氧化镁碱激发矿粉-膨润土-土竖向屏障材料阻隔铅污染物的化学渗透膜效应

李双杰; 伍浩良; 傅贤雷; 蒋宁俊; 万佳磊; 李江山; 杜延军

doi:10.11779/CJGE202206012

氧化镁碱激发矿粉-膨润土-土竖向屏障材料阻隔铅污染物的化学渗透膜效应 English Version

1.
东南大学交通学院岩土工程研究所，江苏南京 210096
2.
香港科技大学土木与环境工程系，香港 999077
3.
中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室，湖北武汉 430071

基金项目:

国家重点研发计划项目 2018YFC1803100

国家重点研发计划项目 2018YFC1802300

国家自然科学基金项目 41877248

国家自然科学基金项目 42177133

详细信息

作者简介:
李双杰(1997—)，男，硕士研究生，主要从事环境岩土工程学习和研究。E-mail: 220193046@seu.edu.cn

通讯作者:
杜延军, E-mail: duyanjun@seu.edu.cn

中图分类号: TU43
计量
- 文章访问数: 226
- HTML全文浏览量: 33
- PDF下载量: 130
出版历程
- 收稿日期: 2021-07-18
- 网络出版日期: 2022-09-22
- 刊出日期: 2022-05-31

Experimental study on chemico-osmotic membrane behaviors of reactive MgO-activated slag-bentonite backfill in vertical cutoff walls exposed to Pb-laden groundwater

1.
Institute of Geotechnical Engineering, Southeast University, Nanjing 210096, China
2.
Department of Civil & Environmental Engineering, Hong Kong University of Science & Technology, Hong Kong 999077, China
3.
State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China

摘要

摘要: 采用活性氧化镁激发粒化高炉矿粉（GGBS）制备氧化镁激发矿粉-膨润土-土（MSBS）竖向阻隔屏障材料。通过一维土柱化学渗透试验，研究了硝酸铅（Pb(NO₃)₂）污染液浓度对MSBS阻隔屏障材料的阻隔性能参数包括化学渗透膜效率系数、有效扩散系数和阻滞因子的影响规律，对比分析了MSBS、土-膨润土（SB）和膨润土防水毯（GCL）竖向屏障材料的阻隔性能参数的差异特征。结果表明：MSBS屏障材料在Pb(NO₃)₂污染液中表现出明显的化学渗透膜效应，其化学渗透膜效率系数随着Pb(NO₃)₂污染液浓度增加迅速减小。MSBS阻隔屏障材料Pb²⁺的有效扩散系数随Pb(NO₃)₂污染液浓度增大略有增加，但变化幅度明显低于SB屏障材料。MSBS的阻滞因子受Pb²⁺浓度影响不显著，而SB竖向阻隔屏障对于Pb²⁺的阻滞因子则随其浓度增加而显著降低。
- MgO-GGBS /
- MSBS /
- 化学渗透膜效应 /
- 有效扩散系数 /
- 阻滞因子
Abstract: The reactive magnesia (MgO) is used as an alkali activator to activate granulated blast furnace slag (GGBS) to prepare alkali activated slag-bentonite-soil vertical barrier (MSBS) material. The chemico-osmotic memberane behavior test using lead nitrate Pb(NO₃)₂ solutions with different concentrations as testing liquids is conducted on the MSBS specimen, and the effects of Pb(NO₃)₂ concentration on the Pb²⁺ containment performance including chemico-osmotic efficiency coefficient, effective diffusion coefficient and retardation factor are evaluated. Comparative assessment of performance is made between the MSBS material in this study and other engineered barrier materials including soil-bentonite (SB) vertical cutoff wall backfill and geosynthetic clay liner (GCL) reported in previously published studies. The results show that the MSBS backfill has noticeable chemical-osmotic membrane behavior, and the chemico-osmotic efficiency coefficient decreases rapidly with the increasing Pb²⁺ concentration. The effective diffusion coefficient of Pb²⁺in the MSBS increases slightly with the increasing Pb²⁺concentration, and its change magnitude is significantly lower than that for the SB backfill materials. The retardation factor for Pb²⁺ in the MSBS backfill remains practically constant with the increasing Pb²⁺concentration, whereas it decreases significantly with the increasing Pb²⁺ concentration for the SB backfill materials.
- MgO-GGBS /
- MSBS /
- chemico-osmotic efficiency /
- effective diffusion coefficient /
- retardation factor

HTML全文

0. 引言

劲性水泥搅拌桩（SDCM column）也称“混凝土芯搅拌桩”,是一种由水泥搅拌桩(DCM column)壳和中心处较小面积预制混凝土芯桩组成的复合材料桩。按照芯桩与DCM桩壳二者长度间的相对关系,SDCM桩分为3种类型：芯桩长度小于DCM桩壳长度的短芯SDCM桩、芯桩长度等于DCM桩壳长度的等芯SDCM桩和芯桩长度大于DCM桩壳长度的长芯SDCM桩。较之传统的DCM桩,SDCM桩的竖向和水平向承载力高,沉降控制效果好。它既可作为桩基础,也可作为复合地基的竖向增强体,在国内外都得到了大量应用^[1-2]。

