大连港大窑湾吹填区软基的堆载预压处理研究

结合大连港大窑湾吹填区软土地基处理具体工程,通过现场试验与监测比较详细地介绍了堆载预压方法中关于分级堆载设计、施工及监测等各方面的技术问题。通过对监测结果的综合分析,探讨了堆载预压处理过程中地表沉降、深层沉降等关键参数的变化规律及堆载级数、堆载高度与固结时间等参数之间的依赖关系,为吹填造陆地区软基处理提供了经验和依据。     

邯郸击实膨胀土的微结构与含水量关系研究

定性分析了邯郸击实膨胀土在不同含水量下的结构形式,发现邯郸击实膨胀土的微结构在含水量较低时,表现为集粒结构;在含水量较高时,定向性增强,趋于紊流结构。利用Matlab数字图形处理工具,结合像素的概念,通过编程计算不同含水量下土的颗粒分布分维,发现含水量较低时,分维值较大,颗粒集团化低;含水量较高时,分维值较小,颗粒集团化高。     

Transformation kinetics and potential availability of specifically-sorbed phosphate in soils

The improvement of P management in agriculture and environment requires a good understanding of residual effect of applied P in soils. The specific adsorption of P on variable charge minerals has been considered as the major mechanism that leads to a very low utilization of P fertilizer by crops within a growing season in Chinese red soils. Soil incubation and isotope tracing analysis were carried out to examine the transformation kinetics and potential availability of added specifically sorbed ³²P in two pH contrasting light textured soils. The ³²P recovered by 0.5 M NaHCO₃ extraction and microbial biomass-P measurement from the added specifically sorbed ³²P in the soils was well described by a first-order reaction and a Langmuir-type kinetic model, with correlation coefficients (R) being, on average, 0.938 and 0.959, respectively. The half-life (t_1/2, from the first-order model) of the four tested mineral-P complexes ranged from 29 to 47 d in the acid sandy soil and 33 to 105 d in the neutral silty soil. Goethite-P was the most stable among the four tested mineral-P complexes. The potential availability of the mineral complex P (q _m , in percent of total ³²P added) obtained from the Langmuir equation ranged from 43.7 to 90.9% for the four mineral-P complexes, and decreased in the order: Al oxide-P (90.9%) > montmorillonite-P (86.2%) > kaolinite-P (77.5%) > goethite-P (60.2%) in the acid sandy soil, whereas the order was Al oxide-P (89.3%) > kaolinite-P (86.2%) > montmorillonite-P (82.6%) > goethite-P (43.7%) in the neutral silty soil. Based on the release rate and potential availability, kaolinite-P and Al oxide-P could be important sources for residual effect of applied P in variable-charge soils. The goethite-P has the lowest release rate and potential availability among the mineral-P complexes, implying that iron oxides may be the most important variable-charge mineral responsible for P fixation in the Chinese red soils.     

气干性不饱和聚酯树脂的合成及其性能

讨论了阻聚剂(对苯二酚)的用量对不饱和聚酯树脂凝胶时间及贮存期的影响;同时使用了烯丙基醚基团(CH2=CH—CH2—O—)作为气干性基团,对传统不饱和聚酯树脂进行改性,讨论了烯丙基醚用量对不饱和聚酯树脂气干性的影响。实验结果表明,最佳对苯二酚用量为0 016%,烯丙基醚用量>20%。     

低应变条件下桩土相互作用的阻尼系数

低应变条件下桩土相互作用的阻尼系数是基桩缺陷量化分析的一个关键参数。为通过试验直接确定桩土相互作用的阻尼系数,建立桩土相互作用的定解方程,分析两端自由的摩擦桩在不同阻尼系数时的桩顶速度波时程变化,推导桩顶速度响应幅值比与阻尼系数之间的关系。在此基础上,选用6种桩侧土,针对土层饱和前、后两种状态,进行不同上覆有效应力作用下土层与桩相互作用的模型试验,确定桩侧土阻尼系数,研究阻尼系数随土性、土层上覆有效应力的变化。试验结果表明,6种桩侧土阻尼系数均随土层上覆有效应力增加而呈指数关系增加,不同土类指数关系中的系数不同;与饱和前的砂土与粉土阻尼系数相比,相同土层上覆有效应力下饱和后砂土与粉土的阻尼系数降低25%～60%;当土层上覆有效应力从85 kPa增加到850 kPa时,饱和粉质黏土的阻尼系数从250 s-1增加至890 s-1;当土层上覆有效应力从20 kPa增加到150 kPa时,饱和软黏土的阻尼系数从330 s-1增加至420 s-1。最后,将试验得到的阻尼系数与其他方法确定的阻尼系数进行比较,进一步说明通过试验测定桩土相互作用阻尼系数的必要性。     

