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Performance of cement-stabilized sand subjected to freeze-thaw cycles 冻融循环作用下水泥稳定砂的性能
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.1.041
Assel Jumassultan, Nazerke Sagidullina, Jong R. Kim, T. Ku, Sung-Woo Moon
In cold regions, the integrity of the infrastructures built on weak soils can be extensively damaged by weathering actions due to the cyclic freezing and thawing. This damage can be mitigated by exploiting soil stabilization techniques. Generally, ordinary Portland cement (OPC) is the most commonly used binding material for investigating the chemo-hydro-mechanical behavior. However, due to the environmental issue of OPC producing a significant amount of carbon dioxide emission, calcium sulfoaluminate (CSA) cement can be used as one of the eco-sustainable alternatives. Although recently several studies have examined the strength development of CSA treated sand, no research has been concerned about CSA cement-stabilized sand affected by cyclic freeze and thaw. This study aims to conduct a comprehensive laboratory work to assess the effect of the cyclic freeze-thaw action on strength and durability of CSA cement-treated sand. For this purpose, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests were performed on the stabilized soil specimens cured for 7 and 14 days which are subjected to 0, 1, 3, 5, and 7 freeze-thaw cycles. The test results show that the strength and durability index of the samples decrease with the increase of the freeze-thaw cycles. The loss of the strength and durability considerably decreases for all soil samples subjected to the freeze-thaw cycles. Overall, the use of CSA as a stabilizer for sandy soils would be an eco-friendly option to achieve sufficient strength and durability against the freeze-thaw action in cold regions.
在寒冷地区,由于循环冻融作用,软弱土壤基础设施的完整性会受到严重破坏。利用土壤稳定技术可以减轻这种损害。一般来说,普通硅酸盐水泥(OPC)是研究化学-流体-力学行为最常用的粘结材料。然而,由于OPC产生大量二氧化碳排放的环境问题,硫铝酸钙(CSA)水泥可以作为生态可持续的替代品之一。虽然最近有一些研究对CSA处理砂的强度发展进行了研究,但尚未有研究关注循环冻融对CSA水泥稳定砂的影响。本研究旨在开展综合的实验室工作,评估循环冻融作用对CSA水泥处理砂强度和耐久性的影响。为此,对固化7天和14天的稳定土试件进行了0、1、3、5和7次冻融循环的无侧限抗压强度(UCS)和超声脉冲速度(UPV)试验。试验结果表明,随着冻融循环次数的增加,试件的强度和耐久性指标逐渐降低。冻融循环对所有土壤样品的强度和耐久性损失均有显著降低。总的来说,使用CSA作为沙质土壤的稳定剂将是一种环保的选择,可以在寒冷地区实现足够的强度和耐久性,以对抗冻融作用。
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引用次数: 11
Measurements and analysis of load sharing between piles and raft in a pile foundation in clay 粘土桩基础中桩与筏板荷载分担的测量与分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.6.559
K. Watcharasawe, P. Jongpradist, P. Kitiyodom, Tatsunori Matsumoto
This research presents the monitoring results and their interpretation on load sharing of the pile foundation during the construction of a high-rise (124 m in height) building in Bangkok, in soft clayey ground. Axial forces in several piles, pore water pressure and earth pressures beneath the raft in a tributary area were monitored through the construction period of the building. The raft of the pile foundation in soft clayey ground can share the load up to 10-20% even though the foundation was designed using the conventional approach in which the raft resistance is ignored. The benefit from the return of ground water table as the uplift pressure is recognized. A series of parametric study by 3D-FEA were carried out. The potential of utilizing the piled raft system for the high-rise building with underground basement in soft clayey ground was preliminarily confirmed.
