白水河大桥场区黄土地基湿陷性分析

以白水河大桥施工场地黄土地层为研究对象,分析场地黄土的湿陷系数、自重失陷系数与深度的关系,湿陷量、自重湿陷量与深度的关系,研究得出场区的黄土湿陷特点:研究区地貌单元属河谷阶地区,地处阶地前缘斜坡处,发生湿陷的地层为上更新统风积黄土、古土壤及中更新统风积黄土层。湿陷性黄土主要有轻矿物、重矿物和粘土矿物组成。黄土的化学组成主要为SiO_2,其次为Al_2O_3,Fe_2O_3和CaO等,但黄土湿陷性的发生与黄土的矿物组成及化学组成关系较小。综合分析研究区黄土湿陷性影响因素,认为湿陷性主要影响因素为含水状态,应力状态等。对比分析湿陷系数,湿陷量随深度的变化规律:随着计算深度的增加,湿陷量、湿陷系数均呈先增加后减少趋势。最终判定研究区地基湿陷等级为Ⅲ级,为严重湿陷。该研究成果对工程建设中遇到的黄土湿陷的分析及其治理具有重要意义。     

西宁地区湿陷性黄土状土层的工程特性及地基处理探讨

西宁地区黄土层分布较为广泛,本文主要利用近几年工程实际资料,对西宁地区高阶地的黄土状土层的试验数据进行了大量统计分析,通过分析研究对该地区黄土的工程特性和处理方法有了初步的认识.本文就该地区黄土的分布和时代成因、湿陷性、湿陷规律、工程特性、处理方法、工程中遇到的问题等做了分析总结,得出了一些规律,对工程实践有一定的指导意义.     

陕西彬县地区湿陷性黄土纵向分布特征及湿陷性计算

通过对陕西彬县地区黄土进行物性指标及湿陷性试验,探讨了该地区物理性质指标及湿陷性的纵向分布规律,根据分布特征结合数理统计的方法对湿陷性的关键因素进行研究,拟合其相应经验公式,进一步总结出该地区黄土的一些特征,对该地区黄土的研究及工程勘察设计提供参考依据。     

湿陷性黄土地区海绵城市建设研究进展

海绵城市作为城市雨洪管理、人居环境改善的重要手段,在水资源、水环境及水灾害问题突出的湿陷性黄土地区开展具有现实意义.为保证湿陷性黄土地区海绵城市建设的有效性与安全性,通过梳理黄土水分入渗规律、湿陷机理及湿陷性黄土地区海绵城市建设的研究趋势和不足,总结了湿陷性黄土地区海绵城市安全有效推进所面临的问题主要有:海绵城市建设需...     

浅谈湿陷性黄土地基处理方法

本文分析研究了湿陷性黄土地基处理方法的重要性,指出湿陷性黄土处理的基本原则,对比研究各种地基处理方法的适用情况及优缺点,并结合工程实例进行了论证。     

强夯处理湿陷性黄土地基效果浅析

强夯是处理湿陷性黄土地基的一种有效方法。灵宝市委市政府办公大楼湿陷性黄土地基，经强夯处理后，地基土孔隙比和压缩系数降低，干密度提高，湿陷性被消除，地基承载力大幅度提高并满足了建筑设计基础底面压力２２０ｋＰａ／ｍ２的要求。     

用素土桩挤密法处理陇东湿陷性黄土地基

素土桩挤密地基由桩间挤密土和回填素土夯实的桩体组成，它是一种人工“复合地基”。其作用是通过素土桩挤密法提高地基土的密实度，从而对湿陷性黄土达到消除浅部或深部的部分或全部湿陷性的作用，并改善地基承载能力，减少地基变形。本文通过现场单桩、群桩单元体轻便触探、小环刀深层取样、开剖取样等方法对场地地基土挤密前、后干重度和压实系数进行了对比分析，判定用素土桩挤密法处理陇东湿陷性黄土地基的可行性。     

黄土路基降雨入渗现场试验

为了寻求适合黄土地区公路路基湿陷性评价的方法,找到符合公路工况的实际水分入渗规律,通过现场人工降雨试验,观测了湿陷性黄土路基在百年一遇降雨强度下的入渗以及饱和深度,并结合有限元数值模拟,分析了湿陷性黄土降雨入渗的规律.结果表明:在降雨条件下湿陷性黄土路基入渗的影响深度小于2.7 m,饱和深度为20 cm.该结果可为黄土地区路基处理设计中的黄土湿陷性评价、施工提供依据.     

