沉入钢管干取土灌注桩

沉入钢管干取土灌注桩是适用于软土地区的新型高效优质桩。本文介绍了干取土灌注桩的施工设备、工艺及其设计与质量检测方法，并简单分析了该桩型的技术经济特点。该桩型具有无泥浆污染、对邻周环境影响小、承载力大、质量可靠和工程造价低等优点，具有较大推广应用价值。     

Effect of infiltration on the performance of an unsaturated geotextile-reinforced soil wall

A full-scale geotextile-reinforced soil wall was built in order to assess the characteristics of water infiltration and its effect on the structure performance. Nonwoven geotextiles were selected as inclusions in order to provide not only reinforcement, but also internal drainage to the fine-grained soil used as backfill material. The structure was built in a laboratory setting, which facilitated implementation of a thorough instrumentation plan to measure volumetric water content changes of soil, suction, facing displacements and reinforcement strains. An irrigation system was used to simulate controlled rainfall events. The monitoring program allowed the evaluation of the advancement of infiltration and internal geosynthetic drainage. Evaluation of the effect of the hydraulic response on the overall performance of the structure included assessment of the development of capillary breaks at soil-geotextiles interfaces. Capillary breaks resulted in water storage above the geotextile reinforcements and led to retardation of the infiltration front in comparison to the infiltration that would occur without the presence of permeable reinforcements. After breakthrough, water was also found to migrate along the geotextiles, suggesting that the reinforcement layers ultimately provided in-plane drainage capacity. While generation of positive pore water pressures was not evidenced during the tests, the advancing infiltration front was found to affect the performance of the wall. Specifically, infiltration led to increasing reinforcement strains and facing displacements, as well as to the progressive loss of suction. While the accumulation of water due to the temporary capillary break also resulted in an increased backfill unit weight, its effect on deformation of the wall was not possible to be captured but it is intrinsic on the overall behavior observed in this study. Correlations between reinforcement strains/face displacement and the average of suction in the backfill soil, as measured by tensiometers in different locations within the backfill mass, point to the relevance of the suction as a representative indicator of the deformability of the geotextile-reinforced wall subjected to water infiltration. Reinforcement strains and face displacements were found to reduce more significantly with reduction of suction until a certain value of suction from which the rate of decreasing declines.     

软弱土层基坑水泥搅拌桩止水帷幕失效分析

以广州市某基坑工程止水帷幕失效为背景,对软弱土层地质条件下的城市深基坑水泥搅拌桩止水帷幕失效原因进行了分析。土体中的有机质含量、固化剂的比例及桩体有效入土深度等因素对水泥搅拌桩的成桩质量和止水效果有较大影响。城市深基坑通常施工场地比较狭窄,基坑的支护结构、电梯井基坑、降水及其他工程对水泥搅拌桩的施工质量有时也会产生较大影响,因此应做好相应的设计和施工管理工作。     

Soil productivity analysis based on a fuzzy logic system

BACKGROUND: Maintaining soil productivity is essential if agriculture production systems are to be sustainable. However, there is a paucity of tools for measurement for the purpose of understanding changes in soil productivity. Fuzzy logic‐based analysis offers this possibility. It is a new method on the evaluation of soil productivity in Turkey and even in the world. RESULTS: Values for pH, salinity, carbonate and organic matter were entered into the system as input variables so as to obtain soil productivity as the output. After the membership functions related to input and output were determined, rules were created. Then, the fuzzy logic system was applied separately to pH, salinity, lime and organic matter values of different soil types present in the Kocaeli region with the aim of obtaining corresponding fuzzy values. Thus, soil productivity profiles of the region were deciphered. CONCLUSION: Organic matter levels in the study field remained below 30 g kg^?1 and varied between 22 and 28 g kg^?1. Productivity values were obtained as a percentage and varied between 16.9% and 18.1%. The lime content of the study soils varied in the range of 33–88 g kg^?1. Average totals for salt values of the field changed between 0.58 and 0.77 g kg^?1. Copyright © 2010 Society of Chemical Industry     

某桁架结构与地基基础共同作用分析

针对某些情况下，地基变形会对结构内力产生较大影响的情况，通过对某一桁架结构的分析表明，在地基变形较不均匀时，忽略结构与地基基础共同作用会导致结构不安全，以指导相关设计人员注意这一影响。     