本文介绍了曼谷某高层建筑(高124米)在软粘土地基上施工过程中桩基荷载分担的监测结果及其解释。在整个建筑施工期间,监测了几根桩的轴力、支流区域筏板下的孔隙水压力和土压力。在软粘土地基中,即使采用忽略筏板阻力的传统设计方法,桩基筏板也能分担10-20%的荷载。认识到地下水位作为上扬压力的回归所带来的效益。采用三维有限元法进行了一系列参数分析。初步确定了桩筏体系在软粘土地基中具有地下地下室的高层建筑中的应用潜力。
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引用次数: 2
Quantitative assessment on the reinforcing behavior of the CFRP-PCM method on tunnel linings CFRP-PCM法对隧道衬砌加固性能的定量评价
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.2.123
Wei Han, Yujing Jiang, Xuepeng Zhang, D. Koga, Yuan Gao
In this paper, the carbon fiber reinforced plastic (CFRP) grids embedded in polymer cement mortar (PCM) shotcrete (CFRP-PCM method) was conducted to repair the degraded tunnel linings with a cavity. Subsequently, the reinforcing effect of the CFRP-PCM method under different degrees of lining deterioration was quantitatively evaluated. Finally, the limit state design method of the M-N interaction curve was conducted to determine whether the structure reinforced by the CFRP-PCM method is in a safe state. The main results indicated that when the cavity is at the shoulder, the lining damage rate is more serious. In addition, the remarkably reinforcing effect on the degraded tunnel linings could be achieved by applying a higher grade of CFRP grids, whereas the optimization effect is no longer obvious when the grade of CFRP grids is too high (CR8); Furthermore, it is found that the M-N numerical values of the ten reinforcing designs of the CFRP-PCM method are distributed outside the corresponding M-N theoretical interaction curves, and these designs should be avoided in the corresponding reinforcing engineering.
本文采用碳纤维增强塑料(CFRP)网格嵌入聚合物水泥砂浆(PCM)喷射混凝土(CFRP-PCM法)修复退化的含空腔隧道衬砌。随后,定量评价了CFRP-PCM方法在不同衬砌劣化程度下的补强效果。最后,采用M-N相互作用曲线的极限状态设计方法,确定经CFRP-PCM方法加固的结构是否处于安全状态。主要结果表明,当空腔位于肩部时,衬里损伤率更严重。此外,采用较高等级的碳纤维布格栅对退化的隧道衬砌具有显著的加固效果,而当碳纤维布格栅等级过高时,优化效果不再明显(CR8);此外,还发现CFRP-PCM方法的10种加固设计的M-N数值分布在相应的M-N理论相互作用曲线之外,在相应的加固工程中应避免这些设计。
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引用次数: 3
Stability analysis of coal face based on coal face-support-roof system in steeply inclined coal seam 基于工作面-支护-顶板系统的急倾斜煤层工作面稳定性分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.3.233
D. Kong, Y. Xiong, Zhanbo Cheng, Nan Wang, Guiyi Wu, Yong Liu
Rib spalling is a major issue affecting the safety of steeply inclined coal seam. And the failure coal face and support system can be affected with each other to generate a vicious cycle along with inducing large-scale collapse of surrounding rock in steeply inclined coal seam. In order to analyze failure mechanism and propose the corresponding prominent control measures of steeply inclined coal working face, mechanical model based on coal face-support-roof system and mechanical model of coal face failure was established to reveal the disaster mechanism of rib spalling and the sensitive analysis of related factors was performed. Furthermore, taking 3402 working face of Chen-man-zhuang coal mine as engineering background, numerical model by using FLAC3D was built to illustrate the propagation of displacement and stress fields in steeply inclined coal seam and verify the theory analysis as mentioned in this study. The results show that the coal face slide body in steeply inclined working face can be observed as the failure height of upper layer smaller than that of lower layer exhibiting with an irregular quadrilateral pyramid shape. Moreover, the cracks were originated from the upper layer of sliding body and gradually developed to the lower layer causing the final rib spalling. The influence factors on the stability of coal face can be ranked as overlying strata pressure (P) > mechanical parameters of coal body (e.g., cohesion (c), internal fraction angle (𝛟)) > support strength (F) > the support force of protecting piece (F
肋剥落是影响大倾斜煤层安全生产的主要问题。急倾斜煤层破坏工作面与支护系统相互影响,形成恶性循环,诱发大面积围岩坍塌。为了分析急倾斜工作面破坏机理,提出相应的突出控制措施,建立了基于工作面-支护-顶板系统的力学模型和工作面破坏力学模型,揭示了肋层剥落的灾害机理,并对相关因素进行了敏感性分析。并以陈满庄煤矿3402工作面为工程背景,利用FLAC3D软件建立数值模型,对急倾斜煤层中位移场和应力场的传播规律进行了模拟,验证了本文的理论分析。结果表明:急倾斜工作面滑体表现为上层破坏高度小于下层破坏高度,呈不规则四边形棱锥状;而且,裂纹从滑体的上层开始,逐渐向下层发展,最终导致肋层剥落。影响工作面稳定性的因素依次为:上覆岩层压力(P)、煤体力学参数(如:黏聚力(c)、内分数角()、支护强度(F)、护块支护力(F)
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引用次数: 33
Effects of fly ash column treatment of HP clayey soils on seismic behavior of R/C structures 粉煤灰柱处理HP粘土对R/C结构抗震性能的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.6.473
