【Objective】 Environmental contamination by heavy metals is ubiquitous in many ecosystems. In this paper, we assess heavy metal pollution in sediments of the irrigation canals in the Xiangjiang River basin, as well as their ecological risks. 【Method】 Taking Lei Shui region, an important tributary of the Xiangjiang River, as an example, we analyzed the total contents of As, Cd, Cr, Cu, Ni, Pb and Zn, as well as their water-soluble forms in sediments of the irrigation canals. The geo-accumulation index method and ecological risk coefficient/index method were used to evaluate sediment contamination and its ecological risk. Correlation analysis and principal component analysis were used to elucidate the origin of the heavy metals found in the sediments. 【Result】 The sediments in the irrigation canals in the studied region were severely polluted, with a particularly notable concentration of Cd contamination. The total content of heavy metals in the sediments was 6.4 times the background value, predominantly caused by anthropogenic activities. Ecological risk in the area is hence high, especially the risk of Cd followed by As. The accumulation of As-Cd-Zn and Pb-Cu in the sediments was due to industrial and mining activities, respectively, while Ni, Cr and accumulation of As-Cd-Zn and Pb-Cu was caused by both industrial and mining activities. Ni and Cr in the sediments were naturally originated. 【Conclusion】 The sediments in the irrigation canals in the studied region were severely polluted, with Cd content pronouncedly high exceeding the geological background level by 6.4-fold. Such contamination was predominantly caused by anthropogenic activities. In terms of the ecological risk, Cd was most significant followed by As. The accumulation of As-Cd-Zn and Pb-Cu in the sediments emanated from industrial and mining activities. In contrast, Ni and Cr are naturally originated.

染料废水常具有高浓度、高色度、成分复杂、难降解、难生化等特点,一直是废水处理的难点.被染料废水污染的地下水,由于其治理修复受到地质与水文地质条件的影响,其修复难度较大.近年来,可渗透反应墙(permeable reactive barrier,PRB)技术是目前迅速发展的一种原位修复技术.本研究以染料废水污染的地下水为研究对象,通过室内试验进行了PRB墙填料的筛选与配比试验,最终确定活性炭的添加比例为0.5‰～1‰的质量配比,铁粉的添加比例为489％的质量比,在此基础上,进行了可渗透性反应墙参数设计.

The solidification/stabilization method is widely used in the control of heavy metal pollution, but the high cement content will cause the defects such as high volume increase ratio and easy to produce cracks. The effect of cement, cement plus phosphate-based agent A and cement plus organic chelating agent B on the solidification/stabilization of lead-zinc waste stone and tailings was studied. The result showed that the heavy metal leaching concentration of waste stone and tailings could meet “Integrated wastewater discharge standard”（GB 8978-1996） when using appropriate amount cement, cement plus phosphate-based agent A or cement plus organic chelating agent B. However, considering the removal rate, volume increase ratio and remediation cost, the optimal agent adding scheme was 5%（mass fraction, the same below）-10% cement plus 1%-2% phosphate-based agent A,and the solidification/stabilization agent cost of this scheme was 53-114 yuan/t.

非正规垃圾堆放点治理是当前我国环境治理的重要任务,近年来其治理技术也正从简单封场、搬迁等粗放式治理向筛分综合利用等精细化治理方向转变.其中,垃圾质量及筛分产物比例参数直接影响筛分综合利用治理方案编制的合理性与投资估算的准确性.然而利用钻孔采集垃圾样品筛分的传统方法因量少而存在密度及筛分产物比例数据代表性不足的问题.本研究依托北京市大兴区9处非正规垃圾堆放点垃圾质量勘测项目,首次开展了现场混合垃圾中试筛分试验与密度试验,精准测算了垃圾质量及筛分产物(轻质筛上物、无机骨料和腐殖土)质量比例;同时针对9处堆放点现场试验成果进行统计分析,提出了两类混合垃圾堆体密度及筛分产物比例的参考范围:含生活垃圾较多的第1类混合垃圾堆体平均密度为0.534～0.750 t/m3,轻质筛上物比例为4.00％～12.90％;以建筑垃圾为主的第2类混合垃圾堆体的平均密度为1.254～1.301 t/m3,轻质筛上物比例为1.04％～2.10％.

以北方地区典型一般透水型含水层介质为研究对象,通过试验获取了垃圾渗滤液特征污染物COD和氨氮在含水层介质中的吸附系数,研究了含水层介质粒径大小、有机质含量和污染物化学特性对吸附能力的影响.结果 表明:场地典型含水层介质对COD的吸附系数为0.32～5.87 L/kg,对氨氮的吸附系数为3.05～5.97 L/kg;含水层介质对COD和氨氮的吸附曲线均符合线性等温吸附曲线;含水层介质粒径大小与其对COD和氨氮的吸附能力均成正比;含水层介质的有机碳含量与其对COD的吸附能力成正比,但对氨氮吸附能力影响不显著;氨氮在含水层介质中的自然吸附衰减作用较COD强,即氨氮在含水层中的迁移性低于COD.

