MICP联合纤维加筋改性钙质砂力学特性研究

钙质砂是中国南海岛礁工程建设的主要建筑材料和地基土成份,其具有高孔隙、易破碎和强度低等不良工程地质特性。为改善钙质砂力学性能,提高其工程可靠性,提出利用微生物诱导碳酸钙沉积（MICP）协同纤维加筋改性钙质砂。文章通过开展无侧限抗压试验以及扫描电镜测试,对比分析不同纤维掺量下MICP固化钙质砂的力学响应特性及微观破坏机理。结果表明：（1）MICP技术能够有效固化钙质砂,并提升其力学强度;（2）纤维能够增加细菌定殖面积,提升碳酸钙沉积量,并由此提升试样延性和韧性,降低刚度;（3）应力应变曲线呈阶梯状多峰特征。在应力上升阶段,砂颗粒和碳酸钙会发生局部破碎;在峰后应力下降阶段,碳酸钙、砂颗粒、纤维的胶结作用增强了纤维的抗拔性能,限制了破坏面的发展;（4）碳酸钙、砂颗粒、纤维的耦合胶结作用是纤维加筋改善试样韧性、延性的根本原因。     

Effect of lithology and structure on seismic response of steep slope in a shaking table test

Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occurrence of slope failures. The present study carried out experiments on four rock slopes with steep angle of 60° by means of a shaking table. The recorded Wenchuan earthquake waves were scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope were analyzed, with much effort on timedomain acceleration responses to horizontal components of seismic shaking. It was found that the amplification factor of peak horizontal acceleration, RPHA, was increasing with elevation of each model slope, though the upper and lower halves of the slope exhibited different increasing patterns. As excitation intensity was increased, the drastic deterioration of the inner structure of each slope caused the sudden increase of RPHA in the upper slope part. In addition, the model simulating the soft rock slope produced the larger RPHA than the model simulating the hard rock slope by a maximum factor of 2.6. The layered model slope also produced the larger RPHA than the homogeneous model slope by a maximum factor of 2.7. The upper half of a slope was influenced more seriously by the effect of lithology, while the lower half was influenced more seriously by the effect of slope structure.     

登陆热带气旋降水增幅的合成诊断分析

利用NCEP/NCAR再分析资料,采用动态合成分析方法,对登陆后降水增幅类和非增幅类热带气旋的大尺度环流特征做了合成分析和动力诊断.结果表明:增幅类热带气旋处于强经向型环流之中,中高纬度为阻塞形势,高层有急流入口区南侧的强辐散,并与西风槽相互叠加;低层有急流和水汽通道的长时间联结;热带气旋东侧还有次级环流相伴.非增幅类热带气旋环流背景相对平直,高空辐散弱,无西风槽叠加;低空急流减弱迅速,且水汽通道较早出现断裂;无次级环流出现.增幅类热带气旋高层存在显著非地转运动,高层南风急流入口区的强次地转运动和降水增幅紧密相关.     

地震波效应与山体斜坡震裂机理深入分析

"5·12"汶川大地震造成了大量山体斜坡震裂变形和破坏现象,为深入研究其力学机理,通过实例详细调查及地震中体波效应和面波效应的深入分析,认为地震中地震波的作用使山体斜坡表部岩土体尤其是坡肩部位受到量值和方向不断变化的拉张应力作用,该作用在垂直平面内表现为全方位动态变化特点,导致坡肩岩土体具有旋转倾倒和正、反拉作用;与此同时在坡体内部伴随出现潜在剪动作用力及岩土体的开裂和压碎现象,尤其在潜在滑动面上剪切作用力更为集中;此外坡体表面还受到鼓胀拉力和扭力的共同作用.据此可将地震波作用效应划分为4种重要表现形式,即拉一剪破裂效应、界面动应力效应、潜在的楔劈效应和超空(孔)隙水压力激发机制.分析结果与实例及振动模拟结果一致.研究成果可为灾后重建和防灾减灾提供参考.     