浅谈骨架密实型水稳基层特性及配合比设计

通过从材料本身抗裂性能评价研究入手,阐述了骨架密实结构配合比设计方法,以具体配合比在工程实践中的应用为基础,提出工艺过程控制以减少裂缝的发生,以期促进骨架密实型水稳基层的推广应用。     

软基桩侧负摩阻力弹塑性分析及几个关键问题

文中基于桩土共同作用机理,考虑桩土体接触面效应,建立了软土地基桩侧表面负摩阻力三维弹塑性有限元分析模型。在此基础上,重点模拟分析了某典型软土地基土体特性、桩土接触面参数、土体结构性及堆载等因素对负摩阻力的影响规律。最后,对未来关于负摩阻力研究仍亟需解决的几个关键问题等进行了初步探讨。研究成果和分析思路可为类似条件下桩侧负摩阻力的计算和施工提供有益的参考。     

Direct displacement-based assessment with nonlinear soil–structure interaction for multi-span reinforced concrete bridges

A practical and readily implementable seismic assessment procedure for multi-span reinforced concrete bridges is introduced in this paper. The procedure is based on an existing direct displacement-based assessment (DDBA) approach, and accounts for nonlinear dynamic soil–structure interaction (NLSSI) effects. Several simplified bridge structures lying on shallow foundations have been used as application examples. The validation has been done by comparing DDBA+NLSSI with the results of finite-element nonlinear time-history simulations by means of incremental dynamic analysis. Moreover, the influence of NLSSI on the assessment procedure has been evaluated by considering the same bridges with fixed base and with NLSSI effects. In spite of its simplicity that presently prevents its use for complex bridge structures, the proposed procedure is found to provide fast and reliable results, useful to give a first-level screening on a large set of bridges for highlighting the most critical situations, as well as to carry out fast parametric analyses to produce fragility curves in the framework of performance-based vulnerability/risk assessment.     

Sorption of Pyrene to Two Estonian Soils

Two typical Estonian soils, Brown pseudopodzolic and Rendzina, were used for sorption studies with pyrene. The soil samples were subjected to a variety of chemical and physical tests. The specific surface area reached 3.05 m² g^?1 for Rendzina, and 0.87 m² g^?1 for Brown pseudopodzolic soil. The Rendzina type of soil was characterized also by a high organic matter content (22.9%) compared with the Brown pseudopodzolic soil (6.64%). A batch technique was used to perform all adsorption studies. K_oc values 2.7 × 10⁴ mg g^?1 for Rendzina and 4.5 × 10⁴ mg g^?1 for Brown pseudopodzolic were obtained. The results suggets that pyrene sorption behaviour could be in some instances mainly influenced by the composition of organic compounds in the soil, not so much by the overall organic matter content. Also the mineral part of the soil can have a impact to pyrene sorption through Ca-binded humic substances.     

KINETICS OF PAHS LOSSES AND RELATIONSHIPS BETWEEN PAHS PROPERTIES AND PROPERTIES OF SOIL IN SEWAGE SLUDGE-AMENDED SOIL

Abstract

The properties of soil determine the activity of its microflora which is responsible for the degradation of polycyclic aromatic hydrocarbons (PAHs). Moreover, soil properties influence the strength of the interactions between the PAHs and individual soil components. The introduction of sewage sludge into the soil changes these properties which, in turn, changes environmental conditions. In the present studies, relationships between the PAH content and changes in selected soil properties (pH, CEC, TEB, BS, N _t ) have been evaluated. The present experiment was carried out in two blocks of experimental plots divided according to the type of plants grown. In the first block, the following field plants were grown in specific sequence, (maize, spring barley, winter rape, potatoes and cereal mixture) while in the other block a perennial, i.e. willow, was grown. Plant cultivation was carried out for 54 months, whereas the cultivation of the willow was conducted over 42 months. Each block consisted of 6 plots with a surface area of 15 m² into which sewage sludge had been introduced in the following doses: soil without fertilization – control, sludge 30, 75, 150, 300, 600 t/ha. Both the disappearance rate and the scope of the individual polycyclic aromatic hydrocarbons as determined by their respective half-lives showed that losses of these compounds depended on the sewage sludge properties (among other things, the pollutant content) as well as the sludge dose and the type of area used. The correlation coefficients determined depended on the sludge dose and the experimental variant. The highest frequency of their occurrence was found in the case of the total sum of nitrogen and cation exchange capacity for the highest sludge doses (in the experimental with willow).