A hydroponic experiment was conducted to study the interaction of Cd and Zn affecting the root morphology and accumulation of Cd and Zn in Sedum aizoon. The results show that S. aizoon exhibits a high tolerance to single stress of Cd and Zn and the concentrations of Cd and Zn in the leaf, stem, and root of S. aizoon increase as the stress levels increase. A strong phytoextraction capacity in S. aizoon was also observed for the Cd concentration in the aboveground part reaching 133.0 mg·kg-1. The combined stress of Cd and Zn has a greater effect on the growth of S. aizoon than single stress to which the root is more sensitive. The root length, surface area, root volume, and tips significantly decrease under combined stress of Cd and Zn; the effect on the tips is most significant. The low-level Zn application (10 mg·L-1) has a synergistic effect on the Cd accumulation in the shoot of S. aizoon because of the promotion of Cd translocation from root to shoot. However, the addition of Cd leads to a notable antagonism of the Zn absorption of S. aizoon. The concentration ratio of Zn and Cd also has a significant effect on the Cd uptake of S. aizoon. A high ratio promotes the Cd accumulation in the shoot, while the latter is inhibited by a low Zn/Cd ratio. Therefore, S. aizoon possesses a strong potential of Cd phytoextraction and can be applied for phytoremediation of Cd-contaminated soil, while the adjustment of the ratio of Cd and Zn in the growth medium will help to enhance the phytoremediation efficiency of S. aizoon.

为筛选出富集Cd能力较强的向日葵品种,本研究采用田间原位试验,在北方典型Cd污染农田土壤(含Cd 2.22mg/kg)上,研究了28个不同向日葵品种的生长响应和富集Cd能力的差异.结果表明,不同向日葵品种地上部生物量在1 101.38～12 511.13kg/hm2,地上部Cd含量在1.68～19.25mg/kg,生物富集系数(BCF)在0.76～8.67,地上部Cd提取量在4.17～114.20g/hm2,均表现出较大差异.通过对向日葵地上部Cd含量的聚类分析可将28个向日葵品种分为3类,并筛选出G3、G1、Y1、G8、G12、G4、G6等品种为高富集Cd型向日葵品种.对向日葵地上部Cd提取量的分析结果表明,Y3、G24和G3品种地上部Cd提取量均达100g/hm2以上,是修复Cd污染农田土壤较合适的品种.

通过接触面的自身状况和摩擦学中的粘滑现象分析,研究了边坡失稳的内在机制。引入弹簧-滑块组成的边坡演化模型,借助于数值模型结果分析了边坡变形稳定性问题,指出边坡的变形特性与岩桥的级别和数量密切相关,当其结构比较简单时,边坡的变形与时间背景图像比较清晰。

Influence of foundation excavation on nearby underground pipeline is a key problem relating safe and economic construction of city foundation,which is a difficult and hot research subject.Based on the elastic foundation beam theory proposed by the predecessors,the calculation method based on field test ground subsidence curve of calculating the influence of deep excavation on nearby underground pipeline was proposed.This method made up the shortage of supposing the ground subsidence curve above underground pipeline to be parabola,which made the calculation result more accurate.Finally,the solution process of this method was illustrated through an engineering example.The vertical displacement equation of underground pipeline was obtained,and its value solution was solved with Matlab software,which was in good agreement with that of field test.

Aiming at the actual engineering problem of influence of foundation pit excavation on underground pipelines nearby, basing on elastic foundation beam theory, the calculation method based on field test ground settlement curve of calculating the influence of foundation pit excavation on underground pipeline nearby is proposed. This method makes up the shortage of supposing the ground settlement curve above underground pipeline to be parabola, which makes the calculation result more accurate. Finally, the solution process of this method is illustrated through an engineering example. The vertical displacement equation of underground pipeline is obtained, and its value solution is solved with Matlab software, which is in good agreement with that of field test.

The established method of Herle and Kolymbas's (HK's) clay hypoplastic constitutive model is described. Several shortcomings of HK model are listed in detail by analyzing clay behavior and response envelope line; then three parameters in HK equation are modified to develop a modified HK hypoplastic formulation and determine parameters. The modified model has advantage of a few parameters which are easy to determine and a simple formulation. Meanwhile, modified HK model not only are based on rigorous mathematics and mechanics, but can be applied to practice.

