EKG电极真空–电渗处理软黏土室内试验研究

针对真空–电渗法在软基处理中存在金属电极易腐蚀,试验后期排水效率低等问题,利用自主研发的装置试验了EKG电极在电渗法、真空预压法、真空–电渗法、阴极直排式真空–电渗法下的排水效果,通过监测排水量、电流、pH值、沉降和处理后的强度等指标将上述方法进行比较,结果表明:(1)真空–电渗法处理后排水量最大,沉降更明显,土体强度更大;(2)阴极直排法在前8 h,排水量高于双侧排水真空–电渗法,土体内pH值更稳定,土体表面更均匀;阴极直排法能在一定时间内改善传统真空–电渗法在阳极真空预压与电渗相互抑制的情况,如果将阴极直排法与双侧排水真空–电渗法相结合,能够为扩大真空–电渗联合法的应用范围提供新的研究思路。

太沙基三维固结方程在一维情况下精确解的物理意义解释

通过建立太沙基一维固结理论体系下位移与孔隙水压力的耦合方程,说明能否体现位移和孔压的耦合关系并不是比奥固结理论优于太沙基固结理论的方面,耦合方程的真正价值在于充当了求解具有更多未知数的比奥固结方程的必要数学条件。相关成果有利于更好地理解固结方程及相关问题的本质,推进固结方程的应用。

氮、磷吸附/解吸法确定环保疏浚深度方法探讨——以太原汾河示范段为例

有效疏浚深度是决定疏浚工程造价和治理效果的关键指标,目前我国现行标准规范尚未明确底泥营养盐浓度的标准,对营养盐超标河湖污染底泥的评价和有效疏浚深度确定十分不利。以太原汾河示范段为例,取其代表性柱状样0.3~0.4、0.9~1.0、1.4~1.6、1.9~2.0 m深度的底泥,分别设计Ⅰ类~劣Ⅴ类氨氮(NH4^+-N)、正磷酸盐(PO4^3-)的模拟水和柱状样实际上覆水,进行氮、磷吸附/解吸试验,并分析不同深度底泥氮、磷吸附/解吸特征。结果表明:柱状样1.6 m深度以内底泥中NH4^+-N对水体呈释放状态,1.9 m深度底泥对水体中NH4^+-N具一定吸附性;1.6 m深度以内底泥中PO4^3-对水体有释放风险,1.9 m深度底泥对水体中PO4^3-具一定吸附性;1.3 m深度底泥中总氮(TN)、NH4^+-N浓度出现较明显的拐点,1.6 m深度底泥中总磷(TP)浓度出现较明显的拐点。结合底泥对上覆水体影响及底泥中氮、磷浓度垂向变化等因素,确定太原汾河示范段有效疏浚深度为1.6 m。

4种真空预压土体固结度预测方法及其效果对比

以天津临港经济区真空预压工程实测地表沉降数据为基础,使用双曲线法、三点法、Asaoka法及孔压固结度法对地基的固结度进行预测。结果表明:使用双曲线法预测结果较小且人为影响大,影响工程经济性;三点法预测结果较大,不能保证工程质量;从欠固结土沉降计算理论出发,认为孔压固结度法计算结果可以作为预测结果下限值,而Asaoka法与实测结果较吻合。建议在类似工程中改变单一的双曲线评价方法,采用3种预测方法对比分析为主、孔压固结度法为辅的方法综合评判。

Vertical drainage capacity of new electrical drainage board on improvement of super soft clayey ground

As an advanced polymer composites electro-kinetic geosynthetics, the electro-osmotic vertical drainage(EVD) board could drain water quickly and accelerate consolidation process. However, the drainage rate was mainly impacted by the vertical drainage capability. Therefore, vertical drainage capability at the top of EVD board was theoretically analyzed. Basic requirements for drainage at the top of the board were summed up, as well as the formula of anode pore pressure when losing the vertical drainage capability. Meanwhile, a contrast test on the top and bottom drainage capacities was conducted. In use of the advanced EVD board, the voltage potential and pore pressure of anode were measured. Moreover, the derived formulas were verified. The result shows that the decrease of electric force gradient had an observable impact on the drainage capability. There was nearly no difference between the energy consumption for the two drainage methods. Although a little less water was discharged, the top drainage method had more advantages, such as high initial drainage velocity, few soil cracks, low anode water content and high soil strength. All of these show that the super soft soil ground could be consolidated quickly in use of the advanced EVD board through the top drainage. The top drainage method could efficiently improve the drainage effect, decrease the energy consumption and speed up the project proceeding.

中风化泥质砂岩遇水软化特性及其对锚碇基础承载性能的影响

对于广西滨海公路龙门大桥西锚碇基底中风化泥质砂岩,开展了天然和浸水饱和两种状态下单轴压缩试验和圆盘劈裂试验,研究了锚碇基底岩石在遇水前后的强度变化规律,结果表明,中风化泥质砂岩遇水后抗压强度降低20.1%,抗拉强度降低48.7%,抗拉强度显著降低。开展了天然状态和浸水饱和状态下岩石—混凝土界面大直剪试验,研究了锚碇基岩遇水软化对摩擦系数的影响规律,结果表明,摩擦系数随着粗糙度的增大而增大,岩石浸水饱和后,摩擦系数降低幅度在4%以内,降低程度较小。设置基岩软化系数为0.8,使用PLAXIS 3D有限元软件,建立岩石遇水软化前后的有限元模型,研究结果表明,锚碇基底岩石遇水饱和后,锚碇最大水平位移增加4.6%,锚碇基础内力减少1.3%,围护结构中的桩、槽内力增加3.8%、3.3%。综合来看,风化泥质砂岩遇水软化后,锚碇基础及围护结构的变形和内力变化不明显。

桩—墙咬合式基坑围护的环向效应分析

圆形锚碇具有良好的变形与受力特性,被广泛用于悬索桥锚碇的建设。针对广西龙门大桥东锚碇采用的大直径桩+地下连续墙咬合的新型圆形基坑围护形式,采用有限元软件PLAXIS模拟了岩质地基中圆形桩—墙咬合式基坑围护在开挖时的受力变形特性,结果表明桩—墙能较好地协同受力与变形。在此基础上,对比分析了咬合式桩墙围护与光滑圆形地连墙的环向效应,分析结果表明,桩—墙咬合式基坑围护能够充分地利用圆形结构的环向效应,从而优化围护受力。