很多学者通过室内外试验和数值模拟等方法,从承载力、荷载传递机制和控沉效果等方面对短芯SDCM桩和短芯SDCM桩复合地基进行了较为系统的研究。凌光荣等^[3]、董平等^[4]和吴迈等^[5]通过现场单桩载荷试验研究了SDCM桩的轴向承载特性。试验发现,芯桩的插入使搅拌桩桩侧摩阻力充分发挥,SDCM桩的竖向承载力可高于混凝土灌注桩。Voottipruex等^[6]采用三维有限元法研究了芯桩长度和截面积等因素对SDCM桩竖向和水平向承载力、芯桩轴力和弯矩分布的影响。吴迈等^[7]、丁永君等^[8]和顾士坦等^[9]采用理论分析和现场实测芯桩桩身应力的方法研究了SDCM桩的荷载传递特性。Wonglert等^[10-11]基于室内模型试验成果,提出短芯SDCM桩有土体破坏、芯桩底部破坏和搅拌桩壳顶部破坏3种破坏模式,研究了芯桩长度和搅拌桩壳强度对悬浮SDCM桩竖向承载力和破坏模式的影响。Wang等^[12]通过现场荷载板试验,比较了刚性基础下SDCM桩复合地基与DCM桩复合地基的竖向承载力。Voottipruex等^[13]和Wang等^[14]进行了路堤下SDCM桩复合地基现场试验,比较了柔性基础下SDCM桩复合地基与DCM桩复合地基的沉降控制效果。叶观宝等^[15-16]提出了悬浮SDCM桩复合地基桩-土应力比和沉降的计算方法。杨涛等^[17]建立了端承短芯SDCM桩复合地基的固结计算模型。

近年来,随着长芯SDCM桩在中国的逐渐应用,其承载机理和设计理论的研究开始受到学术界的关注。陈华顺等^[18]和程博华^[19]分别提出了长芯SDCM桩桩侧摩阻力和竖向承载力的计算方法。杨涛等^[20]给出了端承长芯SDCM桩复合地基固结解析解,但该解答无法用于分析悬浮长芯SDCM桩复合地基的固结问题。有鉴于此,本文研究悬浮长芯SDCM桩复合地基的固结计算方法,分析悬浮长芯SDCM桩复合地基的固结特性,进一步完善SDCM桩复合地基的固结计算理论。

1. 固结模型与基本假定

1.1 轴对称固结模型

图1给出悬浮长芯SDCM桩复合地基轴对称固结模型,r和z分别是径向和竖向坐标。r_e为一根SDCM桩的影响区半径,可由桩的间距和布桩方式计算得到。水泥搅拌桩壳外半径和长度分别为r_p和L_p=H₁,上部SDCM桩的置换率为m（m=(r_p/r_e)²）,压缩模量为E_p。芯桩打穿水泥搅拌桩壳,其半径和长度分别为r_sp和L_sp（L_sp=H₁+H₂）,压缩模量为E_sp。芯桩的截面含芯率为ρ（ρ=(r_sp/r_p)²）。根据水泥搅拌桩壳和芯桩的长度将复合地基加固区分为Ⅰ和Ⅱ二部分,加固区Ⅰ内桩间土的厚度、渗透系数、固结系数和压缩模量分别为H₁,k_v1,c_v1,E_s1,加固区Ⅱ内桩间土的厚度、渗透系数、固结系数和压缩模量分别为H₂,k_v2,c_v2,E_s2。下卧层土厚度、渗透系数、固结系数和压缩模量分别为H₃,k_v3,c_v3,E_s3。复合地基总厚度H= H₁+H₂+H₃。

图 1 复合地基固结模型

Figure 1. Consolidation model for composite ground

下载: 全尺寸图片幻灯片

1.2 基本假定

本文公式推导采用如下假定：①地基土完全饱和,水的流动符合Darcy定律；②搅拌桩壳不排水；③芯桩桩端以下的下卧层土和搅拌桩壳以下芯桩桩端以上的土仅发生径向渗流；④芯桩与搅拌桩壳间无相对滑移,加固区中任意深度处的桩和土的竖向应变相等；⑤大面积均布荷载p瞬时施加,在待加固地基中引起的竖向附加应力沿深度均布；⑥土的渗透系数和压缩模量不随固结而变化。

2. 固结方程与定解条件

2.1 固结方程

基于前述基本假定,参考杨涛等^[20-21]的研究,可得到荷载p瞬时施加情况下悬浮长芯SDCM桩复合地基得固结方程如下：

。

${\begin{cases} \frac{\partial {\bar{u}}_{s 1}}{\partial t} = c_{v 1 e} \frac{\partial^{2} {\bar{u}}_{s 1}}{\partial z^{2}} \begin{matrix} \end{matrix} (0 \leq z < H_{1}), \\ \frac{\partial {\bar{u}}_{s 2}}{\partial t} = c_{v 2 e} \frac{\partial^{2} {\bar{u}}_{s 2}}{\partial z^{2}} \begin{matrix} \end{matrix} (H_{1} \leq z < H_{1} + H_{2}), \\ \frac{\partial {\bar{u}}_{s 3}}{\partial t} = c_{v 3 e} \frac{\partial^{2} {\bar{u}}_{s 3}}{\partial z^{2}} \begin{matrix} \end{matrix} (H_{1} + H_{2} \leq z \leq H) 。 \end{cases}$

(1)

$c_{v 1 e} = (1 + \frac{m [ρ E_{s p} + (1 - ρ) E_{p}]}{(1 - m) E_{s 1}}) c_{v 1}$ ,

(2)

$c_{v 2 e} = (1 + \frac{m ρ E_{s p}}{(1 - m ρ) E_{s 2}}) (\frac{1 - m}{1 - m ρ}) c_{v 2}$ ,

(3)

$c_{v 3 e} = (1 - m ρ) c_{v3} 。$

(4)

式中 ${\bar{u}}_{s 1}$ , ${\bar{u}}_{s 2}$ , ${\bar{u}}_{s 3}$ 分别为加固区Ⅰ、Ⅱ中桩间土和下卧层土中任意深度z处的平均超静孔隙水压力；c_v1e,c_v2e,c_v3e分别为考虑劲性桩和芯桩影响的加固区Ⅰ、Ⅱ中桩间土和下卧层土的等效竖向固结系数。

