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1.
全风化花岗岩地层稳定性差、遇水易发生崩解,工程上使用常规材料防渗加固注浆时效果较差。针对这一情况,依托湖南省郴州市莽山水库防渗加固灌浆项目,通过自主设计的全风化花岗岩地层注浆室内模拟试验装置,进行模拟注浆试验,实现了浆液在整个注浆过程中的扩散情况模拟,对不同注浆压力、不同位置点所取试样开展单轴抗压、抗剪强度及渗透率测试试验,对不同注浆压力下完整结石体取样观察,研究以全风化花岗岩颗粒为配方主体材料的高固相离析浆液在全风化花岗岩地层的防渗加固效果及浆液扩散模式。结果表明:该浆液在全风化花岗岩地层扩散过程中经历了渗透扩散、挤密压缩、劈裂扩展三个阶段,是一种复合注浆形式;以全风化花岗岩颗粒为主体的高固相离析浆液在全风化花岗岩地层注浆中效果显著,随着注浆压力提升,单轴抗压强度显著提升为原土体的3.25～13.67倍,抗剪强度在不同法向压力情况下提升为原土体的1.63～2.69倍,渗透系数从10?4 cm/s下降至10?5 cm/s甚至10?6 cm/s。 相似文献
2.
工程中使用水泥石灰等材料加固淤泥质土,由于土中的腐植酸有机质会阻碍水泥胶凝物质的形成,影响加固土长期强度。利用生物酶加固能够有效减小受有机质影响,但加固的时效特征却并不清晰。为探究生物酶固化剂加固淤泥质土的物性指标随时间变化规律,选择两种生物酶加固剂（泰然酶、E3酶）作为研究对象,开展加固土样的不排水不固结三轴剪切试验、光学显微与电镜扫描结合的细观结构测试等进行试验分析,研究结果表明:掺入两类生物酶以及各自改良配方后,土试样抗剪强度相较原状土最低各自提升了316.2%与287.3%。细观结构上泰然酶改良土体形成了板片状的致密结构,通过提高原土体内摩擦角达到增加抗剪强度,E3酶改良土表面则形成不规整的类球状或团聚状结构,强化了颗粒间的黏结作用,提高黏聚力以达到加固的目的。同时生物酶的效能发挥在时间尺度上为非单调增长,从第7天开始生物酶加固土样强度相较空白对照组具有优势,到60天强度逐步接近空白对照组,其作用效果存在明显的强化期（7~60 d）和衰落期（60~90 d）。研究成果对生物酶加固淤泥质土的工程问题解决具有较好的应用价值和理论意义。 相似文献
3.
《福建地质》2020,(2)
花岗岩风化残积土作为一种特殊的土体类型,保留了母岩的部分结构构造特征,由于矿物成分的风化,使其具有部分黏土的工程特征,有部分砂砾土的工程特征。依托福州市鼓楼区榕发—乌山郡筑路机械厂地块岩土工程勘察,对场区内花岗岩残积土的物理力学性质进行分析,并采取室内三轴试验和原位测试的方法对其工程特性进行研究。研究表明场地内花岗岩残积土在风化过程中,仍保留了母岩的部分构造特征,增强了花岗岩残积土受外荷载时的抗变形能力;长石等矿物风化成的次生矿物主要为高岭土,对花岗岩的粗颗粒具有一定的胶结作用,加强了颗粒间的结合度,使其抗剪强度有所增加。场区内标贯试验表明,随着深度的增加,标贯击数也不断增加,花岗岩残积土的风化是由上至下的过程;利用平板载荷试验,场地内花岗岩残积土的极限荷载为740 kPa,由此可以反演出土体的强度和变形参数。 相似文献
4.
强降雨易诱发风化花岗岩边坡浅层滑坡,其滑坡滑动面多位于具有较大孔隙尺寸的强风化带。通过对广西玉林与梧州交界处风化花岗岩边坡浅层滑坡的现场勘查和对不同层位的土体进行物理力学试验,研究了饱和度对湿热地区风化花岗岩双层土质边坡抗剪强度的影响,发现两个风化带土体都存在一个“最优饱和度”使抗剪强度达到峰值,但饱和度对抗剪强度指标的影响规律不同,即饱和度对黏聚力影响很大,对内摩擦角影响很小;花岗岩全风化带与强风化带土体性质差异明显,尤其表现在饱和度影响下抗剪强度特性方面,从基质吸力理论和颗粒间胶结作用角度分析所发现的现象,可以清楚地解释产生差异的机制,为风化花岗岩边坡的开挖和滑坡的防治提供理论基础。 相似文献
5.