The deformation stability of rock test system is studied based on rigidity criterion and nonlinear catastrophe theory.The rock deformation stability is dependent on the environment rigidity and the equivalent rigidity of rock.The rock instability occurs at a position after the peak value in the constitutive curve.An increase in the environment rigidity will be beneficial to the system stability and rigid loading will generally not lead to a strong instability-caused destruction.The formula for the deformation value corresponding to the instability position of the test system is found based on the cusp catastrophe model and rigidity criterion.

According to the characteristics of loess subsidence, the external factors such as water content and load and internal factors such as microstructure and mechanics features are analyzed. Deformation mechanism of loess subsidence is deeply researched according to the theory of microstructure un-stability. It is found that the primary causes of loess subsidence are changes of forces on the microstructure and water content after soaking, Through the analysis, it is discovered that steadily of microstructure model has enormous relatedness with the stiffness K and force state (sigma,tau) of the model. When the connection rigidity reduces, the structure loses its steadily.

Regarding the Burridge-Knopof (B-K) spring block model as a conceptual model for the physics of earthquakes has attracted much attention among physicists and seismologists. In this paper, the B-K model is used to analyze the slope instability. There are certain characteristics of the B-K model such as deterministic chaos, self-organization, etc., which provide heuristic clues to understanding of the nature of sliding slope and shed light on the instability of slope prediction.

分析了软弱带介质与上部岩体的联系,提出了弹簧-滑块模型。用突变论建立了斜坡沿单软弱结构面滑动的尖点突变模型。通过研究发现,斜坡失稳主要取决于软弱面上应变硬化介质及上部岩体与应变软化介质在应变软化曲线拐点处的刚度比k、材料的均匀性指标m及几何-力学参数,其失稳演化过程与地质环境因素变化密切相关。

对顺层边坡的溃屈进行研究,分析了挠度变化、轴向变形,并在力学机制上建立基于拱效应的失稳尖点突变模型,得出以下结论:顺层滑坡的溃屈是突然发生的,可以用尖点突变模型来描述;结构初始几何特性的无量纲参数范围在-0.863～0.463之间时,这种已经形成拱效应的顺层边坡处于稳定状态.

How to build the three dimensional model of the geologic body quickly and truly is a difficult problem which lies in the front of the numerical simulation operators. Although the three-dimensional (3D) geoscience simulation software has good 3D geological modelling ability, it can be difficult to join the corresponding geological model established by 3D study simulation software with numerical simulation software because of the difference in data structures. A majority of CAD software have good data connection with the present numerical analysis software. This paper presents a study on how to use CAD software to establish 3D geological model for 3D visualization and numerical simulation purposes. The 3D modeling of some highway slopes in Yunnan is used an examples to illustrate this approach is convenient, accurate and reasonable.

Pre-stressed anchor has been widely used in the foundation pit retaining projects. However, no much research is done on stress loss of the pre-stressed anchor, when the anchor is locked, especially, when retaining wall is a soil slope. It is concluded by field monitoring data that the load variation with time can be described as three phases.

On the basis of discussing the soil constitutive model and link model of pile and anchor in FLAC~(3D),the numerical simulation method is adopted to analyze the stability of the foundation pit after partly demolition of the original support structure.The simulation results show that the maximal horizontal displacement reaches 2.58cm,nearly 1.5 times that of the sixth and seventh conditions after demolition of the anchorage end of the third and fourth layer bolts.The axial force of the second layer bolt increases greatly and the maximal value reaches 4.13e5N,which is 2.3 times that of the sixth and seventh conditions and 1.9 times that of the design.The maximal moment of the pile reaches 8.0N·m,which is almost 3.0 times that of the sixth and seventh conditions.Therefore,it can be considered that it is very dangerous to directly demolish the two layers bolts without adding any other supporting measures.

A coattail catastrophe model is presented.The necessary and sufficient conditions leading to slope failure are discussed.The sliding belt is assumed to be planar.The sliding belt and the upside crag body are composed of the different materials with different mechanical properties.The upside crag body is modeled as the elastic brittle material(called medium 1);the sliding belt medium is modeled as a strain-softening material(called medium 2).The shear stress-strain constitutive model is described by the Weibull's distribution law.In this way,a coattail catastrophe model is developed for the slope failures.Through the analysis,it is discovered that the slope steadily has a good relation with the stiffness ratio λ of medium 1 to medium 2.Along with λ increase,the ξ_0 value that slope starts to skid reduces,and the value ξ~* of skips also reduces.At the same time,the marginal value x~* increases,and the skip quantitative Δx changes to be smaller.