2.2 定解条件

（1）边界条件

考虑复合地基上边界排水、下边界不排水的单面排水情况,边界条件如下：

$z = 0, {\bar{u}}_{s 1} = 0$ ,

(5)

$z = H, \frac{\partial {\bar{u}}_{s 3}}{\partial z} = 0$ 。

(6)

（2）孔压和水流连续性条件

考虑到 $(1 - m) {\bar{u}}_{s 1}$ 和 $(1 - m ρ) {\bar{u}}_{s 2}$ 分别为加固区Ⅰ和加固区Ⅱ内任意深度处的平均孔压,可得加固区Ⅰ与加固区Ⅱ分界面处、加固区Ⅱ与下卧层分界面处孔压和水流连续性条件如下：

z=H₁时,

$(1 - m) {\bar{u}}_{s 1} = (1 - m ρ) {\bar{u}}_{s 2}$ ,

(7)

$(1 - m) k_{v 1} \frac{\partial {\bar{u}}_{s 1}}{\partial z} = (1 - m ρ) k_{v 2} \frac{\partial {\bar{u}}_{s 2}}{\partial z}$ 。

(8)

z=H₁+H₂时,

$(1 - m ρ) {\bar{u}}_{s 2} = {\bar{u}}_{s 3}$ ,

(9)

$(1 - m ρ) k_{v 2} \frac{\partial {\bar{u}}_{s 2}}{\partial z} = k_{v 3} \frac{\partial {\bar{u}}_{s 3}}{\partial z}$ 。

(10)

（3）初始条件

荷载施加的瞬时,桩间土和下卧层土中没有竖向变形。参照杨涛等^[20-21]的研究,容易写出如下初始条件：

${\bar{u}}_{s 1} (z, 0) = \frac{p}{1 - m}$ ,

(11)

${\bar{u}}_{s 2} (z, 0) = \frac{p}{1 - m ρ}$ ,

(12)

${\bar{u}}_{s 3} (z, 0) = p$ 。

(13)

3. 固结解析解

3.1 方程与定解条件的函数变换

为便于求解,进行如下函数变换：

${\begin{cases} {\hat{u}}_{s 1} = (1 - m) {\bar{u}}_{s 1}, \\ {\hat{u}}_{s 2} = (1 - m ρ) {\bar{u}}_{s 2}, \\ {\hat{u}}_{s 3} = {\bar{u}}_{s 3} 。 \end{cases}$

(14)

显然, ${\hat{u}}_{s 1}$ 和 ${\hat{u}}_{s 2}$ 分别是复合地基上、下加固区任意深度处的平均超静孔隙水压力。将式（14）代入固结控制方程式（1）和定解条件式（5）～（13）,则变换后的复合地基固结控制方程和求解条件如下：

${\begin{cases} \frac{\partial {\hat{u}}_{s 1}}{\partial t} = c_{v 1 e} \frac{\partial^{2} {\hat{u}}_{s 1}}{\partial z^{2}} \begin{matrix} \end{matrix} (0 \leq z < H_{1}), \\ \frac{\partial {\hat{u}}_{s 2}}{\partial t} = c_{v 2 e} \frac{\partial^{2} {\hat{u}}_{s 2}}{\partial z^{2}} \begin{matrix} \end{matrix} (H_{1} \leq z < H_{1} + H_{2}), \\ \frac{\partial {\hat{u}}_{s 3}}{\partial t} = c_{v 3 e} \frac{\partial^{2} {\hat{u}}_{s 3}}{\partial z^{2}} \begin{matrix} \end{matrix} (H_{1} + H_{2} \leq z \leq H) 。 \end{cases}$

(15)

$z = 0 ： {\hat{u}}_{s 1} = 0$ ,

(16)

$z = H ： \frac{\partial {\hat{u}}_{s 3}}{\partial z} = 0$ ,

(17)

z=H₁,

${\begin{cases} {\hat{u}}_{s 1} = {\hat{u}}_{s 2} \\ k_{v 1} \frac{\partial {\hat{u}}_{s 1}}{\partial z} = k_{v 2} \frac{\partial {\hat{u}}_{s 2}}{\partial z} \end{cases}$ ,

(18)

z=H₁+H₂,

${\begin{cases} {\hat{u}}_{s 2} = {\hat{u}}_{s 3} \\ k_{v 2} \frac{\partial {\hat{u}}_{s 2}}{\partial z} = k_{v 3} \frac{\partial {\hat{u}}_{s 3}}{\partial z} \end{cases}$ ,

(19)

${\hat{u}}_{s 1} (z, 0) = {\hat{u}}_{s 2} (z, 0) = {\hat{u}}_{s 3} (z, 0) = p$ 。

(20)

3.2 固结解析解

显然,式（15）,（16）～（20）分别是瞬时荷载p作用在由复合地基上、下加固区复合土和下卧层土组成的三层土系统固结问题的固结方程和定解条件。与瞬时荷载p作用下的三层天然地基固结问题相比,只是各层天然地基土的固结系数c_v1,c_v2和c_v3分别被c_v1e,c_v2e和c_v3e代替而已。设三层土系统中土层i的渗透系数为k_vi(i=1,2,3),则其压缩模量为E_sie=c_vier_w/k_vi (i=1,2,3）。

为使计算公式得以简化,定义5个无量纲参数：

$\begin{array}{l} a_{i} = \frac{k_{v i}}{k_{v 1}}; b_{i} = \frac{E_{s 1 e}}{E_{s i e}}; c_{i} = \frac{H_{i}}{H_{1}}; μ_{i} = \sqrt{\frac{b_{i}}{a_{i}}} (i = 1, 2, 3) ； \\ d_{i} = \sqrt{\frac{a_{i - 1} b_{i - 1}}{a_{i} b_{i}}} \begin{matrix} \end{matrix} (i = 2, 3) 。 \end{array}}$

