基于非饱和土压强度计算模型的土湿吸力物理模型试验分析

土湿吸力是水利工程设计重要指标,含水率是影响土湿吸力关键因素。结合土体含水率物理模型试验方式,基于非饱和土压强度计算模型推算土体不同含水率下的土湿吸力。试验成果表明:不同土体干密度下,含水率增加土湿吸力下降明显,当含水率达到25%时,土湿吸力下降特征最为明显,且含水率与土湿吸力的相关性最佳。随着土湿吸力的增加,土体抗剪强度逐渐增加,当土湿吸力在10~15MPa之间时,土体抗剪强度趋于稳定,土体干密度对抗剪强度也有所影响。     

基于滑移线理论的支盘成型过程对桩周土的扰动分析

为研究支盘桩桩型优化设计,就支盘桩单向成型过程对桩周土的扰动进行分析。以滑移线理论为基础,对挤土臂与土体作用进行力学化,建立单向挤压成型过程盘下土体的滑移线场模型,推导不同挤扩角盘下土体的应力场、速度场、土体极限荷载和塑性区分布,探讨成型过程对桩周土体的塑性区影响范围和盘下土体流动规律。结果表明,该模型计算的盘下土体影响深度与周明芳现场试验吻合较好,盘下土体的影响深度为0.47~0.49m;距离挤土臂越远,土体塑性流动速度越小,靠近挤土臂的土体挤密效果更好;土体极限荷载随挤扩过程的进行不断增大。研究结果具有工程应用价值,可为支盘桩桩型优化设计提供参考。     

嵌岩桩现场监测试验及负摩阻力优化计算研究

为了解决桩基负摩阻力所引起的桩体破坏、桩基不均匀沉降等工程问题,在桩周土体沉降及桩身应力应变现场监测试验的基础上,分析了嵌岩端承桩桩侧剪切变形与负摩阻力的关系,建立了嵌岩端承桩与周围土体剪切变形量的计算方法,对浅层位置处桩-土监测数据进行对比分析,同时考虑嵌岩端承桩周围土体竖向有效应力对剪切变形的影响,并对现有规范中嵌...     

石灰改良淤泥质黏土特性试验及应用研究

武汉市水系发达,存在大量软土,武汉市市政工程土方施工过程中通过采用石灰对开挖出的淤泥质黏土进行改良,在路基施工中取得了不错的效果。通过对拌和不同石灰含量的含水率最大淤泥质黏土改良土样进行土的承载比试验,得到8%的石灰含量淤泥质黏土改良土样的承载比能够满足规范要求,再探讨8%的石灰含量改良土样的物理力学变化规律,通过道路...     

输水管道顶管施工在不同因素下的地表沉降分析

为了解不同的土体参数、管径和埋深对顶管施工的影响,找出减小施工影响的控制措施,文章以山东省胶东地区某输水工程为例,采用ABAQUS软件中"生死"单元等功能对顶管施工引起的地表沉降进行了数值模拟,并与施工现场监测结果进行了对比分析,提出了角度控制、二次注浆、增大半径和土压平衡等控制措施,为今后类似输水工程管道顶管施工提供参考。     

考虑土体参数变异性的边坡稳定性分析

为探究土体参数变异性对边坡稳定性的影响,以驷马山分洪道切岭段膨胀土边坡为研究对象,利用GeoStudio软件建立边坡稳定性模型,Morgenstern-Price法求得边坡安全系数,并采用蒙特卡罗模拟法进行边坡可靠度分析。结果表明：当考虑土体参数变异性进行边坡稳定性可靠度分析时,随着干湿循环交替,膨胀土土体参数变异性越大,其可靠度指标降低越明显。本次试验表明：在实际边坡工程中,常规的极限平衡法判定边坡的稳定性是不全面的,需考虑土体参数变异性对边坡稳定性的影响。     

