滨海氯盐盐渍土加固工程特性

盐渍土广泛分布于我国东部沿海地区,在工程建设中常出现溶陷、盐胀及腐蚀性等病害,对工程建设造成了极大地危害。试验采用成都理工大学自主研制新型抗盐胀固化材料SD作为固化剂对人工配置氯盐盐渍土进行室内试验,研究固化剂对氯盐盐渍土工程特性的影响。试验表明,抗盐胀固化剂可有效提高氯盐盐渍土强度,降低盐渍土膨胀性,固化剂掺量为2.5%,5%的试样28 d抗压强度相较于纯水泥试样分别增加56.72%,95.52%,抗折强度分别增加48.11%,52.53%;添加了固化剂试样线膨胀量约为纯水泥加固试样的的0.2倍。该固化剂有效提高了工程质量,延长其使用寿命,大大提高了工程经济效益。抗盐胀固化剂主要是通过抑制盐渍土中的盐离子与铝酸钙的反应即抑制Friedel盐和钙矾石的生成来达到固化氯盐盐渍土的目的。     

早期低温养护对固化超氯盐渍土强度的影响

采用自制固化剂对含盐量高达12.5%的超氯盐渍土进行固化,通过室内试验和现场试验研究早期低温养护对固化土强度的影响。结果表明:固化土在早期低温养护时强度增长缓慢,5℃时28d龄期仅为标准养护强度的44.7%,转入常温养护后,经过150d固化土强度最终能够达到标准养护条件下28d的固化土强度。根据对察尔汗盐湖地区冬季地温与试验条件的对比分析认为,固化土法在青海察尔汗盐湖地区冬季施工是可行的,但在施工中应注意由温度带来的强度与龄期关系的变化。     

滨海盐渍土作公路路基填料试验研究

滨海盐渍土是一种特殊土,具有溶陷、腐蚀等不良工程特性,如何将其作为资源用于公路路基填料已成为滨海地区交通建设发展中的重要岩土工程问题之一。从滨海盐渍土的工程应用角度出发,利用石灰、水泥和新型高分子固化材料SH对其进行固化试验研究,并分析探讨了龄期、制样用水、浸泡用水和土中含盐量对固化盐渍土强度的影响及其水稳性。试验结果表明:滨海盐渍土经石灰、水泥和SH综合固化处理后,其强度和水稳性能达到规范要求,可以用作公路路基填料。     

GGBS固化土在不同龄期下的无侧限抗压强度研究

湖积软土在合肥滨湖新区较为常见,进行工程建设时需要充分考虑湖积软土影响,对其采取科学化的固化处理。以GGBS(Ground Granulated Blastfurnace Slag,粒化高炉矿渣)作为固化剂固化合肥湖积软土,通过对合肥滨湖地区软土进行物理力学试验,并将不同掺入比(8%GGBS,14%GGBS)的GGBS固化土养护不同龄期(3d,7d,28d)后测其无侧限抗压强度,分析GGBS固化土在不同养护龄期下其无侧限抗压强度的变化规律。结果表明GGBS的加入使得固化土的抗压强度有了显著的提高,并且在一定范围内随着GGBS掺入比的提高、养护时间的增加,其抗压强度也会大大提高。     

滨海盐渍土固化后的工程特性试验研究

从滨海盐渍土的工程应用角度出发,利用石灰、水泥等固化材料对其进行固化试验研究,分析探讨了固化盐渍土抗压强度随固化剂含量、龄期、土中含盐量、饱水时间和干湿循环次数的变化规律。试验结果表明:滨海盐渍土经石灰、水泥固化处理后,其抗压强度和水稳性能得到较大程度的提高,可以达到规范要求,能用作公路路基填料。     

固化土强度和弹性模量特性研究

通过不固结不排水三轴剪切试验,研究固化剂掺量、围压2个因素对固化土强度和弹性模量的影响。研究表明:固化剂可有效提升路基填料的强度;随着固化剂掺量的增加,固化土的强度增加,应力-应变关系曲线软化程度更强。同时,固化剂掺量增加,影响土体弹性模量,呈增加趋势,且固化剂掺量越大影响越大。随着围压的增加,固化土的弹性模量也呈增加趋势,且围压越大影响越大。在土体加固技术方面固化剂具有广泛的应用前景。     

