Utilization of sodium waterglass from sugar cane bagasse ash as a new alternative hardener for producing metakaolin-based geopolymer cement     

《Chemie der Erde / Geochemistry》2017,77(2):257-266

Sugar cane bagasse ash from SOSUCAM company in Cameroon was used to synthesize sodium waterglass as a new alternative hardener. The new hardener was used to prepare metakaolin-based geopolymer cements. The compressive strength of the resulting geopolymer cement cured at room temperature for 28 days was 32.9 MPa. Samples soaked for 28 days in water in parallel experiments revealed a strength of 31.4 MPa. This shows that exposure of water does not lead to any weakening. The value of water absorption was 7.1% in the water-soaked cements, indicating the presence of fewer pores and voids than in the dry cements. However, in SEM micrographs, the microstructure of geopolymer cement appears rather homogeneous and compact without any change by water soaking. It can thus be concluded that sodium waterglass from sugar cane bagasse ash can be used as an alternative hardener or reactive ingredient for producing geopolymer cement with a high degree of cross-linking geopolymer framework. The use of this low-value silica-rich waste for producing sodium waterglass results in environmental benefits including a significant reduction of CO₂ emission and energy consumption compared to the production of commercial sodium waterglass.  相似文献   

Calibration of resistance factor for design of pile foundations considering feasibility robustness     

《Computers and Geotechnics》2017

The resistance factor for pile foundations in load and resistance factor design (LRFD) is traditionally calibrated considering target reliability index (β_T) and statistics of load and resistance bias factors. However, the resistance bias factor is hard to quantify statistically. Consequently, the design obtained using the calibrated resistance factor can still miss β_T if the variation in resistance bias factor has been underestimated. In this paper, we propose a new resistance factor calibration approach to address this dilemma by considering “feasibility robustness” of design in the calibration process. Herein, the feasibility robustness is defined as a probability that the β_T requirement can still be satisfied even in the presence of uncertainty or variation in the computed bearing capacity. For illustration, LRFD approach for pile foundations commonly used in Shanghai, China is examined. Emphasis is placed on re-calibration of resistance factors at various feasibility robustness levels, with due consideration of the variation in the resistance bias factor. A case study is presented to illustrate the use of the re-calibrated resistance factors. The results show that the feasibility robustness is gained at the expense of cost efficiency; in other words, the two objectives are conflicting. To aid in the design decision-making, an optimal feasibility robustness level and corresponding resistance factors are suggested in the absence of a designer’s preference.  相似文献   

Numerical investigation on the impact resistance of road barriers of Micropile-MSE Wall for subgrade     

《Computers and Geotechnics》2017

The Micropile-MSE Wall, specially designed for mountain roadways, is used to simultaneously increase the MSE wall’s local stability, global stability and impact resistance of road barriers. Model tests were conducted first to validate the viability of the Micropile-MSE Wall. The impact resistance of the road barrier is then studied numerically. The test results indicate that the surcharge-induced earth pressure, base pressure and lateral displacement of Micropile-MSE Wall panels are effectively reduced. The impact loading on the barriers of the Micropile-MSE Wall is actually supported by the whole retaining structure, which increases the impact resistance of the road barrier significantly.  相似文献   

On behavior of load transfer for drilled shafts embedded in weak rocks     

《Computers and Geotechnics》2017

This study deals with the formulation of an analytical solution for load transfer in drilled shaft and its application. The emphasis is on quantifying the mobilization of side resistances, which are closely related to shear behaviors of the concrete-rock interface. In this modelling, the side resistance is idealized by using elasticity-brittleness-plasticity, and a simple slip-line field is built to identify the critical shear displacement. The closed-form solution of load transfer is obtained by using the proposed shear model. Comparison between predictions and field observations is also made to validate performance of the proposed method.  相似文献   

Cone penetration test in sand: A numerical-analytical approach     

《Computers and Geotechnics》2017

Separation of the effects of initial horizontal stress and relative density on cone tip resistance in sandy soils has been a complicated issue for many years. In order to overcome this problem, a numerical modeling of CPT which has been verified by calibration chamber tests, has been used in this paper to achieve a reliable analytical solution. The analytical solution has resulted in two relationships for sleeve friction and cone tip resistance in terms of the initial conditions of sandy soil. Based on the presented solution, the initial horizontal stress and relative density can be determined according to CPT measurements.  相似文献   