煤系地层岩石样品中黏土含量测定方法研究

针对煤系地层岩石样品中黏土含量测定方法的选择问题，采用焙烧+沉降分离法进行分析。首先采用焙烧法除去样品中的有机质并收集残留灰分，然后采用沉降分离法进一步对残留灰分进行黏土提纯，并以长庆油田苏里格区域石盒子组地层提取的煤岩样品黏土提纯过程为例，同时采用焙烧+沉降分离法与XRD分析法对其进行综合评判检验。结果表明：焙烧+沉降分离法与XRD分析法所得结果较为接近。因此，焙烧+沉淀分离法最大限度地实现了安全、高效、经济的测定煤系地层岩石中黏土矿物含量的目标，并取得了较为满意的结果。     

考虑表层植物生长特征的高标准农田渠坡生态改良试验研究

为研究农田灌渠表层植物生长特征对渠坡土体改良效果,开展了根系土的力学试验与渠坡可靠性仿真计算。试验得到,植物生长期1—3月与4—6月下根系土应变破坏特征各有差异;植物生长期愈大,则根系土应力愈高,但在生长期4月后,应力受生长期影响减弱,同时渠坡安全系数增幅也会减小。植物根径参数对根系土应变破坏特征影响较小。生长期不会改变渠坡断面含水量分布趋势。论文可为渠坡土体生态改良设计及渠坡稳定性分析提供参考。     

减少静压桩挤土效应的施工措施

静压桩施工对周围土体、建筑物及地下管线等设施会产生较大的影响。因此,在施工过程中为了避免给周边环境造成危害,会采取不同的施工措施来减弱沉桩产生的挤土效应。本文主要讨论了预钻孔取土打桩和设置防挤土槽对挤土效应的影响。     

不同载荷边界条件下的地铁站深基坑变形特性研究 ——以天津市某地铁车站为例

为更好地实现不同载荷边界条件下的基坑变形预测和控制,以天津市某地铁站深基坑为研究对象,研究超载、卸载条件下基坑变形特征.通过对现场监测数据的分析,推导基坑北侧和南侧的变形规律,并将分析结果与无超载、卸载条件的普通基坑进行水平位移、地表沉降、土体蠕变等方面的对比,最后,根据超载与卸载产生主动土压力对水平位移的影响,制定了...     

二次纤维水泥土力学特性研究

为弥补水泥土材料受压破坏后承载能力迅速衰减的缺陷,借鉴纤维改善水泥基材料性能的方法,以废纸降解获得二次纤维制成的二次纤维水泥土为研究对象,通过无侧限抗压试验分析其抗压强度、变形特征和破坏形态,提出考虑纤维掺量的应力-应变关系,探索水泥土改良新措施及废纸资源利用新途径。结果表明,1)养护28 d时,同样产生1.42%应变时,水泥土强度下降39%,而掺量为2%的二次纤维水泥土强度下降仅为27%,掺入2%二次纤维不仅可以提高水泥土强度0.42%,也可使水泥土达到峰值应力时产生的应变延后1.82%;2)纤维掺量存在一个阈值,当掺量高于阈值时纤维水泥土强度随养护时间的增加而降低,当掺量低于阈值时变化规律则相反;3)掺入2%和4%的二次纤维使水泥土由中部劈裂破坏转变为土体典型的剪切破坏,破坏时保留了水泥土产生裂纹较少,无明显挤压变形等优点。添加二次纤维可以在保持强度的同时减少水泥土工程缺陷,研究结果丰富了纤维水泥土理论,可为水泥土工程应用及基础研究提供参考。     

The associations of soil fertility and market access with household income: Evidence from rural Uganda

This study attempts to identify the major factors affecting farm and nonfarm income by using panel data of 894 rural households, interviewed in 2003 and 2005 in rural Uganda. We supplement the panel data with household-level soil fertility data and road distance data to the nearest urban center on three road types: tarmac, loose-surface, and dirt roads. The results suggest that soil fertility, measured by the soil organic matter (SOM) content, is positively associated with crop income but not with livestock and nonfarm income. We also find that the total road distance to the nearest urban center and the road quality have strong negative associations with the crop income.     