铁尾矿基地聚物固化盐渍软土的试验研究

为探究铁尾矿等固体废弃物规模化、高值化应用于沿海地区盐渍软土道路基层硬化的可能性,基于铁尾矿、粉煤灰、高炉矿渣和石粉等固废多动力源耦合重构,制备盐渍软土低碳环保固化剂。研究不同固化剂掺量对固化土无侧限抗压强度、冻融循环的影响。并采用X射线衍射、扫描电镜对20%固化剂掺量和原状土的微观结构进行分析,揭示了固化剂对盐渍土力学性质的影响机理。结果表明：固化剂掺量为10%时,7 d无侧限抗压强度达到0.88 MPa,满足一级公路路基设计标准;固化剂掺量为20%时,7、28 d抗压强度分别达到2.44、2.99 MPa,实现强度与经济性最优化。通过SEM分析技术,发现固化土中C-S-H和AFt充填土体颗粒之间,从而有效改善盐渍土的稳定性和强度。     

吹填海砂力学性质研究

随着沿海城市建设需要,围海造陆已经成为沿海工程建设和海岸开发中的重要组成部分,临海省高等级公路应用吹填海砂作为路基填料,为了研究海砂土的强度特性,对其已经固化土进行了无侧限抗压强度,试验结果表明：随着水泥和石灰含量增加,固化盐渍土的强度和水稳系数均增加,水泥的固化效果比石灰好;水泥固化海砂土表现为脆性破坏,出现明显的剪切破坏面,而石灰固化海砂土一般为塑性破坏,没有明显的剪切破坏面.     

硫酸盐渍土水泥加固盐胀抑制剂研究

硫酸盐渍土具有遇水溶陷、强度降低、盐胀-冻胀的特性,而传统加固材料如水泥、石灰等,由于SO_4~(2-)与水泥反应生成Aft·32H_2O,造成加固体膨胀、强度损失及耐久性降低。针对上述问题,利用自主研发的抗盐胀固化剂与水泥复配对盐渍土进行改良,探讨含盐量和固化剂对固化土膨胀性与力学性能的影响。试验结果表明,固化剂SD抑制膨胀、维持强度的能力优于纯水泥,在2%含盐量时,膨胀率降低65.2%~83.4%,抗压和抗折强度分别提高2~6倍;含盐量为5%时,膨胀率降低88.5%以上,抗压和抗折强度提高1.6~4.7倍。试验表明,在中盐渍土加固中,低掺量抑制膨胀性强;强盐渍土中,高掺量抑制膨胀率强。通过盐溶液稳定性试验和冻融试验对膨胀性进行了探讨,固化剂能够有效提高加固土的抗膨胀性,降低强度的损失率;在抗冻稳定性上,对冻胀有一定抑制作用,而对强度的稳定作用一般,表现为温度相应"迟滞"。     

微生物—活性氧化镁固化盐渍土强度变化规律研究

利用微生物—活性氧化镁固化技术改良滨海细粒氯盐盐渍土,通过不同氧化镁掺量条件下固化盐渍土的无侧限抗压强度试验、直剪试验及水稳性试验,探究此方法固化盐渍土的强度变化规律及改良效果,试验结果表明：微生物作用可明显促进活性氧化镁反应,加速固化盐渍土;活性氧化镁掺量增加,固化盐渍土的无侧限抗压强度和抗剪强度均随之增大,20%氧化镁掺量的固化盐渍土的抗压强度和抗剪强度(法向应力为100kPa时)分别是未改良盐渍土的8.18倍和8.21倍;黏聚力随着活性氧化镁掺量的增加明显增大,而内摩擦角呈现先增大后减小的趋势;活性氧化镁掺量增加,固化后盐渍土的水稳系数也增大,可明显改善盐渍土的水稳性。     

