三峡水库变动回水区泥沙淤积状况及治理

本文根据《长江三峡泥沙和航运问题的研究成果汇编》等资料，分析了变动回水区航道及港口状况，提出了整治与改善建议等应急对策。     

山区公路路侧安全性研究及对策

山区公路的路侧事故率较高,这与山区公路中缺乏防护设施的保护有关。为改善山区公路安全性能,降低车辆冲出路外的路侧事故,对公路路侧安全性设计原则进行研究,从而提高路侧安全设计水平。针对山区公路特有的特点,提出在山区公路中应加强路侧护栏的设置,路侧护栏作为公路上基本的交通安全设施,能减轻事故的严重度。     

Granular effect of fly ash repairs damage of recycled coarse aggregate

Repairing effect of fly ash (FA) on damage of recycled coarse aggregate was evaluated by characteristics of pores and cracks in the vicinity of interracial transition zone (ITZ). The interracial structure between the virgin aggregate and the attached old mortar was investigated and compared with ITZ of recycled aggregate concrete in the presence of FA or ultra-fine FA(UFA) by means of scanning electron microscope (SEM). Diam- eter and plumpness frequency distribution of pores as well as width of the old ITZ, length of contacting points and cracks density were analyzed. The SEM results reveal that the diameter of pores is decreases significantly but pores plumpness increases. A decreased ITZ width and cracks density as well as an increased bonding zone length can also been observed, which indicates that FA or UFA repairs damage of recycled coarse aggregate due to its granular effect.     

The slippery slope of lot consolidation in the Santa Monica Mountains: A program assessment

Abstract

The authors present an assessment of the Coastal Conservancy's efforts to consolidate small, substandard lots in the Santa Monica Mountains. Emphasis is placed on the ‘ ‘lessons learned’ ‘ by the Conservancy in its project experience as those lessons may be applicable to related efforts elsewhere. Finally, alternative means of lot consolidation are suggested. This assessment should be of relevance to other programs nationwide to address the problem of antiquated subdivisions.     

分层加筋技术与冻土路基裂缝防治

裂缝是多年冻土路基的特殊性问题之一。为抑制路堤裂缝的产生和发展,在填土中分层敷设土工格栅,利用土工格栅良好的抗拉性能,提高路堤土体强度,增强路堤整体稳定性,减少路基土体自中心向两侧的水平位移,试验和工程实践证明是一种行之有效的工程措施。     

多年冻土区灌注桩的人工冷却试验研究

多年冻土区灌注桩修筑过程中，混凝土携带的热量和水化热会对周围冻土产生强烈的热扰动，由于基础在回冻前承载力非常小，因此桩基的快速回冻已成为该地区基础设施建设中备受关注的问题。为解决该问题，创新性地提出人工冷却法在多年冻土区灌注桩中的应用，以实现基础的快速降温和回冻，并在青藏高原北麓河进行现场人工冷却灌注桩试验。试验结果表明：人工冷却降温效果显著，试验进行到第2天，基础周围土体温度已经降至天然场温度以下；随着冷却试验的继续进行，基础和周围土体的温度会进一步降低；人工冷却有效降低了土体温度，并增加了桩基周围土体的冷储量，冷却试验结束后的第7个月试验桩的平均界面温度为-0.6℃，无冷却措施桩对应的平均界面温度为-0.37℃。承载力计算结果表明：人工冷却可以快速、大幅提高桩基的承载力，通过该措施的应用，试验桩的承载力可提高至2 231 kN，而无冷却措施桩对应时刻的承载力仅为549 kN；该措施有效缩短了冻土区灌注桩施工的后续等待时间，经过人工冷却的桩基承载力很高，冷却结束后即可进行上部荷载的施工。人工冷却可作为冻土地区桩基快速施工中的一种重要方法和有效途径，其不仅能够解决灌注桩对冻土产生热扰动这一难题，还能够有效缩短工程的建设周期，具有很高的工程应用价值。     

The annual cycle of nanoflagellates in the Central Cantabrian Sea (Bay of Biscay)