(21)

根据谢康和^[22]的研究,容易得到：

（1）各加固区和下卧层的平均超静孔压

${\begin{cases} {\hat{u}}_{s 1} (z, t) = p \sum_{m = 1}^{\infty} C_{m} s i n (λ_{m} \frac{z}{H_{1}}) e^{- λ_{m}^{2} T_{v1e}}, \\ {\hat{u}}_{s 2} (z, t) = p \sum_{m = 1}^{\infty} C_{m} [s i n (λ_{m}) c o s (μ_{2} λ_{m} \frac{z - H_{1}}{H_{1}}) + \\ d_{2} c o s (λ_{m}) s i n (μ_{2} λ_{m} \frac{z - H_{1}}{H_{1}})] e^{- λ_{m}^{2} T_{v1e}}, \\ {\hat{u}}_{s 3} (z, t) = p \sum_{m = 1}^{\infty} \frac{C_{m} A_{m}}{c o s (μ_{3} c_{3} λ_{m})} c o s (μ_{3} λ_{m} \frac{H - z}{H_{1}}) e^{- λ_{m}^{2} T_{v1e}}, \end{cases}$

(22)

$T_{v1e} = c_{v1e} t / H_{1}^{2}$ 。

(23)

（2）桩间土和下卧层土的平均孔压

将式（14）代入式（22）,可得悬浮长芯SDCM桩复合地基上、下部加固区中桩间土和下卧层土平均超静孔隙水压力：

${\begin{cases} {\bar{u}}_{s 1} (z, t) = \frac{p}{1 - m} \sum_{m = 1}^{\infty} C_{m} s i n (λ_{m} \frac{z}{H_{1}}) e^{- λ_{m}^{2} T_{v 1 e}}, \\ {\bar{u}}_{s 2} (z, t) = \frac{p}{1 - m ρ} \sum_{m = 1}^{\infty} C_{m} [s i n (λ_{m}) c o s (μ_{2} λ_{m} \frac{z - H_{1}}{H_{1}}) + \\ d_{2} c o s (λ_{m}) s i n (μ_{2} λ_{m} \frac{z - H_{1}}{H_{1}})] e^{- λ_{m}^{2} T_{v1e}}, \\ {\bar{u}}_{s 3} (z, t) = p \sum_{m = 1}^{\infty} \frac{C_{m} A_{m}}{c o s (μ_{3} c_{3} λ_{m})} c o s (μ_{3} λ_{m} \frac{H - z}{H_{1}}) e^{- λ_{m}^{2} T_{v1e}}, \end{cases}$

(24)

$C_{m} = \frac{2 d_{2} s i n (2 μ_{3} c_{3} λ_{m})}{λ_{m} [s i n (2 μ_{3} c_{3} λ_{m}) (d_{2} + μ_{2} c_{2} F_{m}) - μ_{3} c_{3} D_{m}]}$ ,

(25)

$A_{m} = s i n (λ_{m}) c o s (μ_{2} c_{2} λ_{m}) + d_{2} c o s (λ_{m}) s i n (μ_{2} c_{2} λ_{m})$ ,

(26)

$D_{m} = s i n (2 μ_{2} c_{2} λ_{m}) E_{m} - d_{2} s i n (2 λ_{m}) c o s (μ_{2} c_{2} λ_{m})$ ,

(27)

$E_{m} = s i n^{2} (λ_{m}) - d_{2}^{2} c o s^{2} (λ_{m})$ ,

(28)

$F_{m} = s i n^{2} (λ_{m}) + d_{2}^{2} c o s^{2} (λ_{m})$ 。

(29)

按下面方程求解出特征值 $λ_{m}$ ：

$A_{m} + d_{3} c o t (μ_{3} c_{3} λ_{m}) B_{m} = 0$ ,

(30)

$B_{m} = s i n (λ_{m}) s i n (μ_{2} c_{2} λ_{m}) - d_{2} c o s (λ_{m}) c o s (μ_{2} c_{2} λ_{m})$ 。

(31)

（3）复合地基整体平均固结度

参考谢康和^[22]的研究,容易得到悬浮长芯SDCM桩复合地基按沉降定义和按孔压定义的整体平均固结度U_s和U_p的计算公式：

$U_{s} = 1 - \sum_{m = 1}^{\infty} \frac{C_{m}}{λ_{m} (1 + b_{2} c_{2} + b_{3} c_{3})} e^{- λ_{m}^{2} T_{v1e}}$ ,

(32)

$\begin{matrix} U_{p} = 1 - \sum_{m = 1}^{\infty} \frac{\sqrt{a_{2} b_{2}} B_{m} (b_{3} - b_{2}) + b_{2} b_{3} + (b_{3} - b_{2} b_{3}) c o s (λ_{m})}{λ_{m}^{} b_{2} c_{3} (1 + c_{2} + c_{3})} \cdot \\ C_{m} e^{- λ_{m}^{2} T_{v1e}} 。 \end{matrix}$

(33)

4. 算例验证

算例中,H=20 m,r_e=1.1 m；芯桩：r_sp=0.175 m,L_sp= H₁+ H₂=12 m,E_sp=20 GPa,泊松比μ_sp=0.17。搅拌桩壳：r_p=0.35 m,L_p=H₁=8 m,E_p=150 MPa,泊松比μ_p=0.25。地基土：H₃=8 m,E_s1=E_s2=3 MPa,E_s3=9 MPa,k_v1=k_v2=k_v3=10^-8 m/s,泊松比μ_s=0.35。为了在数值计算中近似模拟等应变条件,在复合地基表面铺设0.5 m厚的混凝土板,板上荷载p=68 kPa瞬时施加。混凝土板压缩模量和泊松比与芯桩相同。地基土、芯桩、搅拌桩壳和混凝土板均采用线弹性模型。在各材料的弹性模量E和压缩模量E₁之间按E= (1+ μ)(1-2μ)E₁/(1-μ)近似换算,μ为泊松比。图2为悬浮长芯SDCM桩复合地基轴对称有限元模型。模型左、右侧边界上约束径向位移,不排水。模型底边界上径向和竖向均约束,不排水。复合地基表面自由,排水。

