种子雨由5个主要组成树种的种子组成,发生在每年的9~11月,强度为3 520粒/m2.土壤种子库由分属9科15属的17种植物组成,主要以多年生草本为主,且大约75%的种子均分布在较浅的土层.土壤种子库的物种组成与地上植被物种组成的相似性系数仅为0.042 6,表明土壤种子库与地上植被的相关性不明显. 相似文献