碱激发矿粉固化连云港软土试验研究

 为了减轻使用波特兰水泥作为软土固化剂存在的高能耗、CO2排放和不可再生资源消耗等环境问题,通过室内配合比试验初步研究碱激发矿粉对连云港软土的固化效果,并与水泥固化进行对比。结果表明：Na2CO3对矿粉固化土的激发效果非常有限;NaOH激发矿粉的效果最好,7 d,28 d,90 d无侧限抗压强度最高,但是在90 d后会发生一定的强度衰减;矿粉+电石渣固化土的7 d,28 d强度比水泥固化土低,而90 d,180 d强度比水泥固化土高。Na2CO3,NaOH和Na2SO4能够加速矿粉+电石渣固化土的强度增长速率,其中,Na2CO3的效果最弱,虽然可以在90 d内提高矿粉+电石渣固化土的强度,但180 d强度反而略低;NaOH激发的矿粉+电石渣固化土强度在7 d,28 d,90 d龄期均有较大的提高,但从90 d到180 d会发生强度衰减;Na2SO4激发矿粉+电石渣的效果最好,可以在实际工程中进行应用,不仅可以减小水泥生产过程带来的环境影响,还能提高软土固化效果,降低工程造价。     

Study on the optimization and performance of GFC soil stabilizer based on response surface methodology in soft soil stabilization

In order to improve the utilization efficiency of industrial waste residue and the treatment effect of marine soft soil, ground granulated blast furnace slag (GGBS), flue gas desulfurization gypsum (FGDG) and calcium carbide slag (CCS) were used to modify the waste soft soil in coastal areas. Using the box-behnken design (BBD) in response surface analysis, the optimal mix ratio design of GGBS, FGDG and CCS was obtained. Meanwhile, under the same conditions, the mechanical properties, durability and micro mechanism of industrial waste residue stabilized soil was studied and compared with that of OPC stabilized soil by the unconfined compressive strength (UCS) test, water stability test, freeze–thaw cycle test, X-ray diffraction and scanning electron microscope (SEM) test. Experimental results showed that the optimal mixing ratio of GGBS, FGDG and CCS was 61: 8: 31; the UCS of GFC stabilized soil exceeded 8.7 MPa at 28d. The UCS of GFC stabilized soil at 28d was 1.23 times higher than that of OPC stabilized soil. GFC stabilized soil also possessed superior durability than OPC stabilized soil. Micro mechanism analysis showed that gel hydration products (CSH, CAOH) and expansive hydration product (AFt) were produced in GFC stabilized soil. These hydration products led to the aggregation and condensation of soil particles, which made the soil structure denser through bonding and filling effects, thus increased strength of stabilized soil.     

碱激发高炉矿渣固化铅污染土酸缓能力、强度及微观特性研究

采用碱激发高炉矿渣对铅污染土进行固化稳定处理,并研究其固化稳定机理。结果表明:随着固化剂掺量提高,GGBS-MgO固化铅污染土酸缓能力的固化污染土酸缓冲系数β随之提高;铅能够抑制GGBS-MgO进行水化反应,致使GGBS-MgO固化铅污染土比表面积远低于同掺量的固化未污染土;GGBS-MgO固化铅污染土q_u均低于相同掺量下固化未污染土,且无侧限抗压强度与其比表面积间存在明显的线性关系;SEM和XRD结果显示,GGBS-MgO固化铅污染土和固化未污染土的试样,主要水化产物都为C-S-H与Ht;累积进汞量和孔径直径结果显示,GGBS-MgO固化未污染土累积进汞量高于固化铅污染土。     

Mechanical properties of stabilized artificial organic soil

In order to study the influence of organic matter on the mechanical properties of stabilized soil and the effect of XGL2005 on stabilizing organic soil, unconfined compressive strength tests were carried out. Test results indicated that the strength of stabilized soil decreased in the form of a logarithmic function as the organic matter content increased. In contrast, the strength increased in the form of a power function as the content of the stabilization agent increased. The strength of cement stabilized organic soil was reinforced greatly by adding the stabilizer XGL2005. Based on the law obtained from the test, a strength prediction model was established by regression analysis. The model included the influence of the curing time, the content of the cement, the organic matter content and the stabilization agent on the strength of stabilized soil.     