基于分数阶黏弹性地基模型的群桩时效行为研究

基于有限单元法,将群桩划分为有限个2节点单元,从而构建了竖向受荷群桩的有限元求解方程;为了模拟饱和软黏土的流变特性,通过Laplace变换,推导了分数阶导数Merchant模型中的应力–应变关系;引入弹性-黏弹性对应原理,得到横观各向同性分数阶黏弹性饱和软土地基的边界元解答;考虑桩-土界面处的位移协调,将群桩有限元求解...     

Particle loss: An initial investigation into size effects and stress-dilatancy

Drained triaxial tests have been performed to explore the effect of particle loss on shearing behaviour and critical states in granular mixtures. The mixtures comprise Leighton Buzzard sand (d₅₀ = 0.8 mm), to which was added 15% by mass of salt particles of different nominal sizes: 0.063 mm, 0.25 mm and 0.5 mm. Shearing behaviours before and after particle loss (by dissolution) were compared. A good fit is observed between the test data and a stress-dilatancy relationship for the post-dissolution tests, highlighting the ability of the stress-dilatancy analysis as a means to interpret the effects of particle loss on shearing. It was noted that critical state strength parameter M is determined by the post-dissolution grading regardless of size of removed particle. However, the duration of contractant volumetric strain increased with the larger removed particles (0.25 mm & 0.5 mm) even when initial specific volumes were virtually identical. It is suggested that a loose volumetric state is reached if the sand particle network is initially disrupted by the amount and/or size of salt particles, which following dissolution results in structural or fabric phenomena that are not reflected in scalar volumetric measures such as specific volume.     

深厚软土地基增强型管桩受力性状试验研究

增强型管桩采用离心旋转法制作,并经高温蒸养,在制桩时预埋应变计难以实现,本文研制了一种桩身埋设混凝土应变计的新方法,成功解决了这一难题。通过静载试验研究了深厚软土地基中增强型管桩的荷载传递规律及桩侧摩阻力和桩端阻力的发挥性状,探讨了增强型管桩桩身肋的荷载分担情况。试验结果表明,在竖向荷载作用下,增强型管桩桩身上部的肋比下部的肋先发挥作用,肋对桩侧摩阻力的发挥起到了明显地加强作用。     

焦化厂土壤中PAHs的累积、垂向分布特征及来源分析

引言多环芳烃(polycyclic aromatic hydrocarbons,PAHs)在环境中普遍存在,由于具有强烈的诱变、致癌和致畸作用而受到越来越多的关注。以煤为主要原料的焦化行业,是环境中人类活动产生PAHs的主要来源之一,其各个生产车间内化石燃料的不完全燃烧及焦油、煤气等化工产品的加工过程都可能导致PAHs的排放。土壤是PAHs累积和迁移的重要介质,环境中的PAHs可由大气     

Zinc diffusion and extractability as affected by zinc carrier and soil chemical properties

This work was carried out to evaluate the effect of soil chemical properties, Zn carrier and time elapsed after fertilizer application on the diffusion and extractability of Zn. A soil block technique was used to study zinc diffusion and DTPA extractability from ZnEDTA and ZnSO₄ fertilizers in three soils that varied in texture, CaCO₃ content, organic matter content, and pH using Zn⁶⁵ tracer. ZnEDTA diffused readily in all soils, moving 20–25 mm from the fertilizer layer after three days. The rate of Zn diffusion and the extractability of Zn, however, varied among the soils and were lowest in Baha soil with the highest clay content, organic matter, and CEC despite its lower pH. The high pH and CaCO₃ content in Dirab soil did not restrict the diffusion or reduce the extractability of ZnEDTA in this soil. On the other hand, the diffusion of Zn from ZnSO₄ fertilizer was largely restricted in all soils and was confined to 5 mm from the fertilizer layer after 13 d. The extractability of ZnSO₄ fertilizer was largely affected by soil pH and CaCO₃ content and was lowest in Dirab calcareous soil. Organic matter amendment at 5% (as alfalfa) considerably reduced the diffusion and the extractability of ZnSO₄ in both Dirab calcareous and Bakyria noncalcareous soils. The application of 1% (w/w) elemental S reduced soil pH and increased Zn diffusion from ZnSO₄ fertilizer in Bakyria soil but had slight effect on Dirab calcareous soil.