模糊评判法在公路黄土洞穴发育程度分区中的应用

阐述了影响黄土洞穴形成的黄土湿陷性、崩解性、地质构造、节理裂隙、微地形地貌和水文及气候条件等工程地质特性和地质因素;在公路沿线地区,公路工程质量及人类活动也是黄土洞穴形成的影响因素。洞穴发育程度分区预测和评价极具复杂性、随机性和模糊性,为此,在对各影响因素分析的基础上,借助模糊综合评判法,对黄土区公路沿线洞穴发育程度分区进行了研究。与实际情况对比分析表明,预测评价结果合理可靠,可作为黄土区已建公路洞穴灾害的防治依据。     

关中地区饱和黄土工程地质特性

关中地区广泛分布着黄土地层,当地下水埋深较浅时,湿陷性黄土往往由于地下水的作用,常呈饱和状态的非湿陷性黄土,简称饱和黄土. 当该土层若作建筑物地基(持力层或下卧层)被利用时,就必须掌握其基本性质和工程特性. 根据关中地区部分饱和黄土资料,分析和论证了关中地区饱和黄土的基本物理力学性质和工程特性,目的为了正确合理地利用饱和黄土地基取得效益.     

西宁的黄土研究

根据古地磁、磁化率、粒度和重矿物分析及电镜扫描石英砂表面特征等测试手段的综合研究,西宁地区的黄土可分出从S_0至L_(17)的连续黄土——古土壤序列。它包括全新世黄土、马兰黄土、离石黄土和午城黄土,形成的时间为1.2MaB·P.。黄土粒度粗,且含有两个风成细砂分层。重矿物以不透明矿物、角闪石为主,次为绿泥石、锆石和金红石等。石英砂颗粒以次棱角状为主,其次为棱角状。石英砂表面机械结构中有众多的冰川作用痕迹和风力作用痕迹。本区黄土主要来源于青藏高原第四纪局部冰盖、冰川及其外围广大冰缘地区所产生的粉砂物质。西宁大墩岭黄土剖面详细地记录了1.2MaB·P.的环境变化信息。其中1.1MaB·P.形成的L_(15)顶部的细砂分层代表1.2Ma以来最为干冷的严酷时期。L_1和L_2是末次冰期和倒数第二次冰期的产物。倒数第二次冰期比末次冰期更为干冷,极盛时期为0.155MaB·P.。S_1S_3和S_4可能代表1.2Ma以来本区最为温暖湿润的时期。     

西宁地区次生盐渍土的分布特征及地基处理方法

西宁地区次生盐渍土主要分布于山麓斜坡带高阶地和河谷高漫滩,前者属中～弱硫酸、亚硫酸盐渍土,且多具中等～强烈湿陷性,盐份主要来自斜坡后缘含盐碎屑岩风化物及易溶盐;后者为中等亚氯、亚硫酸盐渍土,溶于土中的盐份系浅层咸地下水常年毛细上升蒸发所致。其次生盐渍土的松胀性、溶陷性、腐蚀性较强,工程建设要引起重视。     

Influences of soil moisture and salt content on loess shear strength in the Xining Basin,northeastern Qinghai-Tibet Plateau

Moisture and salt content of soil are the two predominant factors influencing its shear strength. This study aims to investigate the effects of these two factors on shear strength behavior of loess in the Xining Basin of Northeast Qinghai-Tibet Plateau, where such geological hazards as soil erosion, landslides collapse and debris flows are widespread due to the highly erodible loess. Salinized loess soil collected from the test site was desalinized through salt-leaching in the laboratory. The desalinized and oven-dried loess samples were also artificially moisturized and salinized in order to examine how soil salinity affects its shear strength at different moisture levels. Soil samples prepared in different ways(moisturizing, salt-leaching, and salinized) were measured to determine soil cohesion and internal friction angle. The results show that salt-leaching up to 18 rounds almost completely removed the salt content and considerably changed the physical components of loess, but the soil type remained unchanged. As salt content increases from 0.00% to 12.00%, both the cohesion and internal friction angle exhibit an initial decrease and then increase with salt content. As moisture content is 12.00%, the salt content threshold value for both cohesion and internal friction angle is identified as 3.00%. As the moisture content rises to 16.0% and 20.00%, the salt content threshold value for cohesion is still 6.00%, but 3.00% for internal friction angle. At these thresholds soil shear strength is the lowest, below which it is inversely related to soil salinity. Beyond the thresholds, however, the relationship is positive. Dissimilar to salinity, soil moisture content exerts an adverse effect on shear strength of loess. The findings of this study can provide a valuable guidance on stabilizing the engineering properties of salinized loess to prevent slope failures during heavy rainfall events.     

