基坑支护结构施工技术要点与工程实例分析(下)

４地下连续墙施工技术方法４．１要点（１）导墙的修筑精度（宽度、平直度、垂直度和标高等）和强度对成槽施工质量有直接影响,高质量的导墙是高质量槽段的基础,常用的导墙形式如图２所示。图２导墙断面形式示意图（ａ）板型;（ｂ）Ｌ型;（ｃ）倒Ｌ型;（ｄ）槽型导墙...     

红层泥岩半刚性基床结构动态变形试验研究

高速铁路要为列车的高速行驶提供一个高平顺性和稳定性的轨下基础,而路基作为轨道结构的基础,必须具有强度高、刚度大、稳定性和耐久性好的特性。由于红层泥岩属于软岩,工程稳定性差,以红层泥岩作为基床的填料,其刚度明显不足,所以为了弥补基床表层的不足,在其顶部添加一层水泥稳定级配碎石。为了验证这些措施的效果,以便指导工程设计和施工,通过足尺动态模型试验,模拟在实际荷载条件下基床的动态变形特性,结果表明,采用水泥稳定级配碎石作为基床表层填料,静态变形明显降低,能够大幅降低动荷载作用时的动变形,减少了基床结构的永久变形,增强了轨道结构的稳定性。     

Use of clay as a pozzolona in high strength Portland cement and its thermal activation

In this investigation local clay from Cherat mines, Nowshera District, NWFP, Pakistan, has been tested as a pozzolanic material in high strength Portland cement. Thermal treatments were performed as a means of activation of the clay. It was found that thermal treatment of the clay can increase its pozzolanic activity. Different blended mortars, containing different amounts of clay, activated at different temperatures were studied for compressive strength, consistency, and setting times. It was concluded that the mechanical properties of the blended cements were mainly governed by the percentage of incorporation of the calcined clay. Blended cement composition has been formulated, with optimal results of 20% calcined clay at a temperature of 600℃.     

钢、水泥需求“S”形规律的三个转变点剖析

本文剖析了人均钢、水泥消费“S”形轨迹的三个重要转变点, 论述了人均消费量和消费强度变化规律的影响因素和内在机制, 阐述了产业部门钢消费强度的倒“U”形轨迹, 在分析国内外经济结构演变趋势的基础上, 提出我国第二产业占GDP比例已经达到顶点, 指出钢、水泥消费强度顶点大小及到来的时间。     

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

The controlling parameters of early marine carbonate cementation in shoal water and hemipelagic to pelagic domains are well‐studied. In contrast, the mechanisms driving the precipitation of early marine carbonate cements at deeper slope settings have received less attention, despite the fact that considerable volumes of early marine cement are present at recent and fossil carbonate slopes in water depths of several hundreds of metres. In order to better understand the controlling factors of pervasive early marine cementation at greater water depths, marine carbonate cements observed along time‐parallel platform to basin transects of two intact Pennsylvanian carbonate slopes are compared with those present in the slope deposits of the Permian Capitan Reef and Neogene Mururoa Atoll. In all four settings, significant amounts of marine cements occlude primary pore spaces downslope into thermoclinal water depths, i.e. in a bathymetric range between some tens and several hundreds of metres. Radial, radiaxial and fascicular optic fibrous calcites, and radiaxial prismatic calcites are associated with re‐deposited facies, boundstones and rudstones. Botryoidal (formerly) aragonitic precipitates are common in microbially induced limestones. From these case studies, it is tentatively concluded that sea water circulation in an extensive, near‐sea floor pore system is a first‐order control on carbonate ion supply and marine cementation. Coastal upwelling and internal or tidal currents are the most probable mechanisms driving pore water circulation at these depths. Carbonate cements precipitated under conditions of normal to elevated alkalinity, locally elevated nutrient levels and variable sea water temperatures. The implications of these findings and suggestions for future work are discussed.     

