Reinforcement Technology for Soft Soil Roadbed in the Widened Section of Expressway Expansion

This article examines the soft soil roadbed reinforcement technology for widened sections of highways in a specific project.It provides an overview of the project,the principles of soft soil roadbed reinforcement technology for wide sections,and its practical application.The analysis aims to offer guidance on applying soft soil roadbed wide section reinforcement technology and enhancing the overall quality of similar projects.

基于soft-soil轮胎的自行火炮动态响应仿真研究

为掌握某型自行火炮在几种典型软土地面上的行驶与射击动态响应规律,探索前轮车辙对后轮的影响,基于多体系统动力学软件ADAMS和有限元软件ABAQUS,建立自行火炮刚柔耦合行驶与射击动力学模型。使用soft-soil轮胎模型,考虑各种土壤的弹塑性、承压特性、剪切特性和轮胎变形等因素,全面分析火炮行驶与行进间射击关键位置的动态响应,得到相比于不考虑前后轮车辙影响的区别和特点。获得更加真实的考虑了地面环境的结论,进一步为作战地面参数化构建技术以及车辆振动干扰研究等提供参考依据。

Vacuum preloading combined electroosmotic strengthening of ultra-soft soil

To assess the effectiveness of vacuum preloading combined electroosmotic strengthening of ultra-soft soil and study the mechanism of the process,a comprehensive experimental investigation was performed.A laboratory test cell was designed and applied to evaluate the vacuum preloading combined electroosmosis.Several factors were taken into consideration,including the directions of the electroosmotic current and water induced by vacuum preloading and the replenishment of groundwater from the surrounding area.The results indicate that electroosmosis together with vacuum preloading improve the soil strength greatly,with an increase of approximately 60%,and reduce the water content of the soil on the basis of consolidation of vacuum preloading,however,further settlement is not obvious with only 1.7 mm.The reinforcement effect of vacuum preloading combined electroosmosis is better than that of electroosmosis after vacuum preloading.Elemental analysis using X-ray fluorescence proves that the soil strengthening during electroosmotic period in this work is mainly caused by electroosmosis-induced electrochemical reactions,the concentrations of Al2O3in the VPCEO region increase by 2.2%,1.5%,and 0.9%at the anode,the midpoint between the electrodes,and the cathode,respectively.

Influence of sand content on the flow characteristics of soft soil under cyclic and high-frequency vibration

The flow characteristics of foundation soils subjected to train loads can present engineering hazards in highspeed railways. In order to verify the feasibility of blending coarse sand in modifying soft subsoil, undrained pulling sphere tests were carried out and the train loads were simulated through localized and cyclic vibration at various frequencies. Laboratory testing results indicate that the fl ow characteristics of soft soil can be signifi cantly enhanced by high-frequency vibration;meanwhile the continuous increase in fl ow characteristics caused by cyclic vibration may be an important reason for the long-term settlement of soft subsoil. The infl uence of sand content on fl ow characteristics is also studied in detail, and it is shown that the addition of coarse sand can weaken the fl ow characteristics of soft soil induced by sudden vibration at lower than 50 Hz. Under the condition of cyclic vibration, the growth of the fl ow characteristics of sand-clay mixtures is mainly caused by the fi rst-time vibration in the cycle, and the increase in sand content can make the fl ow characteristics present a faster convergent tendency.

Collapse of a Deep Excavated Foundation Pit in the Soft Soils by 3-D FEM

In view of the collapse of a deep excavated foundation pit of the Xianghu subway underground station in Hangzhou of China,the main features of the accident are analyzed,and the induced factors of the accident are summarized. Then,a 3-D FEM analysis model is created to demonstrate the soil-support structures interaction system,and the effect of the main factors,such as the volume replacement ratio of the bottom soil reinforcing,the asymmetric ground overload,the embedded depth of the diaphragm wall,the shear strength of the bottom soils disturbed by the construction,and the excessive excavation of the bottom soil,are analyzed and compared. The results show that the ineffective original reinforcement plan for the bottom soft soil is the most prominent factor for the accident,and the disturbance effect of the deep excavation on the shear strength of the bottom soft soil is another significant factor for the accident. Meanwhile,if the reinforcement of the bottom soft soil is canceled,an appropriate extension of the diaphragm retaining walls to the under lying harder soil layer can also effectively prevent the collapse of the deep excavated foundation pit. In addition,the partly excessive excavation in the process has a great influence on the axial force of the most nearby horizontal support but few effect on the stability of the diaphragm wall. Thus,the excessive excavation of the bottom soils should not be the direct inducing factor for the accident. To the asymmetric ground overload,it should be the main factor inducing the different damage conditions of the diaphragm walls on different sides. According to the numerical modeling and actual engineering accident condition,the development process of the accident is also identified.

Review of research on high-speed railway subgrade settlement in soft soil area

Construction issues of high-speed rail infrastructures have been increasingly concerned worldwide,of which the subgrade settlement in soft soil area becomes a particularly critical problem.Due to the high compressibility and low permeability of soft soil,the post-construction settlement of the subgrade is extremely difficult to control in these regions,which seriously threatens the operation safety of high-speed trains.In this work,the significant issues of high-speed railway subgrades in soft soil regions are discussed.The theoretical and experimental studies on foundation treatment methods for ballasted and ballastless tracks are reviewed.The settlement evolution and the settlement control effect of different treatment methods are highlighted.Control technologies of subgrade differential settlement are subsequently briefly presented.Settlement calculation algorithms of foundations reinforced by different treatment methods are discussed in detail.The defects of existing prediction methods and the challenges faced in their practical applications are analyzed.Furthermore,the guidance on future improvement in control theories and technologies of subgrade settlement for high-speed railway lines and the corresponding challenges are provided.