图 2 有限元模型

Figure 2. FEM model

下载: 全尺寸图片幻灯片

采用ABAQUS有限元软件进行算例固结分析。混凝土板、芯桩和搅拌桩壳采用4结点四边形单元（CAX4）剖分,桩间土采用应力-孔压耦合4结点四边形单元（CAX4P）剖分。芯桩-土交界处设置摩擦接触对,摩擦系数取0.42。模型共剖分2466个单元,结点总数2742个。

图3给出本文解析解计算的悬浮长芯SDCM桩复合地基整体平均固结度（U_s）曲线与有限元计算结果的比较,时间轴采用无量纲时间因数T_u=c_v1t/H²。图3表明,本文解析解与有限元计算结果较为接近,解析解数值略大于数值解,二者差值最大不超过3.0%。计算表明,解析解有较高的计算精度。

图 3 解析解和有限元解的比较

Figure 3. Comparison between analytical results and FEM results

下载: 全尺寸图片幻灯片

5. 复合地基结性状分析

采用的几何和力学参数基准值如下：H=20 m,H₁=10 m,H₂=5 m,H₃=5 m。m=0.1, $ρ$ =0.25。E_p=150 MPa,E_sp=20 GPa。E_s1=E_s2=3 MPa,E_s3=9 MPa。k_v1=k_v2=k_v3=10^-8 m/s。

（1）桩的贯入比的影响

图4给出长芯SDCM桩贯入比 $β$ =L_sp/H的变化对复合地基固结速率的影响,计算时地基土为均质土,E_s3=3 MPa,搅拌桩壳长度与芯桩长度的比值 $β_{1}$ =L_p/ L_sp=0.67保持不变。图4表明,复合地基的固结速率随着长芯SDCM桩贯入比的增加逐渐增大,当 $β$ >0.75以后,复合地基固结速率的增加率显著增大。

图 4 β对固结速率的影响

Figure 4. Influences of β on consolidation rate

下载: 全尺寸图片幻灯片

（2）搅拌桩壳的刚度和几何尺寸的影响

图5～7分别给出上部SDCM桩置换率m、搅拌桩壳长度与芯桩长度之比 $β_{1}$ =L_p/L_sp和搅拌桩壳压缩模量E_p的变化对复合地基固结速率的影响。在图5固结度曲线计算中,芯桩截面积保持不变,即m_iρ_i=mρ=0.025,m越大表示搅拌桩壳的厚度越大。图5～7计算结果表明,搅拌桩壳的厚度、长度和压缩模量的变化对悬浮长芯SDCM桩复合地基的固结速率没有影响。

图 5 　m对固结速率的影响

Figure 5. Influences of m on consolidation rate

下载: 全尺寸图片幻灯片

图 6 β₁对固结速率的影响

Figure 6. Influences of β₁ on consolidation rate

下载: 全尺寸图片幻灯片

图 7 E_p对固结速率的影响

Figure 7. Influences of E_p on consolidation rate

下载: 全尺寸图片幻灯片

（3）芯桩刚度和含心率的影响

图8,9分别给出芯桩的截面含芯率 $ρ$ 和压缩模量E_sp的变化对复合地基固结速率的影响。图8表明,芯桩含芯率 $ρ$ 的变化对悬浮长芯SDCM桩复合地基固结速率近乎没有影响。当含芯率 $ρ$ 增大时,仅在固结前期复合地基的固结速率会略微减小,但降幅非常小,可以忽略不计。从图9中可见,芯桩压缩模量E_sp的变化对悬浮长芯SDCM桩复合地基前期的固结速率有一定影响。随着E_sp数值的增加,前期复合地基固结速率随之减小,但降幅并不大。总的来看,芯桩刚度的变化对复合地基固结速率的影响不大。

图 8 ρ对固结速率的影响

Figure 8. Influence of ρ on the consolidation rate

下载: 全尺寸图片幻灯片

图 9 E_sp对固结速率的影响

Figure 9. Influences of E_sp on consolidation rate

下载: 全尺寸图片幻灯片

（4）下卧层土体刚度的影响

图10给出下卧层土压缩模量E_s3取不同数值情况下悬浮长芯SDCM桩复合地基的U_s-T_u曲线。图10表明,复合地基的固结速率随下卧层土刚度的增加而增大。这说明,将芯桩的桩端置于承载力较大的持力层上可加速复合地基的固结。

图 10 E_s3对固结速率的影响

Figure 10. Influences of E_s3 on consolidation rate

下载: 全尺寸图片幻灯片

6. 结论

（1）本文固结解析解是基于加固区等竖向应变假定获得的,因此,它更适用于刚性基础下悬浮长芯SDCM桩复合地基的固结分析。

（2）桩的贯入比和下卧层土的刚度是影响悬浮长芯SDCM桩复合地基固结快慢的主要因素。桩的贯入比和下卧层土的压缩模量越大,悬浮长芯SDCM桩复合地基的固结越快。

（3）芯桩截面含芯率的变化不会影响悬浮长芯SDCM桩复合地基的固结速率。芯桩刚度的增加会略微减小固结前期复合地基的固结速率,对后期复合地基的固结速率没有影响。

（4）搅拌桩壳的厚度、长度和刚度的变化对悬浮长芯SDCM桩复合地基的固结速率没有影响。

图 1 测试装置示意图^[16]