Shaking‐table tests of a full‐scale single‐story masonry veneer wood‐frame structure

This paper presents the findings of shaking‐table experiments conducted to examine the seismic performance of a full‐scale, one‐story, wood‐framed structure with masonry veneer. The structure was designed and constructed in accordance with current U.S. code provisions. The veneer was attached to the wood backing with two kinds of metal anchors, corrugated ties fastened with 8d nails and rigid ties fastened with #8 screws. The tests have shown that the use of nails to fasten veneer anchors to the wood studs is highly unreliable due to the high variation of the nail extraction capacity, which can be influenced by the moisture content of the wood. Other than this, both the wood frame and the masonry veneer performed well under severe ground motions far exceeding a design level earthquake for Seismic Design Category D. Good performance was observed for the rigid veneer ties, which were attached to the wood studs with screws. The results have shown that the veneer walls parallel to the direction of shaking helped to restrain the motion of the wood structure and therefore should not be simply treated as added mass. The detailing of wood roof diaphragms requires special attention in consideration of the out‐of‐plane inertia force of the veneer that can be transmitted through the top plate of the wood‐stud wall to the rim joist. Copyright © 2010 John Wiley & Sons, Ltd.     

贵州某机场岩溶发育规律及控制因素分析

在云贵高原碳酸盐岩地区修建机场.岩溶地基稳定性是主要的工程地质问题.通过地表地质测绘、物探及钻探,对贵州某拟建机场地基的岩溶分布进行研究,描述场区岩溶的位置、范围、深度和形态特征,分析岩溶发育因素,评价岩溶地基稳定性,为工程建设提供地质依据.     

某超高层建筑围护桩优化设计

结合苏州某超高层建筑围护结构设计的工程实例,对围护桩配筋进行优化,并对沿周边非均匀配筋和均匀配筋进行强度、刚度和经济比较,同时对围护桩不同长度下基坑受力变形特征进行了研究。结果表明：围护桩采用不均匀配筋及长短交错布置,在受力性能上变化不大,但是能够降低工程造价,缩短工期,获得最佳的经济效益和社会效益。     

SM85型深层搅拌伸缩钻具的研制

介绍了深层搅拌施工技术在工程领域的应用,对比目前深层搅拌施工机械的优缺点,简要介绍了采用伸缩式钻杆的三轴搅拌钻具工作原理及各个部件的组成,以及各部件的工况要求和使用特点,针对几个主要的部件做了详细的介绍。与传统三轴深层搅拌钻机在钻深参数、系统稳定和操作等方面做了比较。     

Geochemical characteristics and oil family classification of crude oils from the Markit Slope in the southwest of the Tarim Basin,Northwest China

Based on the chromatograms of oils and saturated hydrocarbons, biomarkers and stable carbon isotope analyses, the geochemical characteristics and oil family Classification of crude oils from the Markit Slope in the southwest of the Tarim Basin were investigated. The results showed that crude oils from the Markit Slope are divided into two oil family Classification. Oils collected from the Bashituo oilfield in the western part of the Markit Slope are characterized by high contents of tricyclic terpanes, pregnane, and homopregnane, low contents of garmmacerane (G/H<0.20), dibenzofuran, and methyl cyclohexane, and light stable carbon isotopic values (the δ13C values of satu-rated hydrocarbons and aromatic components are less than -34‰ and -32‰, respectively), with the distribution type of steranes being C27>>C28 -32‰ and -30.6‰, respectively), with the distribution type of steranes being C27>C28<相似文献   

三维滑坡推力计算方法探讨

常规二维滑坡推力计算没有考虑其横向变化,导致设计过于保守,三维推力计算方法的提出则能体现滑坡推力的空间分布,解决二维存在的问题.本文在三维极限平衡法统一模型的基础上,建立了求解三维滑坡推力的统一公式.利用实例,通过二维推力计算与三维计算结果的对比分析,获得三维推力的横向分布函数,有效反映出三维滑坡推力的空间分布状态,所...