上覆富水砂层地铁隧道掌子面变形特征数值试验研究∗

为研究地铁隧道在上覆富水砂层下的变形特征，以典型上覆富水砂层隧道—青岛地铁 2 号线啤—苗区间为工程研究背景，采用 FLAC 3D 数值模拟软件对不同富水砂层厚度与隔水层厚度工况下隧道掌子面位移、塑性区变化特征进行了研究分析。研究结果表明：隔水层厚度是影响掌子面是否发生涌水涌砂的主控因素，在开挖过程中应时刻注意富水砂层距离隧道顶板的安全距离，临界隔水层的厚度为 3 m。同时，当隔水层厚度越大、富水砂层厚度越小时，掌子面变形就会越小。以临界工况为研究对象，通过分析开挖过程中隧道拱顶—拱腰—掌子面应力和位移变形规律，引入了位移释放系数和应力释放率两参数来揭示围岩与掌子面在隧道开挖过程中的影响关系。通过进一步拟合掌子面失稳破坏预测方程，得到了掌子面变形释放率拐点先于同一断面围岩径向变形且发生在开挖到目标断面之前的重要结论，因此在实际隧道开挖过程中应将掌子面的变形作为首选敏感监测指标。研究结果可为该不良地质条件下隧道掌子面稳定性和预加固时机选择提供一定的理论指导。     

Linking land degradation and restoration to ecosystem services balance by identifying landscape drivers: insights from the globally largest loess deposit area

Environmental Science and Pollution Research - Land degradation is one of the most serious environmental challenges that profoundly affects ecosystem services (ESs), which further threaten...     

Open Pore Morphology Evolution in Poly(butylene succinate)/Chitin Nanocrystal Nanocomposite Foams

Journal of Polymers and the Environment - In recent decades, biodegradable polymeric open-porous foams have been engaging increasing interests owing to their biodegradability, porosity and...     

Association of selenium,arsenic, and other trace elements in drinking water and urine in residents of the plateau region in China

Environmental Science and Pollution Research - Drinking water is considered to be an important exposure pathway for humans to ingest trace elements; human urine samples are widely accepted...     

Effect of Plasticizer Content on the Structure and Properties of SPI/MA-g-PBAT Blend Films

Journal of Polymers and the Environment - Soy protein isolate (SPI) has the advantages of low cost, easy processing, stable performance and so on. However, the processing temperature of SPI is...     

A qualitative systematic review of governance principles for mangrove conservation

Management of mangrove ecosystems is complex, given that mangroves are both terrestrial and marine, often cross regional or national boundaries, and are valued by local stakeholders in different ways than they are valued on national and international scales. Thus, mangrove governance has had varying levels of success, analyzed through concepts such as principles of good governance and procedural justice in decision-making. Although there is substantial research on case studies of mangrove management, global comparisons of mangrove governance are lacking. This research aims to fill this gap by comparing relationships among qualities of governance across mangrove social-ecological systems worldwide. Through a systematic literature search and screening process, we identified 65 articles that discussed mangrove governance and conservation. Case studies in these articles, drawn from 39 countries, were categorized as top-down, bottom-up, or comanaged and thematically coded to assess the influence of eight principles of good governance in mangrove conservation success. Across all three governance systems, the principles of legitimacy, fairness, and integration were most important in determining conservation success or failure. These principles are closely related to the concept of procedural justice, highlighting the importance of stakeholder inclusion throughout all stages of mangrove management. Thus, we recommend clearly defined roles for all governance actors, transparent communication of policy development to stakeholders, fairness in both process and outcome, and careful consideration of sustainable access to conservation resources.     

Microbial communities in swamps of four mangrove reserves driven by interactions between physicochemical properties and microbe in the North Beibu Gulf,China

Environmental Science and Pollution Research - Mangroves are distributed in coastal and estuarine regions and are characterized as a sink for terrestrial pollution. It is believed that complex...     

遗传工程菌Fhhh降解精对苯二甲酸与mnp基因表达

跨界融合构建的遗传工程菌Fhhh及其亲株黄孢显毛平革菌 (PC) ,降解精对苯二甲酸的比降解率受到Mn2 + 、酒石酸铵、H2 O2 、pH共 4因素的影响 .除pH值外 ,其余 3个因素影响 2菌株比降解率大小的排序完全一致 .pH值对PC菌的影响排序处于第 3位 ,对Fhhh则处于第 1位 .Fhhh比降解率比PC高出 11 11% ;mnp基因表达的锰过氧化物酶 (MnP)比活力水平比PC高出 15 2 2 % .降解精对苯二甲酸 4因素优化水平 ,也是mnp基因表达的优化条件 .比降解率与MnP的比活力水平之间有显著或极显著正相关性 (r>r0 .0 5( 4) ,r >r0 .0 1( 4) ) .研究结果为高效处理精对苯二甲酸废水提供了重要的分子生物学依据     

海底油气管道的泄漏及预防

介绍了海底油气管道铺设特点,分析了海底管道破裂的原因主要是第三方损害,其次还有物理损伤、机械损伤、管线材质缺损、材料疲劳、管线内外表面腐蚀、不可抗力和外界条件变化等。提出了海底管道泄漏的有效预防措施,主要包括预防第三方损害和管线腐蚀、提高泄漏检测和监测能力、制定应急响应计划、鼓励公众参与、迅速实施应急响应计划五部分。