吕梁山脉东麓花岗岩风化土的工程类型与我国南方以及日本、韩国等地的花岗岩风化土有较大差别。为了对吕梁山压实花岗岩风化土的物理力学性状有较全面认识,通过常规土工试验、X射线衍射试验、大固结试验、大三轴试验等方法,对其击实特性、承载特性、变形特性、剪胀特性、强度特性等进行了分析。结果表明：黏土掺量对花岗岩风化土的击实特性和承载特性影响较大,存在两个不同的黏土掺量界限值（约8%和4%）,分别使得试样密实状态和承载能力处于最优;试样不存在膨胀潜势,无膨胀性,为低压缩性材料;压实花岗岩风化土颗粒破碎的特点导致试样二次加载→卸载压缩曲线存在两次明显塑性变形增大的现象;剪切时由于试样内部颗粒历经压密→错动→翻越→破碎的过程,导致不同围压下试样表现出不同的剪胀性;剪切过程中由于颗粒破碎的存在,使得试样表现出强度非线性特点。 相似文献
6.
对于使用水泥与上海黏性土进行混合加固的土体,其强度增长特性与水泥含量、加固土的初期pH值、养护时间有关。以上海4类黏土为研究对象,对加固土的强度增长特性进行了试验研究;探讨了加固土的养护时间、水泥含量、初期pH等与加固土强度的关系。试验结果表明,当上海黏土中水泥含量或者加固土的初期pH值大于某一临界值时,水泥加固土的强度将迅速增加,对于上海黏土,该临界pH值为11.7,对应的水泥含量为17%～20%。但当水泥含量达到一定值后,它对土体的pH值的影响开始变小,而且水泥土的强度趋于稳定的时间变长。 相似文献
7.
崩岗破坏是红层土中特有的破坏形式,在花岗岩风化土中发育更为强烈,这与花岗岩风化土自身的力学性质有关。本文认为花岗岩风化土自身的结构性、粒间吸力特性决定了其遇水软化和崩解的性质,花岗岩风化土软化主要表现为减压软化和损伤软化,花岗岩风化土颗粒粒径和孔隙大小不均匀性,以至土体在吸水过程中吸力不平衡导致其崩解作用。花岗岩风化土遇水发生软化和崩解是崩岗发生的内因,为崩岗破坏水土流失提供了物质来源,长期的水与重力作用是崩岗发生的外因,为崩岗持续发展提供了动力,在上述内因和外因作用下,最终形成了崩岗地貌。 相似文献
8.
《岩土力学》2017,(Z2):9-17
非饱和黏土中液相与固相基质间的相互作用,依据其形成机理的不同可分为毛细作用和物理-化学作用,目前建立的非饱和土强度模型多是基于毛细机理建立的,忽略了后者对土体强度的贡献。现有非饱和土强度理论仍建立在土体受压缩剪切作用的基础上,不适用于分析土的抗拉强度和拉剪耦合强度。为了能够全面地、合理地描述非饱和黏土的强度作用机制,建立了一个适用于非饱和黏土的二元介质压剪强度模型,将非饱和黏土抽象为理想毛细部分和理想吸附由两个理想部分组成,针对两者分别建立了理想强度公式,利用参与函数反映土中两种理想部分所占的比重,描述实际情况下土体的强度特征。在压剪强度模型的基础上,通过考虑非饱和黏土中的拉剪联合作用,建立了非饱和黏土的张拉-剪切耦合强度模型,给出了张拉-剪切耦合强度公式。利用强度模型对非饱和黏土的压剪强度及张拉-剪切耦合强度进行预测,预测结果和已有试验数据的对比结果表明所建模型能够较好地描述非饱和黏土的强度特征。 相似文献
9.
花岗岩风化土属于一种区域性特殊土,易扰动,其力学指标的确定多采用原位测试手段。通过对厦门地铁轨道交通1号线3个站点的典型花岗岩风化层开展地震扁铲侧胀试验,系统评价该类土的原位力学特性。结果表明,厦门花岗岩残积土土质分类为粉土-砂性土,具有似超固结特性,计算OCR值普遍大于1,排水特性属于部分排水类型;花岗岩残积土的力学性质指标对风化程度特别敏感,随埋深增加,风化程度逐渐减弱,土质分类由粉土向砂性土转化,土体水平应力减小,强度与刚度增加,剪切波速值逐渐增大,似超固结特性逐渐减弱,排水特性逐渐从非排水型向排水型过渡;利用剪切波速和土类指数ID可以较好地对花岗岩风化土进行土质分类。地震扁铲侧胀试验（SDMT）作为一种新型改进原位测试手段,试验结果能较好反映花岗岩风化层物理力学性能,具有一定的可靠性与较广泛的适用性。论文研究结果对厦门地区花岗岩风化土地基的优化设计具有直接的指导与借鉴意义。 相似文献
10.
