关于严寒地区冻胀土上基础设计问题的探讨

本文阐述了冻胀土类别应按地基规范要求来确定,并提出在冻胀土及强冻胀土上建造房屋应采取的几项措施及注意事项     

草炭土地基冻胀特性试验研究

以吉林东部草炭土为研究对象,制定详细的试验计划方案,对草炭土地基在不同含水量下、不同荷载作用下冻胀和融沉规律进行研究,分析总结草炭土地基的冻胀特性。研究表明草炭土属强冻胀土,草炭土地基浅层冻胀率较高,深层冻胀率略有降低;在不同荷载的作用下,不同层位、不同冻深的草炭土经过冰冻后产生的最大冻胀率不同,产生的平均冻胀率范围为6．95％～21％;不同含水量草炭土地基,在1m以内范围随着含水量的增加,最大冻胀率也提高,变化范围为12％～17％,比较解冻融化后膨胀率,融沉量所占的比重较高,如1．6m冻深范围内经过冻胀解冻后融沉为总平均冻胀量的30％～40％。公路建设应根据其特性,进行合理设计及施工,避免草炭土地区公路产生病害。     

季冻土地基盖板涵基础浅埋的构造措施

白河林业局，自１９８７年以来，对近百座１Ｍ，盖板涵基础采取了浅埋的方法，取得了明显的经济效益，基础浅埋的措施是应用０．５ｍ厚的砂砾垫层，及０．６ｍ厚浆砌块石，使涵洞形成整体式结构，这样既满足了地基承载要求，又防止了冻胀破坏。对基础最小埋深应用（黑交法）验算结果是：弱冻胀土为１．０９ｍ冻胀土为１．１９５ｍ。     

浅谈冻土基础的选择

多年冻土区要把基础设在冻土层以下一般是不现实的,在设计中要考虑许多因素。当地基土为无地下冰的纯净砂、砾石和基岩时,尽管地基标高以下地基土是冻结的,基础设计一般仍与温带的设计方法相同,这种地基土季节性冻胀和下沉相当小,可忽略不计。基础的最小埋置深度不宜小于1.5米;在降雨量很少的地区,有时可遇到细粒土中     

建筑工程基础冻害治理调研

建筑工程基础冻害治理调研内蒙古乌尔旗汉林业局赵平安，姚森，袁月芳建筑工程基础冻害，主要是由于地基受季节冻土的冻胀和多年冻土的融沉所致。季节冻土冻胀产生冻害的治理办法已经规范化，如基础基底设在规范要求防止冻害埋置的深度，或回填非冻胀性土壤，基础侧面回填...     

林业严寒地区冻胀土地基碎毛石垫层的应用

林业严寒地区冻胀土地基碎毛石垫层的应用黑龙江省林业科学院李建强通过对伊春及附近几个林业局房屋质量问题的调查，发现地基冻胀对建筑的危害严重，特别是地下水位较高，冰冻深度超过地下水位１ｍ以上的地区，危害尤其严重。为缓解冻胀对基础的破坏，我们在基础底部饱和...     

林业严寒地区冻胀土地基碎毛石垫层的应用

林业严寒地区冻胀土地基碎毛石垫层的应用李建强，柴风林（黑龙江省林业科学院）（苇河林业局）通过对伊春林业局房屋质量问题的调查，发现地基冻胀对建筑物的危害严重，尤其在地下水位较高，冰冻深度超过地下水位１ｍ以上地区。为缓解冻胀对基础的破坏，在基础底部饱和水...     

不良地基、异常地基的处理与加固方法

论述了在建造建筑物之前,针对不良地基土及异常地基土的处理方法及加固方案。     

用森铁路基改建的运材公路冻害的实验研究

通过实验观测研究,认为产生冻害的原因主要是在高路堤边坡段与低路堤路段的土质成分亚粘土含量高,且施工辗压时又未能控制最佳含水量时的密实度。改善的措施是填入一定比例的砾石料,把路基土成为冻胀率小于1％的非冻胀性土,以消除细粒岩土聚集水分的固有性质。     

膨胀土地基工程设计的体会

膨胀土地基在建筑设计中非常重要。如地基发生变形,整栋楼房就要开裂、倒塌,膨胀土地基的胀缩变形是由于地基土的胀缩性及其含水量的变化引起的,因此,作者着重地论述了建筑物开裂主要原因是由:1.建筑场地土的胀缩性能及其分布的不均匀性;2.促使地基土含水量变化的外界条件;3.建筑物抵抗或适应地基不均匀变形的能力所造成的。     

季节性冰冻地区路基聚冰防治措施浅析

我国东北季节性冰冻地区的路基若土体中含有较多的水,在温度下降的时候,会发生程度不同的聚冰、冻胀现象。由于土体含水量、土体毛细作用的强弱及温度变化速度的不同,又将产生轻度冻胀直至翻浆等不同程度的病害。本文对季节性冰冻地区聚冰现象提出了一些防治措施及建议。     

浅谈公路翻浆病害的原因及预防处理措施

结合冻融地区出现的公路翻浆现象,进行了病害原因的分析,并从设计、施工、养护等方面提出了相应的处理措施和意见。     

浅谈公路翻浆的原因及防治

公路翻浆是常见公路病害,尤其是东北地区更为严重,本文结合大兴安岭地区气候、地质等特点对产生翻浆的原因及常见处治方法进行了论述.     