双排抗滑桩上滑坡推力近似解析方法     

肖世国  何洪 《岩土力学》2015,36(2):376-380

双排抗滑桩是加固大型滑坡的常用工程措施之一,在实际工程设计计算中的关键环节在于简单且合理地确定作用于前后排桩上的滑坡推力。将抗滑桩受荷段前侧坡体视为水平向的温克勒（Winkler）地基,基于弹性地基梁模型,并充分考虑桩体受荷段与锚固段的变形连续性,通过迭代算法确定出后排抗滑桩受荷段前侧坡体抗力,进而可对排间坡体采用传递系数法计算出前排桩桩后滑坡推力,给出了相关的理论计算公式。通过室内模型试验验证了所提方法的合理性,并针对一大型基覆式滑坡实例,具体计算出了前后排桩上的设计滑坡推力荷载。所提计算方法可为实际工程的简化设计提供参考。  相似文献   

不同平衡堆载条件下桩基承载特性的原位试验研究   总被引：1，自引：0，他引：1  

邓会元  戴国亮  龚维明  朱中发 《岩土力学》2015,36(11):3063-3070

沿海吹填围垦地区土质较差,淤泥软弱土层较厚,在后期填土作用下土体会产生很大的固结沉降。后期不同堆载填土方式对桥梁基础影响较大,可降低基桩承载力,同时平衡堆载主要增加基桩的沉降,而不平衡堆载则对基桩水平位移影响较大。结合台州湾大桥工程建设,选取3根基桩进行了平衡堆载（围载）试验,另外,选取了3根基桩进行了不平衡堆载试验,研究不同堆载条件下对桩基承载特性的影响。现场试验结果表明,平衡堆载条件下主要引起桩侧产生负摩阻力,堆载高度达到4 m,堆载面积为24 m×16 m时,负摩阻力总和达到2 687 kN左右,中性点深度约为29.5 m,约为0.36倍桩长,且负摩阻力的发展是随时间而变化的;不平衡堆载条件下主要产生土拱效应,使桩基产生较大的水平位移,试验中不平衡堆载对吹填区的影响主要在距离地面20 m范围之内,土中最大水平位移出现在距离地面4～5 m左右位置,而桩身最大水平位移出现在桩顶。  相似文献   

Test method and experimental research on resistance of oil shale under high temperature   总被引：1，自引：0，他引：1  

《世界地质(英文版)》2012,(3):245-251

Heating the oil shale by current underground to accomplish in-situ transformation process, is a viable direction. The electrical properties of oil shale under different temperatures, especially the resistance, become important. Charging oil shale underground to heat oil shale till kerogen’s decomposition temperature, then crude oil and other gases can be generated. The resistance of the oil shale samples was measured by Direct Current (DC) quadripole method to find out the variation rules of resistance value. In the experiments, oil shale presented its semiconductor property. When heated till 350℃-450℃, its resistance changed greatly, optional for heating and cracking. The porosity, oil content, media and composition affected the resistance largely.  相似文献   

基坑工程平面竖向弹性地基梁法中土的水平抗力比例系数反分析研究     

徐中华  李靖  王卫东 《岩土力学》2014,35(Z2):398-404

提出了一种结合Ucode反分析软件和Abaqus有限元分析软件,并根据围护墙实测变形来反分析基坑工程平面竖向弹性地基梁法中土的水平抗力比例系数的方法。重点讨论了反分析的原理和实现流程,给出了反分析过程中迭代控制参数的确定方法及待估参数取值的确定方法。通过参数敏感分析可找到对围护结构变形影响较大的土层,针对起主导作用的土层m值进行反分析,既可提高迭代效率,又能保证反分析结果的准确性。实际工程反分析的结果表明,计算值与实测围护墙变形吻合得很好。在此基础上,根据多个测孔的反分析结果给出了各层土的水平抗力比例系数的建议取值。  相似文献   

让压锚索在边坡支护中的应用试验研究及摩阻力问题的探讨     

汪波  徐建强  吴正恺  朱安龙  王勇 《岩土力学》2014,35(12):3370-3376

为研究让压锚索在边坡支护中的自身让压特性,获取让压实测资料,以江西洪屏电站高边坡为工程背景,结合图强工程材料有限公司研发的新型让压锚索,针对不同锚索长度、自由段长度等各种工况进行了现场试验,试验表明：在让压锚索张拉过程中,部分锚索出现了让压滑移现象,让压效果显著;但让压时,长锚索孔口张拉力与设计基础让压力相差很大,说明锚索孔口张拉力并未如理想状态那样全部传递给锚孔内部的锚索,而是很大一部分孔口拉力将用来克服锚索与锚孔之间的摩阻力,且量值上已达到不容忽视的程度。试验同时揭示了锚索长度、锚固长度、锚束及锚孔施工质量对摩阻力的大小起到关键性影响,锚索长度、自由段长度越长、锚束越多、锚孔质量越差,则摩阻力越大。并据此提出了未来边坡防护锚索设计中重点关注及有待于进一步研究的内容。  相似文献