旁压试验经过不断完善、发展、应用和推广,在与静力载荷试验、标准贯入试验等原位测试的比较中已凸显其优势,业已成为工程地质评价、地基承载力确定等实用可靠的方法。针对强风化花岗岩土体松散、土质较硬、取样和室内物理力学试验的困难,进行高压旁压器风化花岗岩原位测试,取得具有工程应用价值的成果,结果表明,虽然风化花岗岩由于受差异风化形成水平向不均匀性的影响,测试结果各指标间的相关性与黏土存在一定的差异,但黏土和风化花岗岩地基承载力随测点深度、变形模量与基床系数,地基承载力、变形模量和基床系数与标贯击数间均具有一定的线性相关关系,并对相关关系进行拟合,给出相应地拟合公式。 相似文献
11.
Effect of Cement and Quarry Dust on Shear Strength and Hydraulic Characteristics of Lithomargic Clay
The lithomargic clay constitutes an important group of residual soils existing under lateritic soils. This soil is found on
the western and eastern coasts of India over large areas. This soil is a problematic one and is very sensitive to water and
loses a greater part of its strength when becomes saturated. These high silt deposits have invited many problems such as slope
failures, foundation failures, embankment failures, uneven settlements etc. In this investigation an attempt is made to study
the effect of cement and quarry dust on shear strength and hydraulic characteristics of the lithomargic clay after the stabilization.
Microfabric and mineralogical studies were carried out to find out the reason for the strength development of the stabilized
soil using SEM and XRD analysis. The results indicated that there is an improvement in the properties of the lithomargic clay
with the addition of cement and quarry dust. The XRD results indicated the formation of CSH and CAH, which are responsible
for strength development in the stabilized soil. 相似文献
12.
全风化花岗岩孔径分布-颗粒组成-矿物成分变化特征及指标相关性分析 总被引：2，自引：0，他引：2
孔径分布、颗粒组成和矿物成分是全风化花岗岩微观和结构特征的3个主要方面,也是决定其工程地质性质的关键因素。理论研究和实际工程中,常用大、中小和微孔隙、角砾、砂粒和粉粘粒、三大矿物（石英、长石和粘土矿物）含量等指标表征这3方面的特征。3方面指标在一定范围上变化幅度多大？数值间相关性及作为土结构模型组份因子,它们相对权重多大？通过对香港九龙两处边坡51件全风化花岗岩试样压汞测试、颗粒分析和X射线衍射（XRD）等微观结构特征分析,结果表明：两处边坡粗粒和细粒结构全风化花岗岩有明显区别,前者主要属于砾石土和砂砾土,部分为含砾土,大孔隙多,石英和粘土矿物多,而后者部分属含砾土,部分为细砂土和亚砂土,微孔隙多,长石多;两者长石和粘土矿物含量变化正好相反。借助于多因素关系矩阵法,对3方面共9个指标作相关分析发现,相关性较好的指标是：角砾和砂粒 (0.948);大孔隙和微孔隙(0.846);石英和长石(0.827);长石和粘土矿物 (0.747)。从土结构因子角度考虑,权重从大到小指标是：微孔隙、长石、粘土矿物、砂粒、角砾、大孔隙、中小孔隙、粉粘粒和石英。其分析结果可为该类土微观结构特征细化及分类提供依据,为其微结构力学研究提供基础材料。 相似文献
13.
从近代海相地貌特征分析了江苏海相软土的形成。通过室内外试验数据的分析研究发现,该海相软土属于高含水率、高压缩性、高孔隙比、高液限、低承载力的淤泥质海相灵敏性软土。根据工程实践提出了有关海相软土加固处理的设计方法、施工技术的建议。 相似文献
14.
矿渣胶凝材料固化软土的力学性状及机制 总被引：4，自引：0，他引：4
利用矿渣胶凝材料固化软土,既可利用工业废渣,又能减少水泥的用量。以矿渣胶凝材料固化黏土、砂土二种软土。发现矿渣胶凝材料加固软土的效果远好于水泥、石灰,其9 %掺量的固化土28 d的无侧限强度达到2.0 MPa以上,普遍高于15 %掺量的水泥固化土,且其28 d固化土的软化系数普遍高于90 %以上,固化黏土后CBR值远高于同掺量的石灰固化土。X衍射结构分析表明,矿渣胶凝材料水化时产生的高强难溶的矿物晶体是其固化软土效果好的主要原因。因此,矿渣胶凝材料是一种性能优异的软土加固材料。 相似文献
15.
Neeraj Kumar Sharma S. K. Swain Umesh C. Sahoo 《Geotechnical and Geological Engineering》2012,30(5):1197-1205
Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity. 相似文献
16.