Baran Toprak, S. Bas, I. Kalkan
The behavior of soil directly affects not only its stability condition but also structural response of structural systems. High-plasticity clay soil (CH) is vulnerable to volumetric swelling leading to different settlements in structural systems. Hence, it becomes indispensable to propose practical solutions to reducing this effect. In the present study, structural response of R/C frame buildings, resting on high plasticity clayey soils strengthened through the coal fly ash column technique, to earthquake motion is investigated. For this aim, the swelling behavior of high plasticity clay soil (CH) is identified with in-situ experimental tests on the regions with high swelling potential in the city of Kirikkale, Turkey. In order to reduce the swelling potential of the investigated regions, the coal fly ash column technique was implemented to the reference soil specimen with high swelling percentage of 15.6%. Experimental results obtained from the strengthened soil specimens were compared to those from the reference specimen. This comparison revealed that the coal fly ash column approach has a considerable effect on improving the swelling behavior of the high plasticity clay soil. The decrease in the volumetric swelling value is also thought to directly improve the response of a building structure settled on high plasticity clay soil. The improvement in the seismic response of existing R/C structures located in the regions with high swelling potential was identified by adopting the increased allowable bearing pressure value of the improved soil in the analyses. Based on the comparative study, structural earthquake response of R/C frame systems was investigated on the basis of the engineering parameters, including the base-shear force, base overturning moment, base axial force and settlement of foundation. The percent changes in these values showed that the base axial force and settlement of foundation were improved with the help of this strengthening application.
土的特性不仅直接影响到土的稳定状态,而且直接影响到结构体系的结构响应。高塑性粘土易受体积膨胀的影响,从而导致结构体系的不同沉降。因此,有必要提出切实可行的解决方案来减少这种影响。本文研究了采用粉煤灰柱加固高塑性粘土地基的R/C框架结构在地震作用下的结构响应。为此,通过对土耳其基里卡莱市高膨胀潜力区域的现场试验,对高塑性粘土(CH)的膨胀行为进行了识别。为了降低研究区域的膨胀势,对膨胀率高达15.6%的参考土样采用了粉煤灰柱技术。将加固土试件的试验结果与参考试件进行了比较。结果表明,粉煤灰柱法对改善高塑性粘土的膨胀特性有相当大的作用。体积膨胀值的降低也被认为直接改善了建筑结构在高塑性粘土上的响应。在分析中采用改良土提高许用承载压力值,发现位于高膨胀潜力区域的既有R/C结构的地震反应得到改善。在对比研究的基础上,以基础剪力、基础倾覆力矩、基础轴力、基础沉降等工程参数为基础,研究了R/C框架体系的结构地震反应。这些数值的百分比变化表明,该加固措施改善了地基的基底轴力和沉降。
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引用次数: 1
Risk assessment of water inrush in karst shallow tunnel with stable surface water supply: Case study 地表供水稳定的岩溶浅埋隧道突水风险评价——以实例为例
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.6.495
Zengguang Xu, Meiting Xian, Xiaofeng Li, Wei Zhou, Jiaming Wang, Yaping Wang, J. Chai
Water inrush generally has a serious impact on karst shallow tunnel construction. Because of in situ fault fracture zone, high degree of weathering and poor quality of rock mass,. karst shallow tunnel would therefore face high risk of water inrush from surface during the disturbance of construction. In addition, the greater the surface water flow would contribute higher probability of water inrush under the same disaster-causing environment. However, existing research has paid less attention to the influence of surface water flow on faults or fissures water inrush. In this study, a risk assessment system of water inrush in karst shallow tunnel with stable surface water supply was firstly proposed on basis of Qinling Water Conveyance Tunnel and the Yuelongmen Tunnel in China. Each indicator was quantified and classified into four risk levels by the attribute mathematics theory and analytic hierarchy process, the degree of confidence criterion was then applied to identify the risk level of the water inrush. The evaluation results were finally verified by actual scenario on site to confirm the validity of this risk assessment system in karst shallow tunnel with stable surface water supply. Accordingly, the proposed method could be popularized and applied in future tunnel projects, because it could provide safe construction reference for karst shallow overburden tunnel with stable surface water supply.