Frost resistance and ice nucleation in leaves of five woody timberline species measured in situ during shoot expansion

Frost resistance and ice nucleation temperatures of leaves, from bud swelling until after full expansion, were measured in situ for five major woody timberline species with recently developed field freezing equipment. Frost resistance determined in situ on leaves of attached twigs was significantly higher than values determined on detached leaves in laboratory tests (e.g., the temperature at which incipient frost damage was observed (LTi) was 1.2 degrees C higher for detached leaves than for attached leaves of Picea abies (L.) Karst.). Frost resistance of leaves of all species changed significantly during shoot expansion (e.g., changes of 7.2 and 11 degrees C for Rhododendron ferrugineum L. and Larix decidua Mill., respectively). Expanding leaves (between 0 and 60% of full expansion) were the most sensitive to frost, with LTi values ranging from -3.4 degrees C in R. ferrugineum to -6.3 degrees C in L. decidua. Among the studied species, P. abies and R. ferrugineum were the most frost sensitive throughout the shoot elongation period. In situ freezing patterns of leaves of attached twigs also differed from those of leaves of excised twigs. During leaf expansion, two distinct freezing exotherms were always registered in situ. The first freezing event (E1, high-temperature exotherm) was recorded at -1.5 +/- 0.2 degrees C and reflected extracellular ice formation. Exposure of leaves to temperatures at which E1 occurred was, in all cases, noninjurious. The low-temperature exotherm (E2) mostly coincided with frost damage, except for some stages of leaf expansion in R. ferrugineum and P. abies, indicating that in situ freezing exotherms were not accurate estimators of frost damage in these species.     

Winter frost resistance of Pinus cembra measured in situ at the alpine timberline as affected by temperature conditions

Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950 m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN?)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN? (-196 °C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT??) of leaves was <-?75 °C and that of buds was less (-70.3 °C), matching the lowest water contents. In midwinter, in situ freezing exotherms of leaves, buds and the xylem were often not detectable. Ice formed in the xylem at a mean of -2.8 °C and in leaves at -3.3 °C. In situ WFR of P. cembra was higher than that obtained on detached twigs, as reported earlier. In situ LN?-quenching experiments were lethal in all cases even when twigs of P. cembra were exposed to an in situ frost hardening treatment (12 days at -20 °C followed by 3 days at -50 °C) to induce maximum WFR. Temperature treatments applied in the field significantly affected the actual WFR. In January a frost hardening treatment (21 days at -20 °C) led to a significant increase of WFR (buds: -62 °C to <-?70 °C; leaves: -59.6 °C to -65.2 °C), showing that P. cembra was not at its specific maximum WFR. In contrast, simulated warm spells in late winter led to premature frost dehardening (buds: -32.6 °C to -10.2 °C; leaves: -32.7 to -16.4 °C) followed by significantly earlier bud swelling and burst in late winter. Strikingly, both temperature treatments, either increased air temperature (+10.1 °C) or increased soil temperature (+6.5 °C), were similarly effective. This high readiness to frost harden and deharden in winter in the field must be considered to be of great significance for future winter survival of P. cembra. Determination of WFR in field re-growth tests appears to be a valuable tool for critically judging estimates of WFR obtained on detached twigs in an ecological context.     

竹塑复合材料吸水性能的研究

对楠竹/新PE、楠竹/回收PE、杂竹/回收PE 3种竹塑复合材料的吸水性能进行了研究,结果表明:(1)温度是影响竹塑复合材料吸水厚度膨胀率和吸水率的主要因素之一。(2)3种竹塑复合材料厚度方向吸水膨胀性和吸水率表现为:杂竹/回收PE材料吸水膨胀性最大,楠竹/新PE次之,楠竹/回收PE最小。(3)杂竹/回收PE在80℃时的吸水率是室温下的3.5倍;楠竹/新PE和楠竹/回收PE在80℃条件下的吸水率均是室温下的3倍。(4)楠竹/回收PE在80℃水浴中的厚度方向吸水膨胀率是55℃下的1.4倍,是室温下的2倍;楠竹/新PE80℃水浴下吸水膨胀率是55℃下的1.2倍,是室温下的1.9倍;杂竹/回收PE 80℃水浴下吸水膨胀率是55℃下的1.6倍,是室温下的2倍多。(5)光学显微镜和扫描电镜观察后发现,吸水后竹塑复合材料除了竹纤维发生膨胀之外,材料的内部结构没有发生变化,即竹塑复合材料是一种具有良好抗湿膨胀性能的新型复合材料。     

凤县花椒春季霜冻的气候分析

本文对凤县花椒霜冻的气候因素进行了分析。结果认为,凤县花椒霜冻在时间分布上主要集中出现于春4月上、中旬。霜冻在空间分布上具有随海拔升高而加重、随地域不同而多变的特点。凤县霜冻的发生以"平流+辐射霜冻"为主,以"平流霜冻"或"平流+辐射霜冻"对花椒造成的危害最大。花椒受害的严重程度还与低温程度、降温强度、降温时的空气湿度、低温持续时间、霜冻类型、霜冻出现时间及椒园管理状况密切相关。     

提取六月霜中有效物质的工艺优化

用水提法对六月霜的有效物质进行提取,并设计正交试验以总黄酮和可溶性固形物的含量为衡量指标,确定六月霜的最佳浸提条件。结果表明:在80℃条件下,用35倍于六月霜重量的蒸馏水,水浴浸提80min,且六月霜的颗粒大小为200目,六月霜的有效物质提取效果最佳,其粗总黄酮量得率最高。     

降香黄檀在肇庆市属国有林场适生性评价

薇甘菊是一种危害严重的外来入侵物种,也是我国林业检疫性有害生物。文章根据薇甘菊的生物学特性,选择对菊科植物有高活性的药剂成分进行复配研制药剂,经室内和林间的药效试验,筛选出能高效防治薇甘菊且对环境安全的新药剂——24%二氯吡啶酸·2,4-滴水剂,商品名为"紫薇清"。