Soil management in relation to sustainable agriculture and ecosystem services

Requirements for research, practices and policies affecting soil management in relation to global food security are reviewed. Managing soil organic carbon (C) is central because soil organic matter influences numerous soil properties relevant to ecosystem functioning and crop growth. Even small changes in total C content can have disproportionately large impacts on key soil physical properties. Practices to encourage maintenance of soil C are important for ensuring sustainability of all soil functions. Soil is a major store of C within the biosphere – increases or decreases in this large stock can either mitigate or worsen climate change. Deforestation, conversion of grasslands to arable cropping and drainage of wetlands all cause emission of C; policies and international action to minimise these changes are urgently required. Sequestration of C in soil can contribute to climate change mitigation but the real impact of different options is often misunderstood. Some changes in management that are beneficial for soil C, increase emissions of nitrous oxide (a powerful greenhouse gas) thus cancelling the benefit. Research on soil physical processes and their interactions with roots can lead to improved and novel practices to improve crop access to water and nutrients. Increased understanding of root function has implications for selection and breeding of crops to maximise capture of water and nutrients. Roots are also a means of delivering natural plant-produced chemicals into soil with potentially beneficial impacts. These include biocontrol of soil-borne pests and diseases and inhibition of the nitrification process in soil (conversion of ammonium to nitrate) with possible benefits for improved nitrogen use efficiency and decreased nitrous oxide emission. The application of molecular methods to studies of soil organisms, and their interactions with roots, is providing new understanding of soil ecology and the basis for novel practical applications. Policy makers and those concerned with development of management approaches need to keep a watching brief on emerging possibilities from this fast-moving area of science. Nutrient management is a key challenge for global food production: there is an urgent need to increase nutrient availability to crops grown by smallholder farmers in developing countries. Many changes in practices including inter-cropping, inclusion of nitrogen-fixing crops, agroforestry and improved recycling have been clearly demonstrated to be beneficial: facilitating policies and practical strategies are needed to make these widely available, taking account of local economic and social conditions. In the longer term fertilizers will be essential for food security: policies and actions are needed to make these available and affordable to small farmers. In developed regions, and those developing rapidly such as China, strategies and policies to manage more precisely the necessarily large flows of nutrients in ways that minimise environmental damage are essential. A specific issue is to minimise emissions of nitrous oxide whilst ensuring sufficient nitrogen is available for adequate food production. Application of known strategies (through either regulation or education), technological developments, and continued research to improve understanding of basic processes will all play a part. Decreasing soil erosion is essential, both to maintain the soil resource and to minimise downstream damage such as sedimentation of rivers with adverse impacts on fisheries. Practical strategies are well known but often have financial implications for farmers. Examples of systems for paying one group of land users for ecosystem services affecting others exist in several parts of the world and serve as a model.     

姬塬油田储层伤害特征评价及解决对策探讨

基于姬塬油田延长组油井压裂投产的特点,从地质特征分析入手,对可能造成储层伤害的潜在风险进行了分析。研究结果表明:姬塬油田延长组储层粘土矿物含量高、孔喉细微是主要的潜在伤害因素,注入水与地层水、储层岩石不配伍形成有机垢加剧了储层伤害,压裂改造过程中压裂液滤失滞留、水不溶物、破胶残渣对储层造成不同程度的伤害。根据不同的伤害机理分析探讨了解决对策,现场应用了酸化、前置酸压裂、酸蚀多缝体积压裂及高黏强溶蚀酸转向酸化4种工艺,整体改造取得了较好的增油效果,对姬塬油田提高稳产水平和开发效益具有重要意义。     

磷酸二氢钾的制备工艺

综述了生产磷酸二氢钾的各种方法,认为以磷酸与氯化钾为原料和以碳酸氢铵、磷酸、氯化钾为原料生产磷酸二氢钾工艺路线在工业上是有利的。两条路线均存在原料易得、操作简便、收率≥95%、成本低、副产品能全部回收、无环境污染等优点。以磷酸与氯化钾为原料路线,需采用能避免腐蚀、利于氯化氢排出的专用设备,但所得KH2PO4质量好,w(KH2PO4)≥98%,w(Cl-)≤0 2%。以碳酸氢铵、磷酸、氯化钾为原料路线,设备简单、投资少,但KH2PO4质量分数一次性仅达92%～98%,质量较差。     