Figure 1. Schematic diagram of testing apparatus^[16]

下载: 全尺寸图片幻灯片

图 2 扩散达到稳定状态单位面积累积溶质通量与时间关系^[31]

Figure 2. Schematic diagram of steady state diffusion results^[31]

下载: 全尺寸图片幻灯片

图 3 去离子水冲刷阶段渗滤液pH/EC随时间的变化关系

Figure 3. Variation of pH/electrical conductivity of effluent solution with time at flushing stage using DIW

下载: 全尺寸图片幻灯片

图 4 MSBS屏障试样上下两端收集液pH随时间的变化关系

Figure 4. Variation of pH in liquids collected from upper and lower ends of MSBS specimen with time

下载: 全尺寸图片幻灯片

图 5 MSBS屏障试样上下两端收集液EC随时间的变化关系

Figure 5. Variation of electrical conductivity in liquids collected from upper and lower ends of MSBS specimen with time

下载: 全尺寸图片幻灯片

图 6 MSBS屏障试样上下两端收集液中Pb²⁺浓度与时间的变化关系

Figure 6. Variation of Pb²⁺ concentration in liquids collected from upper and lower ends of MSBS specimen with time

下载: 全尺寸图片幻灯片

图 7 MSBS屏障试样上下两端化学渗透压差随时间变化关系

Figure 7. Variation of chemico-osmotic pressure of MSBS specimen with time

下载: 全尺寸图片幻灯片

图 8 试样化学渗透膜效率系数随着时间的变化

Figure 8. Change of chemico-osmotic efficiency coefficient of MSBS specimen with time

下载: 全尺寸图片幻灯片

图 9 不同岩土工程材料化学渗透膜效率系数随Pb²⁺浓度的变化

Figure 9. Relationship between chemico-osmotic efficiency coefficient and concentration of Pb²⁺ for different barrier materials

下载: 全尺寸图片幻灯片

图 10 MSBS屏障材料单位面积累计Pb²⁺质量通量Q随化学渗透时间t的关系

Figure 10. Variation of unit area accumulated quality flux of MSBS barrier specimen with time

下载: 全尺寸图片幻灯片

图 11 不同竖向阻隔材料有效扩散系数随Pb²⁺浓度的变化

Figure 11. Relationship between effective diffusion coefficient and concentration of Pb²⁺for different vertical cutoff wall backfills

下载: 全尺寸图片幻灯片

图 12 不同竖向阻隔材料阻滞因子随Pb²⁺浓度的变化

Figure 12. Relationship between retardation factor and concentration of Pb²⁺ for different cutoff wall backfills

下载: 全尺寸图片幻灯片

表 1 试验用土的基本土工参数

Table 1 Properties of soil used in this study

基本指标	天然含水率/%	重度G_s	塑限w_P/%	液限w_L/%	黏粒含量/%	粉粒含量/%	砂粒含量/%	比表面积/(m²·g^-1)	pH	蒙脱石含量/%
南京砂土	4.81	2.62	—	—	5.62	14.18	80.2	—	7.32	—
镇江膨润土	11.20	2.66	54	103	99.00	1.00	—	378.5	8.60	66.9

下载: 导出CSV

表 2 粒化高炉矿粉基本物理-化学特征

Table 2 Properties of GGBS

基本指标	数值
基本指标	GGBS	MgO
颜色	灰白色粉末	白色粉末状
含量/%	—	77.6
活性/s	—	90~100
比表面积/(m²·g^-1)	0.2564	28.0230
密度/(g·mL^-1)	—	3.58
碱度	1.871	—
pH	12.21	10.71

下载: 导出CSV

表 3 Pb(NO₃)₂污染液基本化学性质

Table 3 Basic chemical properties of Pb(NO₃)₂ liquids

溶液	Pb²⁺浓度c₀/(mg·L^-1)	EC/(μS·cm^-1)	pH
Pb(NO₃)₂	0.1	44.5	6.84
	0.5	51.6	659
	1	84.8	6.45
	2	120.1	6.31
	10	249.6	5.96
	50	487.4	5.63

下载: 导出CSV

参考文献(38)