突水一般对岩溶浅埋隧道施工造成严重影响。由于原地断裂破碎带,风化程度高,岩体质量差。因此,在施工扰动过程中,岩溶浅埋隧道将面临地表突水的高风险。此外,在相同的致灾环境下,地表水流越大,突水概率越大。然而,现有研究较少关注地表水流对断层或裂隙突水的影响。本文以秦岭输水隧道和岳龙门隧道为例,首次提出了地表水供应稳定的岩溶浅埋隧道突水风险评价体系。利用属性数学理论和层次分析法对各指标进行量化,划分为4个风险等级,并应用置信度准则对突水风险等级进行识别。最后通过现场实际场景对评价结果进行验证,验证了该风险评价体系在地表水稳定的岩溶浅埋隧道中的有效性。因此,该方法可在今后的隧道工程中推广应用,为地表供水稳定的岩溶浅覆盖隧道的安全施工提供参考。
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引用次数: 5
Data-driven framework for predicting ground temperature during ground freezing of a silty deposit 粉质沉积物冻结期间地温预测的数据驱动框架
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.3.235
K. Pham, Sangyeong Park, Hangseok Choi, Jongmuk Won
Predicting the frozen zone near the freezing pipe in artificial ground freezing (AGF) is critical in estimating the efficiency of the AGF technique. However, the complexity and uncertainty of many factors affecting the ground temperature cause difficulty in developing a reliable physical model for predicting the ground temperature. This study proposed a data-driven framework to accurately predict the ground temperature during the operation of AGF. Random forest (RF) and extreme gradient boosting (XGB) techniques were employed to develop the prediction model using the dataset of a field experiment in the silty deposit. The developed ensemble models showed relatively good performance (R2 > 0.96), yet the XGB model showed higher accuracy than the RF model. In addition, the evaluated mutual information and importance score revealed that the environmental attributes (ambient temperature, surface temperature, humidity, and wind speed) can be critical in predicting ground temperature during the AFG operation. The prediction models presented in this study can be utilized in evaluating freezing efficiency at the range of geotechnical and environmental attributes.
人工冻结管冻结区预测是评估人工冻结技术效率的关键。然而,影响地温的诸多因素的复杂性和不确定性给建立可靠的地温预测物理模型带来了困难。本研究提出了一个数据驱动的框架,以准确预测AGF运行过程中的地温。采用随机森林(RF)和极端梯度增强(XGB)技术,建立了粉质沉积物野外试验数据的预测模型。所建立的集成模型表现出较好的性能(R2 > 0.96),但XGB模型的精度高于RF模型。此外,评估的互信息和重要性得分表明,环境属性(环境温度、地表温度、湿度和风速)在预测AFG运行期间的地温方面是至关重要的。该预测模型可用于岩土和环境属性范围内的冻结效率评价。
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引用次数: 4
An analytical model for radial consolidation prediction under cyclic loading 循环荷载作用下径向固结预测的解析模型
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.4.333
Monideepa Paul, K. Bakshi, R. Sahu
The excess pore pressure increases under undrained cyclic loading which cause decrease in effective stress followed by possible failure in the soft soil. With the inclusion of vertical drains radial drainage allows quick dissipation of excess pressure during cyclic loading and thereby failure of foundation soil may be avoided. The present study aims for analytical closed-form investigation on soft cohesive deposit under radial flow consolidation through vertical drains with no smear when subjected to long-term rapid cyclic loading. The mathematical formulation of pore pressure including degree of consolidation under cyclic loading is developed by using Green
在不排水循环荷载作用下,超孔隙压力增大,导致软土有效应力降低,进而可能发生破坏。竖向排水管的径向排水管使循环加载时的超压迅速消散,从而避免了地基土的破坏。本研究的目的是对长期快速循环荷载作用下,垂直排水渠径向流固结下无涂抹的软粘性沉积物进行分析封闭研究。利用Green建立了循环荷载作用下含固结度孔隙压力的数学表达式
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引用次数: 1
Force change of the gravel side support during gangue heaping under a new non-pillar-mining approach 一种新的无柱开采方法下矸石堆放过程中碎石侧支架受力变化
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.27.1.031
Jianning Liu, H. Manchao, Hou Shilin, Zhen-chuang Zhu, Yanjun Wang, Jun Yang
The force change characteristics of gravel side support structures during gangue heaping can provide useful information about roadway stability in a new non-pillar-mining approach—noncoal pillar mining with automatically formed gob-side entry (NMAFG). Considering the dynamic shock and static stacking phenomena during gangue heaping, the coefficient of restitution and Janssen model are introduced into the theoretical analysis. Analytical results show that the impact force decreased with increasing gangue heaping height under dynamic shock, while under static stacking, the gangue extrusion force first increased sharply, then increased slowly and stabilized, and the final force was unrelated to the gangue heaping height. Field monitoring was conducted to verify the rationality of the pattern obtained from theoretical analysis. The gangue support structure lateral stress from field monitoring can be divided into two periods. In Period I, the peak value at the lower monitoring point was greater than that at any other point. The lowest sensor was subjected to the greatest impact, at 59.09 kN. In Period II, the stress value first rapidly increased, then slowly increased and stabilized. The final force was unrelated to the gangue height. The sensors at #2 (highest position), #4 (middle position), and #6 (lowest position) measured 31.91 kN, 44.82 kN and 38.19 kN, respectively. The analysis confirmed the variation characteristics of the impact force and extrusion force.