Microstructure evolution of loess under multiple collapsibility based on nuclear magnetic resonance and scanning electron microscopy

In recent years, the acceleration of urbanization in loess areas has prompted frequent dismantling and reconstruction of old urban areas. Demolition and reconstruction of buildings involve multiple collapses of the foundation. To study microstructure evolution of loess under multiple collapsibility, this paper selects undisturbed loess samples from Guyuan, Northwest China for multiple compression tests. Using nuclear magnetic resonance(NMR) imaging and scanning electron microscopy(SEM) as auxiliary methods, a combination of qualitative and quantitative analyses was used to study the microstructure of loess samples before and after various number of collapses under different pressures. Results show that the loess does undergo multiple collapse under 200 kPa pressure. Pore is an important reason for loess collapse. The initial collapse comes primarily from the compression of macropores and mesopores, and the second collapse comes primarily from mesopore compression. The compression process of loess can be roughly divided into two stages. First, under the action of dissolution and compression, the relative displacement of soil particles occurs. Macropores and mesopores are destroyed first, generating small pores. Second, with increasing pressure and times of collapses, pore compression gradually transforms into small pore compression. During the first collapse, particle aggregates disintegrate due to water and pressure. However, with increasing times of collapses, the contact relationship between particles gradually changes from the point contact to face contact. Loess particles tend to gradually become rounded. The study of the microstructure provides the possibility to further reveal the mechanism of multiple collapsibility of loess.     

关于黄土含水量划分的讨论

黄土含水量高低,通常能反映出黄土中含水量的变化规律和土性特点。本文对黄土含水量高低的划分和命名做了初步尝试,并对其划分和命名所考虑的因素和依据做了简要讨论。     

西宁盆地泥质型钙芒硝资源的开发利用

西宁盆地蕴藏着极为丰富的钙芒硝资源,80年代即已探明硫酸钠(Na_2SO_4)地质储量20亿吨,远景储量100亿吨以上。矿床所在地距西宁市区2～10余km,水、电、路“三通”良好,且无水硫酸钠及其深加工产品市场颇为广阔。80年代以来,这种“城市矿”曾几次建厂开发。至今未能开发成功的直接原因是,矿石含泥质物较高,用常规方法脱除困难。笔者以新的工艺流程进行的日产10吨芒硝的脱泥除杂中试试验表明,以这种泥质型矿为原料,完全可以以低的成本生产出高纯度的硫酸钠产品,可以取得可观的经济效益。西宁盆地具备形成一个硫酸钠盐型盐化工工业基地的基本条件。     

Experimental study on improving collapsible loess with cement

The collapsibility of loess ground can directly affect stability of subgrade. Therefore, how to adopt practical technical measures to reduce or eliminate its collapse deformation is an important content in foundation design in collapsible loess zone. Selecting collapsible loess from Fuxin-Chaoyang highway in Liaoning, the authors conducted a series of tests for improving loess with cement. The loess in different water content was mixed with the cement in varying proportions, unconfined compression strength for the samples at four different curing periods were tested, and the relationships of improved soil strength among cement mixture ratio and curing periods were analyzed. When the curing periods are certain, the strength of loess increases along with the mixture ratio increases; when the cement mixture ratio is 5%-15%, the scope of increases is quite obvious; when the mixture ratio is greater than 15%, the tendency of intensity increases turns slow. When the mixture ratio for the specimen is certain, the intensity of the test specimen increases along with the curing period increases, the intensity grows obviously in 28 days, and the growth rate is small in 28-90 days, the intensity tends to be steady in the curing period of 90 days.