Peat has been considered as an organics remnant that suffers decomposition process throughout times under overburden pressure. Composition of peats normally consists of organics materials which sometimes exceed 75% specifically from woods that grows in marshes and places in conditions where deficiencies of oxygen exist. Usually peat area related with swampy and normally a low shear strength region. High compressibility is significant and often related to problematic soil for construction purposes. In this article, extensive number of studies are reviewed to understand the behavior of the peat after being stabilized. New findings indicated that the peat contents differs from one location to another, thus inevitably gives different behavior. Many improvisation methods have been put forward such as chemical stabilization, cement stabilization, deep mixing and fiber reinforcement to name a few to enhance the strength properties of the peat. This is mainly for construction reliability purposes. However, the suitability of the ground improvement for peat thus depend on its fundamental properties and cost involve for any dedicated ground construction work. This paper review the properties of peat in Malaysia and reviewed recent development in the peaty soil stabilization in Malaysia. It is also compared the materials used for the peat stabilization and the expansive clay soils as the main two problematic soils. 相似文献
17.
《Geomechanics and Geoengineering》2013,8(4):259-273
An important design parameter in cement-grouted soil nailed structures is the shear strength at the interface between the grouted nail and the surrounding soil. Both field and laboratory pull-out tests are normally used to investigate this interface shear strength. However, these tests have some limitations. In this study, direct shear box tests are adopted to investigate the interface shear strength behaviour between a completely decomposed granite (CDG) soil and a cement grout plate. Tests were carried out in a large direct shear test apparatus over a range of constant normal stress, soil moisture content, and soil–cement grout interface surface waviness. The laboratory test procedures are briefly described and the main test results are presented, followed by a discussion of the shear behaviour of the soil–cement grout interface. The interface shear behaviour is compared with the shear strength behaviour of the same soil tested under comparable conditions. It is shown that the shear stress–displacement behaviour of the soil–cement grout interface is similar to that of the soil alone. The test results indicate that the interface shear strength of the CDG and cement grout material depends on the normal stress level, the soil moisture content, and the interface surface waviness. 相似文献
18.
Clay soil with low-bearing capacities can present great problems underlying pavement and light structures due to uncertainty associated with their performance. This paper describes a sonic based testing methodology for quality control of a surface stabilized soil. From an engineering aspect, an increase in water content has a number of disadvantageous consequences: cohesion decreases, the soil swells, the alternating dry-out/shrinkage and wetting/swelling effects destroy the rock or a soil structure. Cement is mixed into the soil to increase both the strength and the usability of local soils in constructions purposes. This is to overcome the problems by strengthening the soil underlying the structure or diminishing the leads transmitted from the foundation to the soil. The compressive strength of the stabilized soil is highly dependent on the type of soil, moisture content, cement content, and compaction work, and can therefore vary significantly in the field. The authors performed the quality control by measuring the sonic and tensile strength velocity in the stabilized soil that has been correlated to compressive strength in native materials. The improvement of the soil materials by the addition of cement could make the material suitable as filling materials, foundation and/or a road base construction. The quality control for the stabilized soils was investigated using sonic measurements and strength gain. The test methods were performed to evaluate the degree of improvement achieved through the measurement of compression and shear-wave velocities of the soil under study. Scanning electron microscopy and electron dispersive X-ray analyses were performed on raw and laboratory treated for qualitative understanding the strength minerals formed during stabilization. The sonic test showed a considerable improvement with curing time and percentages of stabilizer. Mineralogical studies indicated the formation of silica and alumina hydrates along with interwoven structure of cement treated clay particles suggesting adequate mixing of the soil and binder owing to the strength of the soil materials. 相似文献
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浙江漩门三期围垦项目中采用爆炸挤淤置换法进行筑堤工程,为了对爆炸置换后海堤的固结沉降预测及稳定性评价提供可靠的试验参数,取爆炸前后地基范围内的海相软黏土,进行一维压缩和各向等压固结试验,并对该地区软土的压缩变形与结构特性进行初步研究。试验结果表明,海相软黏土存在一定的结构特性,表现出与其重塑土不同的性质;通过引入孔隙指数的概念,研究该地区软黏土的结构性,证实土体结构性的存在是其压缩特性不同于重塑样压缩曲线的内在原因,在高压力范围内其压缩曲线趋近于固有压缩曲线。爆炸挤淤作用对海相软黏土产生较强的扰动效应,也对其基本物理性质与压缩特性均产生重要影响;扰动效应造成软黏土的结构屈服应力降低,结构强度下降,采用新定义的结构破坏比来定量评估爆炸挤淤作用对海相软黏土结构性的破坏程度,可为爆炸挤淤置换法处理软基的海堤工程提供一定的理论基础。 相似文献