[1]	刘松玉, 詹良通, 胡黎明, 等. 环境岩土工程研究进展[J]. 土木工程学报, 2016, 49(3): 6–30. https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201603003.htm LIU Song-yu, ZHAN Liang-tong, HU Li-ming, et al. Environmental geotechnics: state-of-the-art of theory, testing and application to practice[J]. China Civil Engineering Journal, 2016, 49(3): 6–30. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-TMGC201603003.htm
[2]	陈云敏, 谢海建, 张春华. 污染物击穿防污屏障与地下水土污染防控研究进展[J]. 水利水电科技进展, 2016, 36(1): 1–10. https://www.cnki.com.cn/Article/CJFDTOTAL-SLSD201601002.htm CHEN Yun-min, XIE Hai-jian, ZHANG Chun-hua. Review on penetration of barriers by contaminants and technologies for groundwater and soil contamination control[J]. Advances in Science and Technology of Water Resources, 2016, 36(1): 1–10. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-SLSD201601002.htm
[3]	钱学德, 朱伟, 王升位. 填埋场和污染场地防污屏障设计与施工-上册[M]. 北京: 科学出版社, 2017. QIAN Xue-de, ZHU Wei, WANG Sheng-wei. Design and Condtruction of Protective Barriers for Waste Containments and Contaminated Sites[M]. Beijing: Science Press, 2017. (in Chinese)
[4]	ROWE R, QUIGLEY R, BOOKER J. Barrier Systems for Waste Disposal Facilities[M]. London: CRC Press, 2014.
[5]	YEO S S, SHACKELFORD C D, EVANS J C. Consolidation and hydraulic conductivity of nine model soil-bentonite backfills[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2005, 131(10): 1189–1198. doi: 10.1061/(ASCE)1090-0241(2005)131:10(1189)
[6]	WAN H W, SHUI Z H, LIN Z S. Analysis of geometric characteristics of GGBS particles and their influences on cement properties[J]. Cement and Concrete Research, 2004, 34(1): 133–137. doi: 10.1016/S0008-8846(03)00252-7
[7]	LIU S H, HAN W W, LI Q. Hydration properties of ground granulated blast-furnace slag (GGBS) under different hydration environments[J]. Materials Science, 2017, 23(1): 70–77.
[8]	HAHA M B, LOTHENBACH B, SAOUT G L, et al. Influence of slag chemistry on the hydration of alkali-activated blast-furnace slag—part Ⅰ: effect of MgO[J]. Cement and Concrete Research, 2011, 41(9): 955–963. doi: 10.1016/j.cemconres.2011.05.002
[9]	YI Y L, LISKA M, AL-TABBAA A. Initial investigation into the use of GGBS-MgO in soil stabilisation[C]//Proceedings of the Fourth International Conference on Grouting and Deep Mixing. 2012. New Orleans.
[10]	伍浩良, 杜延军, 王菲, 等. 碱激发矿渣膨润土系竖向隔离墙体材料施工和易性及强度特性[J]. 东南大学学报(自然科学版), 2016, 46(增刊1): 25-30. https://www.cnki.com.cn/Article/CJFDTOTAL-DNDX2016S1005.htm WU Hao-liang, DU Yan-jun, WANG Fei, et al. Workability and strength characteristics of alkali-activated slag-bentonite backfills for vertical slurry cutoff wall[J]. Journal of Southeast University (Natural Science Edition), 2016, 46(S1): 25–30. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-DNDX2016S1005.htm
[11]	WU H L, JIN F, ZHOU A N, et al. The engineering properties and reaction mechanism of MgO-activated slag cement-clayey sand-bentonite (MSB) cutoff wall backfills[J]. Construction and Building Materials, 2021, 271: 121890. doi: 10.1016/j.conbuildmat.2020.121890
[12]	WU H L, JIN F, NI J, et al. Engineering properties of vertical cutoff walls consisting of reactive magnesia-activated slag and bentonite: workability, strength, and hydraulic conductivity[J]. Journal of Materials in Civil Engineering, 2019, 31(11): 04019263. doi: 10.1061/(ASCE)MT.1943-5533.0002908
[13]	WU H L, NI J, ZENG L, et al. Durability of alkali-activated slag-bentonite cutoff wall exposed to sodium sulfate and Pb-Zn solution[C]//The International Congress on Environmental Geotechnics, 2018, Hangzhou.
[14]	傅贤雷, 杜延军, 沈胜强, 等. PAC改性膨润土/砂竖向阻隔屏障回填料化学渗透膜效应及扩散特性研究[J]. 岩石力学与工程学报, 2020, 39(增刊2): 3669–3675. https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2020S2044.htm FU Xian-lei, DU Yan-jun, SHEN Sheng-qiang, et al. Chemico-osmotic membrane behavior and diffusive properties of PAC amended bentonite/sand vertical cutoff wall backfills[J]. Chinese Journal of Rock Mechanics and Engineering, 2020, 39(S2): 3669–3675. (in Chinese) https://www.cnki.com.cn/Article/CJFDTOTAL-YSLX2020S2044.htm
[15]	傅贤雷, 张润, 万勇, 等. 改性土–膨润土阻隔屏障化学渗透膜效应研究[J]. 岩土工程学报, 2020, 42(增刊1): 172–176. doi: 10.11779/CJGE2020S1034 FU Xian-lei, ZHANG Run, WAN Yong, et al. Chemico-osmotic membrane behaviors of amended soil-bentonite vertical barrier[J]. Chinese Journal of Geotechnical Engineering, 2020, 42(S1): 172–176. (in Chinese) doi: 10.11779/CJGE2020S1034
[16]	FU X L, ZHANG R, REDDY K R, et al. Membrane behavior and diffusion properties of sand/SHMP-amended bentonite vertical cutoff wall backfill exposed to lead contamination[J]. Engineering Geology, 2021, 284: 106037. doi: 10.1016/j.enggeo.2021.106037
[17]	SCALIA J IV, BOHNHOFF G L, SHACKELFORD C D, et al. Enhanced bentonites for containment of inorganic waste leachates by GCLs[J]. Geosynthetics International, 2018, 25(4): 392–411. doi: 10.1680/jgein.18.00024
[18]	MITCHELL J K, SOGA K. Fundamentals of Soil Behavior[M]. New York: John Wiley & Sons, 2005.
[19]	SHACKELFORD C D, LEE J M. The destructive role of diffusion on clay membrane behavior[J]. Clays and Clay Minerals, 2003, 51(2): 186–196. doi: 10.1346/CCMN.2003.0510209
[20]	肖承坤. 我国铅污染现状分析[C]//全国铅污染监测与控制治理技术交流研讨会, 2007, 上海. XIAO Cheng-kun. Analysis of present situation about lead pollution in China[C]//National Lead Pollution Monitoring and Control Technology Exchange Seminar, 2007, Shanghai. (in Chinese)
[21]	地下水环境质量标准: GB/T14848—2017[S]. 2017. Environmental Quality Standard for Groundwater: GB/T14848—2017[S]. 2017. (in Chinese)
[22]	Standard Test Method for Electrical Conductivity and Resistivity of Water: ASTM D1125—14[S]. 2014.
[23]	Method for pH of Aqueous Solutions with the Glass Electrode: ASTM E70-07[S]. 2015.
[24]	FRITZ S J. Ideality of clay membranes in osmotic processes: a review[J]. Clays and Clay Minerals, 1986, 34(2): 214–223. doi: 10.1346/CCMN.1986.0340212
[25]	MALUSIS M A, SHACKELFORD C D. Chemico-osmotic efficiency of a geosynthetic clay liner[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2002, 128(2): 97–106. doi: 10.1061/(ASCE)1090-0241(2002)128:2(97)
[26]	KANG J B, SHACKELFORD C D. Clay membrane testing using a flexible-wall cell under closed-system boundary conditions[J]. Applied Clay Science, 2009, 44(1/2): 43–58.
[27]	YE W M, SU W, CHEN Y G, et al. Membrane behavior of compacted GMZ bentonite and its granite mixture[J]. Environmental Earth Sciences, 2017, 76(20): 1–13.
[28]	MALUSIS M A, SHACKELFORD C D, OLSEN H W. A laboratory apparatus to measure chemico-osmotic efficiency coefficients for clay soils[J]. Geotechnical Testing Journal, 2001, 24(3): 229–242. doi: 10.1520/GTJ11343J
[29]	HENNING J T, EVANS J C, SHACKELFORD C D. Membrane behavior of two backfills from field-constructed soil-bentonite cutoff walls[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2006, 132(10): 1243–1249. doi: 10.1061/(ASCE)1090-0241(2006)132:10(1243)
[30]	SHACKELFORD C D. Laboratory diffusion testing for waste disposal—A review[J]. Journal of Contaminant Hydrology, 1991, 7(3): 177–217. doi: 10.1016/0169-7722(91)90028-Y
[31]	陈左波. 砂-膨润土系竖向隔离墙阻滞重金属污染物运移特性的试验研究[D]. 南京: 东南大学, 2014. CHEN Zuo-bo. Research of Limiting Migration of Heavy Metal of Sand. Bentonite Vertical Cutoff Wall[D]. Nanjing: Southeast University, 2017. (in Chinese)
[32]	SHACKELFORD C D. Membrane behavior in geosynthetic clay liners[C]//Geo-Frontiers Congress, 2011, Dallas.
[33]	梅丹兵. 土–膨润土系竖向隔离工程屏障阻滞污染物运移的模型试验研究[D]. 南京: 东南大学, 2017. MEI Dan-bing. Model Test Study of Limiting Migration of HeavyMeal of Soil-Bentonite Vertical Cutoff Wall[D]. Nanjing: Southeast University, 2017. (in Chinese)
[34]	张润. 六偏磷酸钠改良膨润土系竖向工程屏障防渗吸附扩散性能研究[D]. 南京: 东南大学, 2018. ZHANG Run. Hydraulic and Containment Performance of Shmp-Amended Soil-Bentonite Vertical Cutoff Wall Backfills Against Heavy Metals[D]. Nanjing: Southeast University, 2018. (in Chinese)
[35]	TANG Q. Factors Affecting Waste Leachate Generation and Barrier Performance of Landfill Liners[D]. Tokyo: University of Tokyo. 2013.
[36]	SHACKELFORD C. Membrane behavior in engineered bentonite-based containment barriers[M]//Coupled Phenomena in Environmental Geotechnics. London: CRC Press, 2013.
[37]	CONSOLI N C, HEINECK K S, CARRARO J A H. Portland cement stabilization of soil–bentonite for vertical cutoff walls against diesel oil contaminant[J]. Geotechnical and Geological Engineering, 2010, 28(4): 361-371. doi: 10.1007/s10706-009-9297-5
[38]	OWAIDAT L M, ANDROMALOS K B, SISLEY J L, et al. Construction of a soil-cement-bentonite slurry wall for a levee strengthening program[C]//Proceedings of the 1999 Annual Conference of the Association of State Dam Safety Officials, 1999. St Louis.