黄河三角洲改性含盐水泥土搅拌桩耐久性研究

通过室内试验,研究了黄河三角洲含盐水泥土的劣化规律以及粉煤灰和矿渣微粉对其劣化的抑制效应,并利用X射线衍射（XRD）和扫描电镜（SEM）对劣化机理及外加剂的改性机理进行了分析.结果表明：地下盐水环境对黄河三角洲水泥土有较强的腐蚀作用,其90,180d龄期的抗压强度分别降低了18.5%,21.6%;掺加粉煤灰对黄河三角洲含盐水泥土的早期强度不利,但其后期强度会持续增加;掺加矿渣微粉对黄河三角洲含盐水泥土强度有明显的提升作用,并对其劣化有显著的抑制作用.为防止黄河三角洲含盐水泥土劣化,工程中建议用粉煤灰和矿渣微粉等质量替代60%的水泥,而且矿渣微粉掺量不少于40%.     

专用水泥AGS及其稳定基层材料的性能研究

AGS专用水泥是由粒化高炉矿渣、石膏、水泥熟料及激活剂配制的一种新型细粒土结合料。该文研究AGS水泥对不同粒料的稳定作用,不同AGS掺量稳定粒料的稳定效果,延迟成型时间对AGS稳定粒料强度的影响,以及AGS稳定粒料劈裂抗拉强度和回弹模量,探讨AGS稳定粒料的线性收缩,并与水泥的相关性能进行了对比。结果表明AGS稳定土强度高,具有良好的抗裂性和较长的延迟成型时间,AGS稳定粒料是一类性能优良的路面基层材料。     

Mechanical properties and stabilizing mechanism of stabilized saline soils with four stabilizers

Saline soil used in embankment construction causes dissolution falling and salt swelling, which results in embankment cracking. Therefore, saline soils should be stabilized in engineering. The unconfined compressive strength test, triaxial compressive test, splitting tensile test, and fatigue test were conducted on six types of stabilized soils. Subsequently, scanning electron microscopy test, X-ray diffraction test, Fourier transform infrared spectroscopy test, and thermogravimetric analysis were performed to discover the stabilizing mechanism. Test results indicated that the mechanical properties of saline soil were improved by adding lime, cement, fly ash, and SH agent (SH). In particular, after soaking, the strength of the stabilized soil with SH was significantly enhanced, the deviatoric stress-strain curves transformed from strain softening to strain hardening, and the tensile property and fatigue resistance were improved as well. The SH generated a film and silk-like web, wrapped the soil particles, and filled the soil pores, which improved the strength and anti-deformation abilities of the stabilized soils.

     

Clayey soil stabilization using alkali-activated volcanic ash and slag

Lime and Portland cement are the most widely used binders in soil stabilization projects. However, due to the high carbon emission in cement production, research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years. This research investigated the potential of using alkali-activated ground granulated blast furnace slag (GGBS) and volcanic ash (VA) as green binders in clayey soil stabilization projects, which has not been studied before. The effects of different combinations of VA with GGBS, various liquid/solid ratios, different curing conditions, and different curing periods (i.e. 7 d, 28 d and 90 d) were investigated. Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests. The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels. Moreover, although VA needs heat curing to become activated and develop strength, its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles. The carbon embodied of the mixtures was also evaluated, and the results confirmed the low carbon footprints of the alkali-activated mixtures. Finally, it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.     

高含水量粘土固化剂的研究

采用水泥、单一外加剂和复合外加剂对高含水粘土进行固化试验，并运用Ｘ射线衍射和扫描电子显微照相等对加固土进行了分析。研究结果表明，当土壤含水量较高（４８％左右）时，在水泥中掺１４％的石膏及３％的硫酸钠，能大幅度提高固化土的强度；在硫酸盐外加剂的作用下，粘土中的活性氧化铝与Ｃａ（ＯＨ）２反应生成针状的钙矾石晶体，从而使土团与水化产物相互联接，大大提高稳定土的强度和水稳性；较多的钙矾石晶体的形成是硫酸盐外加剂能大幅度提高固化土强度的主要原因。     

矿渣混凝土的长期强度和抗冻融耐久性研究

通过试验研究,探讨了不同强度等级的矿渣混凝土和普通混凝土在７ ｄ,２８ ｄ,９０ ｄ,１８０ｄ,３６５ ｄ 龄期的抗压强度,研究了矿渣混凝土的抗冻融耐久性．试验表明,强度等级、养护条件、矿渣掺量等因素对矿渣混凝土的强度、抗冻融耐久性有着显著的影响;矿渣混凝土的抗冻融耐久性明显优于同等级的普通混凝土;矿渣掺量愈大,矿渣混凝土的抗冻融耐久性愈差