石家庄市不同梯度大气颗粒物碳组分特征分析

为了探讨石家庄市大气颗粒物中碳组分浓度水平与梯度变化,于2013年7月采集了石家庄市不同梯度大气颗粒物PM2.5,PM10和TSP样品,采用重量法测定颗粒物浓度,采用热光碳分析仪测定颗粒物中的EC(元素碳)和OC(有机碳)的浓度,并采用相关分析及丰度分析探讨石家庄市不同梯度碳气溶胶污染变化特征。结果表明:大气颗粒物中EC和OC主要存在于细颗粒物中,不同梯度颗粒物中OC和EC相关性较好,说明OC与EC的来源相似;不同梯度的ρ(OC)/ρ(EC)大部分超过2.0,表明石家庄市空气中存在一定的二次污染。从颗粒物中8个碳组分丰度初步判断石家庄市颗粒物中碳组分的主要来源是燃煤、汽车尾气及道路扬尘。     

加筋聚苯乙烯轻质膨胀土室内试验研究

为了研究加筋聚苯乙烯轻质膨胀土的膨胀与强度特性,将聚苯乙烯颗粒与膨胀土混合,聚丙烯纤维作为加筋材料,开展了包括密度、无荷膨胀率、膨胀力以及饱和快剪等室内试验。结果表明,聚苯乙烯颗粒和聚丙烯纤维的掺入可有效抑制膨胀土的膨胀特性,表现为无荷膨胀率与膨胀力的显著减小;聚苯乙烯颗粒主要起到体积置换作用,土样密度以及膨胀力随聚苯乙烯颗粒掺量增加线性减小;随着聚苯乙烯颗粒的增加,混合土内摩擦角持续增大,黏聚力先增加后降低;随着纤维掺量的增加,混合土的黏聚力得到有效增长。因此,加筋聚苯乙烯轻质土在改良膨胀土方面具有良好的应用价值。     

用畜禽粪便生产无公害有机肥质量控制的研究

以鸡粪为畜禽粪便的代表性原料与辅料混合,控制m(C)∶m(N)=(25～35)∶1,含水率为55%～60%,添加菌剂的质量分数为0.3%～0.5%。采用2阶段有机肥发酵工艺:前发酵阶段为好氧发酵,50～60℃维持7～8d;后发酵阶段为厌氧发酵,25～45℃维持15～20d。转变成的无公害优质有机肥,达到了《粪便无害化卫生标准》(GB7959-87)。     

玻璃球负载纳米级SO_4~(2-)/TiO_2固体超强酸的研究

制备了玻璃球负载纳米级SO42-/TiO2固体超强酸,对其催化活性、重复使用效果、失活原因及再生方法进行了研究。该催化剂对乙酸和丁醇的酯化反应在重复使用9次后,反应3 h乙酸的转化率由初次的99.3％变为84.9％,经再生处理,再重复使用6次反应3 h乙酸的转化率由初次的98.0％变为78.3％。催化剂失活原因为活性中心被有机物覆盖以及SO42-的流失。催化产物的气相色谱说明该催化剂选择性好,无副产物生成。     

2-丙烯酰胺基-2-甲基丙磺酸接枝改性瓜尔胶的制备与性能研究

为改善瓜尔胶与其他组分的相容性及耐盐性,以可生物降解的瓜尔胶为原料,过硫酸钾和亚硫酸钠为氧化还原引发体系,将2-丙烯酰胺基-2-甲基丙磺酸(AMPS)接枝到瓜尔胶分子上。研究AMPS用量、引发剂用量、引发剂滴加时间、反应时间、反应温度、分散剂与瓜尔胶的质量比(浴比)、分散剂中乙醇质量分数等因素对接枝反应的影响,确定较佳反应条件。制得的磺酸基瓜尔胶衍生物胶液稳定,黏度较高,在质量分数为2%的KCl盐水溶液中黏度下降很小,具有良好的耐盐性。将其按一定比例与牙膏成分进行混合,其与牙膏组分的相容性好,膏体稳定且改善了脱尾现象,满足作为水性膏体黏结剂的要求。