矸石堆置过程中砾石侧支护结构的受力变化特征可以为一种新的非矿柱开采方式——自动形成空边巷道的非煤柱开采巷道稳定性提供有用的信息。考虑矸石堆垛过程中的动冲击和静态堆垛现象,在理论分析中引入了恢复系数和杨森模型。分析结果表明:在动态冲击下,冲击力随矸石堆高的增加而减小,而在静态冲击下,矸石挤压力先急剧增大后缓慢增大并趋于稳定,最终作用力与矸石堆高无关。通过现场监测,验证了理论分析所得模式的合理性。现场监测的矸石支护结构侧向应力可分为两个阶段。周期1,下监测点峰值大于其他监测点峰值。最小的传感器受到的冲击最大,为59.09 kN。在第二阶段,应力值先快速增加,然后缓慢增加并趋于稳定。最终作用力与矸石高度无关。2号(最高位置)、4号(中间位置)和6号(最低位置)的传感器分别测量到31.91 kN、44.82 kN和38.19 kN。通过分析,确定了冲击力和挤压力的变化特征。
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引用次数: 6
Soil consistency and interparticle characteristics of various biopolymer types stabilization of clay 不同生物聚合物类型稳定粘土的土壤一致性和颗粒间特性
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.27.2.103
Zhanbo Cheng, Xueyu Geng
An environmentally friendly improvement method with using biopolymer stabilization of soil has been currently paid more attention for geotechnical engineering practices. And the existing concerns focused on the performance of biopolymers treated clay due to the occurrence of electrical interaction. Therefore, the effect of biopolymer types and water content on the behaviors of biopolymer-clay mixture should be firstly explored in terms of biopolymer applications. In this study, fall cone tests were conducted to evaluate the consistency variations of eight types of biopolymers treated clay, e.g., carrageenan kappa gum (KG), locust bean gum (LBG), xanthan gum (XG), agar gum (AG), guar gum (GG), sodium alginate (SA), gellan gum (GE) and chitosan (CH) at various biopolymer concentrations (e.g., between 0.1% to 5% biopolymer to soil mass ratio). The results indicated that neutral biopolymers (e.g., LBG and GG) significantly caused the increase of liquid limit and undrained shear strength regardless of biopolymer concentration. And the liquid limit and undrained shear strength of negative charged biopolymers (e.g., KG, SA, GE and XG) treated clay decreased firstly following increased, while AG and CH had limit effect on soil consistency. In addition, the trend of plasticity index was similar to liquid limit altering the USCS classification of biopolymer treated clay as silt or clay. Moreover, empirical equations determining undrained shear strength and shear viscosity of biopolymer-treated clay were also established.
利用生物聚合物稳定土体的环境友好型改良方法目前已受到岩土工程实践的广泛关注。现有的关注主要集中在生物聚合物处理粘土后由于电相互作用的发生而产生的性能。因此,在生物聚合物的应用方面,应首先探索生物聚合物类型和含水量对生物聚合物-粘土混合物行为的影响。在本研究中,进行了落锥试验,以评估8种生物聚合物处理过的粘土,如卡拉胶卡帕胶(KG)、槐豆胶(LBG)、黄原胶(XG)、琼脂胶(AG)、瓜尔胶(GG)、海藻酸钠(SA)、结冷胶(GE)和壳聚糖(CH)在不同生物聚合物浓度下(例如,生物聚合物与土壤质量比在0.1%至5%之间)的稠度变化。结果表明,中性生物聚合物(如LBG和GG)无论浓度如何,都能显著提高液限和不排水剪切强度。负电荷生物聚合物(KG、SA、GE和XG)处理粘土的液限和不排水抗剪强度先减小后增大,AG和CH对土壤稠度有限制作用。此外,塑性指数的变化趋势与液限相似,改变了生物聚合物处理粘土的USCS分类为粉砂或粘土。此外,还建立了生物聚合物处理粘土的不排水剪切强度和剪切粘度的经验方程。
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引用次数: 4
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Geomechanics and Engineering
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