The annual cycle of nanoflagellates (NF) including autotrophic (ANF), heterotrophic (HNF) and mixotropic (MNF) flagellates carried out in a temperate sea (Central Cantabrian Sea, southern Bay of Biscay) is presented. Three stations with characteristics ranging from coastal to oceanic conditions were analysed in order to compare NF response to this gradient. Samples were monthly collected at each station at three different depths between February 2002 and December 2002. CTD profiles were also taken at each station. NF were grouped according to their trophic status into ANF, HNF and MNF. Abundance and biomass were determined for each group. The annual cycle showed a general pattern consisting in a maximum in July with secondary maxima in March and October and minimum values in May. ANF were the most important fraction, making a major contribution (nearly 75%) to total NF biomass in all stations. HNF represented over 20% along the cycle, except for a peak in spring found in every station. MNF reached less than 5%, showing low seasonability. Small flagellates (2–5 µm) dominated throughout the cycle. Microplankton community was also analysed in terms of abundance and biomass. A significant positive correlation (r² = 0.49) was obtained between 2–5 µm NF and 10–20 µm HNF–MNF biomasses, suggesting a possible trophic relationship between these groups which should be cautiously taken. No significant relationships were found between microplankton and NF or between nutrients and ANF, indicating that the regulation of NF numbers is complex and probably implicates other groups. In addition to this, the unexpected 2002 Chl a concentration pattern and the misplacing of upwelling events render necessary to perform additional studies to fully understand the precise behaviour of NF in the Cantabrian Sea. To the best of our knowledge, this is the first study of a NF cycle in a temperate sea that considers all functional groups.     

台电碧海水力发电头水隧道设计及施工实例

碧海水力发电工程头水隧道为台湾东部变质岩地层内施作之水力发电用隧道,位处花莲和平溪右岸之崇山峻岭中,地形条件恶劣,工程初期施工道路尚未全线贯通阶段,采中重型直升机吊挂运补施工用物资、人员及机具,争取工期。工程头水隧道因通水断面净内径仅2.7 m,长度约6.5 km,设计及施工条件严苛,台电公司为缩短工期,选择TBM工法,惟第一承揽厂商遭遇涌水带后,TBM夹埋未能脱困,终至解约。后由另一厂商接手,采传统钻炸工法,顺利拆解TBM并如期贯通,配合排水钢管,导引涌水,并设计自走式钢模,内衬砌浇置速度创台湾水力隧道之新纪录。     

河流峡谷地段地质选线方案研究

研究目的：河流峡谷地段，不良地质极为发育，规模大，又为地下水的排泄区，发育区域性暗河；线路设计同时受技术标准、投资影响；控制选线的因素极为复杂。本文以渝怀线乌江峡谷地质选线研究为例，对经受施工、运营、汶川地震检验，证明合理的地质选线的经验、成果进行研究、归纳、总结，指导类似河流峡谷地段铁路勘察设计工作。研究结论：先期进行河流左、右岸地质选线；峡谷段不良地质极发育，线路方案受地质条件控制，有条件时，线路内移避开沿岸不良地质；线路绕避不良地质困难或代价极高时，只要地质探明，工程措施到位，线路完全可以通过不良地质；根据岩溶发育规律及暗河标高，宏观指导选线，线路最好尽量选择通过岩溶发育安全带。     

百丈隧道穿越流塑状富水破碎带施工措施及其安全性评价

百丈隧道左洞ZK152+433~ZK152+463段穿越流塑状富水破碎带施工时反复出现变形侵限、塌方等情况,给工程施工带来前所未有的挑战。文章详细阐述了施工过程中采取的各种处治措施,总结了不同处治方案和效果,并采用数值分析方法对隧道结构安全性进行了分析。结果表明:(1)对于流塑状富水破碎带,加密超前支护是防止开挖时围岩出现较大变形或者坍塌的最有效措施。百丈隧道流塑状富水破碎带最终采用了每榀钢架(钢架间距50 cm)都打设一环3.5 m长?51自进式锚杆的超前支护方式,即每个断面都有7层超前支护,最终有效控制了开挖后围岩变形,避免衬砌侵限与塌方;(2)对于流塑状富水破碎带,加固围岩尤其是边墙与基底处围岩非常重要,可有效减少开挖过程中衬砌的整体式下沉。采用抛石挤淤+注浆的方式进行边墙与基底围岩加固,其效果比采用单纯注浆方式好得多;(3)对于外部荷载较明确的隧道,采用计算分析结合工程经验的方式确定衬砌支护参数,既能保证隧道结构安全,又使其经济合理;(4)在双车道隧道施工中,采用三台阶法施工,应尽量缩短台阶长度,使初期支护及时封闭成环,从而可以较好地控制围岩变形。