武汉下善湖湖堤软土堤基工程地质特性分析

拟建下善湖湖堤位于堆积平原区和剥蚀丘陵区之间过渡地带,湖堤范围内广泛分布淤泥质黏土层,属于软土堤基。通过工程地质测绘、钻探、原位测试及室内试验等工作,划分了堤基地质结构类型,对堤基工程地质条件进行了分类,查明了软土堤基的物理力学性质和工程地质特性,分析了软土的空间分布特征和物理力学性质。研究表明:该软土堤基具有含水率高、孔隙比大、中高压缩性、中高灵敏性、透水性微弱、强度低等特点,堤基主要存在软基沉降变形、抗滑稳定等工程地质问题。针对工程地质问题提出了相应的地基处理措施。     

堤基工程软基硬壳层的作用分析和利用

根据堤基工程的软基硬壳层情况，分析软土地基硬壳层的划分标准和不同成因的硬壳层的工程性质，讨论软基硬壳层的作用机理、软基硬壳层对堤基沉降和稳定的作用以及软基硬壳层作用在土压力上的反映．对软土地基上的堤基工程设计、施工和管理具有指导意义。     

围海工程滩涂的软土特性与筑堤技术

本文是群众性筑堤经验与科学实验的综合性总结。简述了我国东南沿海滩涂软土的分布与特性,及各种海堤断面型式与软基筑堤技术的发展;并介绍在天然强度下软基的稳定计算方法,及对极软弱地基采用排水固结法加固以提高堤基的承载力。     

海堤软土地基主要处理方法的技术经济分析

浙江沿海多为高含水量、孔隙比大、透水性差的淤泥及淤泥质黏土软土地基,地基承载力及抗剪强度低、地质条件差。软土地基处理是海堤的技术难题,对海堤的稳定安全性至关重要;目前,软基处理方法主要有塑料排水插板法和爆炸置换法。各方法互有利弊,具体工程设计时应进行多方案技术经济分析,择优确定软基处理方案。     

软土堤基固结沉降预测的数值仿真分析

针对青草沙水库软土堤基固结沉降需持续若干年,为了研究分析软土堤基的固结沉降值及其规律性,本文利用大型通用有限元软件ADINA精细地建立了2-D Solid平面应变单元,含地下水的土体变形计算必须考虑孔隙水压力与土体变形之间的关系。依托青草沙水库工程,软土堤基采用多孔介质的岩土本构模型(土体骨架属性和孔隙水属性),岩土体双向排水,随着孔隙水压力不断消散,堤基不断固结沉降,根据数值仿真计算来研究分析堤基固结沉降的过程及规律,同时利用现场水库堤基的沉降监测数据作对比分析,能够准确地预测堤基沉降达到稳定时所需固结时间及最终固结沉降值。     

滨海城市建设软基处理施工工艺

随着我国滨海区域向外的不断扩展的城市化建设，不可避免的涉及到沿海滩地、江河出海口河滩区域，这些区域大多分布着大量近代沉积的软土地层或较厚的淤泥和淤泥质黏土层，这类软土及淤泥质黏土层的特性主要体现为孔隙比较大、含水率较高、渗透性较差、强度及承载力低等，且具有明显的流变性和一定的结构性。结合温州市龙湾区浅滩软基处理工程实践经验，通过对堆载预压法、真空预压法、水泥搅拌桩复合地基法、电渗降水强夯法等几种常用的软基处理施工工艺在工期、工程费用、施工难易程度、适用范围及处理效果等方面对比研究。     

浙东沿海围垦工程软基处理及海堤结构的方案优选

淤泥地基属高含水量、高压缩性、高灵敏度、低强度的软弱地基,其地基承载力及抗剪强度低,工程地质条件差。软土地基处理是海堤的主要技术难题,对海堤的稳定安全性至关重要,地基处理费用高。目前,软基处理方式主要有PVC塑料排水板与爆炸置换法、桩基法等,上部海堤结构主要有土石实体结构、钢筋混凝土空箱结构等。各方案互有利弊,具体工程设计宜进行多方案技术经济比较,择优确定软基处理及结构方案。     

深圳市海上田园风光下游段整治软土勘察浅析

软土泛指淤泥及淤泥质土,是静水或非常缓慢的流水环境中沉积,并经生物化学作用形成的饱和软粘性土,其具有含水量高、孔隙比大、压缩性高、抗剪强度低、透水性弱、排水固结不畅、灵敏度高等特点。我国软土主要分布在东海、黄海、渤海、南海等沿海地区,内陆平原及一些洼地也有分布。软土地区勘察及基础处理一直是工程建设中的技术难题,笔者有幸参加了深圳市海上田园风光下游段整治工程地质勘察工作,就软土地基浅谈自己的一点心得。     

水工建筑物的地基分类及特点

正一、水工建筑物的地基分类水工建筑物的地基分为两大类型,即岩基和软基。1.岩基是由岩石构成的地基,又称硬基。2.软基是由淤泥、壤土、砂、砂砾石、砂卵石等构成的地基。又可细分为砂砾石地基、软土地基。(1)砂砾石地基是由砂砾石、砂卵石等构成的地基,它的空隙大,孔隙率高,因而渗透性强。(2)软土地基是由淤泥、壤土、粉细砂等细微粒子的土质构成的地基。这种地基具有孔隙率大、压缩性大、含水量大、渗透系数小、水分不易排出、承载能力差     

换土垫层法处理软弱基础的探讨

1 软弱地基 软弱地基是一种不良地基,按形成因素可分为人工素填土软基,海相、河相和湖相沉积的淤泥质软基;山洪冲积的夹碎石的粘性土软基。由于这些复杂的因素造成了软基具有强度低、压缩性高、透水性低的不良特性,在软基上建造的构筑物,由于基础的承载力和变形不能满足设计要求,需要进行地基处理以达到提高软基强度、降低软土的压缩性、减少基础不均匀沉降的目的。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。