施引文献

资源附件(0)

图(12) / 表(3)

计量

文章访问数: 226
HTML全文浏览量: 33
PDF下载量: 130
被引次数: 0

0. 引言
1. 固结模型与基本假定
1.1 轴对称固结模型
1.2 基本假定
2. 固结方程与定解条件
2.1 固结方程
2.2 定解条件
3. 固结解析解
3.1 方程与定解条件的函数变换
3.2 固结解析解
4. 算例验证
5. 复合地基结性状分析
6. 结论

氧化镁碱激发矿粉-膨润土-土竖向屏障材料阻隔铅污染物的化学渗透膜效应 English Version

作者简介: 李双杰(1997—)，男，硕士研究生，主要从事环境岩土工程学习和研究。E-mail: 220193046@seu.edu.cn

通讯作者: 杜延军, E-mail: duyanjun@seu.edu.cn

计量

出版历程

Experimental study on chemico-osmotic membrane behaviors of reactive MgO-activated slag-bentonite backfill in vertical cutoff walls exposed to Pb-laden groundwater

0. 引言

1. 固结模型与基本假定

1.1 轴对称固结模型

1.2 基本假定

2. 固结方程与定解条件

2.1 固结方程

2.2 定解条件

3. 固结解析解

3.1 方程与定解条件的函数变换

3.2 固结解析解

4. 算例验证

5. 复合地基结性状分析

6. 结论

计量

出版历程

目录

0. 引言

1. 固结模型与基本假定

1.1 轴对称固结模型

1.2 基本假定

2. 固结方程与定解条件

2.1 固结方程

2.2 定解条件

3. 固结解析解

3.1 方程与定解条件的函数变换

3.2 固结解析解

4. 算例验证

5. 复合地基结性状分析

6. 结论

作者简介:
李双杰(1997—)，男，硕士研究生，主要从事环境岩土工程学习和研究。E-mail: 220193046@seu.edu.cn

通讯作者:
杜延军, E-mail: duyanjun@seu.edu.cn