超深地下连续墙施工中若干问题探讨

随着地下空间工程的不断发展,超深地下连续墙的应用越来越多,施工的风险也越来越高。结合工程实践,对超深地下连续墙施工方法及施工中存在的若干问题进行探讨、分析,并提出相对应的解决措施。通过采用先进合理的解决措施,超深地下连续墙的施工是完全能达到设计要求的。     

四川盆地震旦系灯影组葡萄状白云岩成因

四川盆地震旦系灯影组发育巨厚的白云岩,其中灯影组二段和四段发育大量具有各种形态的葡萄状白云岩,其直径最长可达75cm,有的平行于层面,有的穿层。剖面资料表明,葡萄状白云岩发育多期等厚环边胶结物,中部残留大量未充填的不规则洞穴,这成为与岩溶喀斯特作用相关的地下溶蚀作用的证据。围岩泥晶白云石为早期海水中原生结晶的产物,后来的胶结物可划分为4期: (1)自泥晶化白云石(部分样品中可见)作为最早的一期胶结物,由于各种生物化学作用和生物作用的影响而紧贴着围岩发育;(2)第2期胶结物纤维状白云石可能为海水中直接沉淀的产物,经历后期成岩作用后,具有完全有序的结构,晶胞参数接近理想值;(3)细—中晶白云石为第3期胶结物,包含纤维状白云石溶蚀残余,形成于构造抬升之后的近地表大气淡水环境;(4)第4期胶结物中—粗晶白云石为埋藏环境下直接结晶的产物,充填了孔洞中心,残留部分未充填孔洞。灯影组受到了岩溶喀斯特作用、胶结作用以及白云石化作用等成岩作用的影响,其中与葡萄状白云岩有关的岩溶喀斯特作用对于灯影组储集层的发育至关重要。对灯影组葡萄状白云岩的研究,不仅有助于深入探讨灯影组储集层成因和演化及灯影组白云岩的成因,而且有助于指导四川盆地前寒武系油气勘探。     

大水位落差深井止水修复方案及实施效果分析

以山西潞安集团和顺李阳煤业有限公司大水位落差深井止水修复方案及实施效果为工程实例,对该工程先后实施的管内注浆法、管外注浆法、衬管固井法、同径水泥架桥法、泄压通桥法等止水修复方案进行了详细分析,总结了其成功的经验,可为类似旧井修复工程或新井施工工程提供借鉴和指导。     

岩石物理化学性质对泰宁丹霞洞穴的形成制约

泰宁丹霞红层由铁钙质混合胶结的较松散固结红色砂砾岩构成,岩石胶结物中CaCO3含量较高,抗压强度极低、孔隙度和含水性均较高。当岩石遇水湿润或浸泡时,或者生物风化过程中受到各种动植物分泌的有机酸作用,岩石胶结物中CaCO3易溶解流失,促使丹霞红层进一步软弱松散。冬季水结冰之后体积会膨胀,所以岩层表面产生片状裂隙。通过裂隙的毛细管效应,孔隙-裂隙水由岩石内部向结冰的表面扩散,在表面张力作用下水呈表面积最小的球状。春季化冻时岩石沿球形片状裂隙自由剥落的片状风化,圆球形洞穴开始形成,随着四季交替,年复一年,间歇性结冰和融化过程,使得洞穴逐渐扩大,形成泰宁丹霞各种形态的洞穴奇观。     

无砟轨道聚氨酯碎石防水联结层单元模型试验研究

基于无砟轨道基床表层水力损伤病害产生机制,提出一种在基床表层上设置聚氨酯碎石防水联结层的水力损伤控制措施。通过建立级配碎石组(J-0)、透水型聚氨酯碎石组(J-5)及致密型聚氨酯碎石组(J-10)3组试验模型,研究聚氨酯碎石防水联结层的静动力特性、疲劳特性与防水特性。结果表明：静力加卸载作用下,J-10残余应变为2.6×10–6,最大位移约为1.0 mm,与下部基床表层级配碎石层变形适应性良好,耗能效果明显,在列车动力荷载水平作用下,可减小基床表层动变形与动应力幅值,增大动应力扩散范围;在长期动力循环荷载作用下,J-0与J-5在注水后结构层动力响应显著增大,而J-10动力响应在加载次数1～2万次后基本保持稳定;试验过程中J-10能够有效防止水分进入基床表层级配碎石层,而J-0与J-5水分不断下渗,引起级配碎石细颗粒损失。研究成果对整治多雨地区无砟轨道基床表层水力损伤病害具有重要的应用价值。