软土地基上高速公路路基扩建加宽中的关键问题研究

高速公路路基扩建加宽问题是现阶段高速公路建设过程中面临的重要问题之一。本文主要分析软土地基上高速公路路基扩建加宽中涉及的关键问题。     

筏板基础下碎石桩改良软土地基性能的数值研究

为解决传统碎石桩加固软土地基研究中忽视碎石桩侧向膨胀的问题,在对筏板基础下碎石桩排水荷载条件下加固软土地基的性能进行评估的基础上,利用PLAXIS 3D数值模拟方法研究了桩间距、直径和桩长等参数对筏板基础长期性能的影响,同时分析了各参数对筏板基础整体沉降、弯矩和碎石桩侧胀的影响。结果表明：1）软土中碎石桩的存在显著降低了筏板基础的沉降和弯矩;2）碎石桩的侧向胀形分布取决于其位置的深度;3）筏板基础的沉降、弯矩和侧向胀形随着间距与桩径比的减小、面积置换率和碎石桩长度的增加而增加;4）采用长厚比为0.75的碎石桩加固软土,可以达到良好的加固效果。研究结果对于全面了解筏板基础下碎石桩改良软土的侧胀性状具有重要意义,对于今后类似工程加固设计具有参考借鉴价值。     

排水固结法在高等级公路软土路基处理中的应用

文章结合广东省东莞市虎门港西大坦港区道路工程第二合同段K3+539～K3+860段软土路基具体工程实践,从工程技术、造价、工期及环境保护等方面进行分析,对简单、经济的排水固结法的应用及施工工艺做了较为详尽的阐述。     

淤泥固化技术的研究综述

随着环境整治工作的不断深入,淤泥的大量产生已经成为不可避免的事实。面对我国人口增长与耕地减少的矛盾,淤泥的开发是解决矛盾的有效途径。因此淤泥的开发利用是最有价值的潜在资源,淤泥的固化技术有很大的发展前景。     

Impacts of Low-Cost Land Certification on Investment and Productivity

New land reforms are again high on the policy agenda and low-cost, propoor reforms are being tested in poor countries. This article assesses the investment and productivity impacts of the recent low-cost land certification implemented in the Tigray region of Ethiopia, using a unique household and farm-plot-level panel data set, with data from before and up to eight years after the reform. Alternative econometric methods were used to test and control for endogeneity of certification and for unobserved household heterogeneity. Significant positive impacts were found, including effects on the maintenance of soil conservation structures, investment in trees, and land productivity.     

利用粉煤灰生产农用肥

粉煤灰可以直接用作肥料还可用来制作多种肥料.本文总结了目前各种粉煤灰肥料的特点和生产方法,对生产、作用机理进行了分析,简单论述了粉煤灰肥料的应用方法,最后提出了应注意的问题.     

生物聚合物改良玄武岩残积土崩解特性研究

为提高玄武岩残积土的抗崩解性及其边坡水稳性,利用生物聚合物瓜尔胶改良玄武岩残积土。在干湿循环条件下开展不同掺量瓜尔胶改良玄武岩残积土的崩解试验,观察残积土崩解过程,并对残积土改良土崩解系数和平均崩解速率进行测定,分析瓜尔胶掺量及干湿循环次数对玄武岩残积土水稳性的影响。研究结果表明：瓜尔胶可有效增强玄武岩残积土的抗崩解性能,随着瓜尔胶掺量的增加,改良玄武岩残积土的崩解系数和平均崩解速率呈现先减小后增加的特点,在瓜尔胶掺量为1.0%时抗崩解性能最佳;瓜尔胶掺量一定时,改良玄武岩残积土的崩解系数和平均崩解速率随着干湿循环次数的增加呈现增长趋势,当干湿循环次数N=4时,土体崩解率为N=1时的8倍。由此可见,瓜尔胶作为一种新型、环保的残积土边坡防护材料,可有效提升玄武岩残积土的抗崩解性能。研究结果为生态环保处置玄武岩残积土提供了新的思路,可为玄武岩残积土地区边坡工程的绿色发展提供参考。     

Reduced tillage and nitrogen effects on soil water dynamics and maize (Zea mays L.) yield under semi-arid conditions

Soil water and nutrients are critical drivers of crop production for smallholders of southern Africa. A three-year study was conducted to assess the effect of integrating single and double ploughing, ripping and planting basins with nitrogen fertilizer (0, 10 and 20?kg?N?ha^–1) on soil water dynamics and maize (Zea mays L.) yields. The experimental design was factorial with four tillage methods and three nitrogen levels as treatment factors. The study was conducted under semi-arid conditions of Zimbabwe. Tillage methods had similar soil water patterns in the profile and no tillage?×?N interaction effects were observed on soil water dynamics. Soil water penetrated deeper into the profile under ripper and basin methods than conventionally ploughed treatments. Nitrogen increased maize yields (14–96%) and rainwater-use efficiency (20–92%) regardless of tillage methods and growing season quality. However, more studies are required to explore complementary techniques that can improve rainwater capture and prolong soil water storage, and improve soil fertility.     

大兴安岭森林火烧对土壤生境质量影响研究

森林火烧是一种自然或人为因素产生的干扰,能够改变当地土壤的物理性质、化学性质及生物指标,对土壤的性质与土壤的肥力影响较大,对农业生态系统的结构与功能影响深远。作为我国重点的国有林区,大兴安岭地区林地面积广阔,森林覆盖率高,是我国生态安全的重要保障区,拥有丰富的林业资源,林下适生农业经济作物有500多种,林木、柞蚕、林果及中草药等绿色种养产业的资源十分丰富,是当前大兴安岭发展现代农业的主要模式。大兴安岭是我国森林火灾的多发区,文章对近年来国内专家学者对火烧影响森林土壤的理化性质与生物指标等众多研究成果进行综合评述,近年来,研究者从大兴安岭不同地区、不同林火种类与林火强度系统分析并研究了火烧对土壤生境质量的影响,该文通过对其进行归纳总结,旨在为该地区的火烧迹地植被恢复及农业林下经济的科学经营管理提供科学依据。