Earthquake response of wrap faced embankment on soft clay soil in Bangladesh

A wrap-faced embankment model on soft clay soil subjected to earthquake motion was investigated in this study.The study was conducted both experimentally using a shaking table and numerically using PLAXIS 3D software.The amplification of acceleration,displacement,pore water pressure,and strain response were measured while varying input accelerations and surcharge pressures.Time histories of the Kobe record of the 1995 Hanshin earthquake were used as the input seismic motion.The input acceleration was 0.05 g,0.1 g,0.15 g,and 0.2 g,and different surcharge pressures were 0.70 kPa,1.12 kPa,and 1.72 kPa with relative density of Sylhet sand fixed to 48%.The output data from the shaking table tests and the numerical analysis performed through the PLAXIS 3D software were compared,and these findings were also compared with some earlier similar studies.The acceleration amplification,displacement,pore water pressure,and strain(%)changed along the elevation of the embankment and acceleration response increased with the increase in base acceleration.The increase was more noticeable at higher elevations.These findings enrich the knowledge of predicting the dynamic behavior of wrap-faced embankments and enable the design parameters to be adjusted more accurately.

Engineering Geological Zoning of Soft-Soil Foundation Based on Combination Weighting and Extension Methods

Different criteria and factors are used in different methods of soft soil foundation settlement calculation and engineering geological zoning.The methods used are not universally suitable for complex geological environments.The post-construction settlement of soft soil foundations are especially large and difficult to calculate.In addition,there are many deficiencies in the current methods used for engineering geological zoning.Focusing on the need of establishing engineering geological zoning for areas with soft soil foundations in the Tianjin Marine Economic Area,combination weighting and extension methods were introduced.An evaluation model for the settlement of soft soil foundations was established using multiple factors and large amounts of data.This evaluation model is accurate and objective for delineating engineering geological zoning.These methods eliminate deficiencies by considering both objective and subjective factors,and help obtain an objective and accurate result.

Prediction of compaction parameters for fine-grained soil: Critical comparison of the deep learning and standalone models

A comparison between deep learning and standalone models in predicting the compaction parameters of soil is presented in this research.One hundred and ninety and fifty-three soil samples were randomly picked up from two hundred and forty-three soil samples to create training and validation datasets,respectively.The performance and accuracy of the models were measured by root mean square error(RMSE),coefficient of determination(R2),Pearson product-moment correlation coefficient(r),mean absolute error(MAE),variance accounted for(VAF),mean absolute percentage error(MAPE),weighted mean absolute percentage error(WMAPE),a20-index,index of scatter(IOS),and index of agreement(IOA).Comparisons between standalone models demonstrate that the model MD 29 in Gaussian process regression(GPR)and model MD 101 in support vector machine(SVM)can achieve over 96%of accuracy in predicting the optimum moisture content(OMC)and maximum dry density(MDD)of soil,and outperformed other standalone models.The comparison between deep learning models shows that the models MD 46 and MD 146 in long short-term memory(LSTM)predict OMC and MDD with higher accuracy than ANN models.However,the LSTM models outperformed the GPR models in predicting the compaction parameters.The sensitivity analysis illustrates that fine content(FC),specific gravity(SG),and liquid limit(LL)highly influence the prediction of compaction parameters.

Non-destructive experimental testing and modeling of electrical impedance behavior of untreated and treated ultra-soft clayey soils

The characterization of ultra-soft clayey soil exhibits extreme challenges due to low shear strength of such material.Hence,inspecting the non-destructive electrical impedance behavior of untreated and treated ultra-soft clayey soils gains more attention.Both shear strength and electrical impedance were measured experimentally for both untreated and treated ultra-soft clayey soils.The shear strength of untreated ultra-soft clayey soil reached 0.17 kPa for 10% bentonite content,while the shear strengths increased to 0.27 kPa and 6.7 kPa for 10% bentonite content treated with 2% lime and 10% polymer,respectively.The electrical impedance of the ultra-soft clayey soil has shown a significant decrease from 1.6 kΩ to 0.607 kΩ when the bentonite content increased from 2% to 10% at a frequency of 300 kHz.The10%lime and 10% polymer treatments have decreased the electrical impedances of ultra-soft clayey soil with 10%bentonite from 0.607 kΩ to 0.12 kΩ and 0.176 kΩ,respectively,at a frequency of 300 kHz.A new mathematical model has been accordingly proposed to model the non-destructive electrical impedancefrequency relationship for both untreated and treated ultra-soft clayey soils.The new model has shown a good agreement with experimental data with coefficient of determination（R;）up to 0.99 and root mean square error（RMSE） of 0.007 kΩ.

焚烧飞灰-水泥协同处置软土冻融与干湿循环下强度及环境耐久性分析

焚烧飞灰的处置成为社会越来越关心的热点,实现其资源化是当下研究的热门。以广西某填埋场的生活垃圾焚烧飞灰为主要研究对象,对标准养护条件下飞灰-水泥-软土体系进行干湿及冻融循环处理,通过无侧限抗压强度试验、翻转振荡试验及酸中和试验探究飞灰-水泥土的强度、环境及耐久性。结果表明,掺加飞灰的试样养护完毕均能满足二级公路基层强度要求,3种配合比下的试样质量损失良好,并呈现较强的酸缓冲能力。通过水平振荡毒性测试,对目标重金属Pb, Cu和Cd的释放毒性进行探究,低于地下水Ⅳ类水限值,环境影响较小,最后对飞灰用于道路路基加固的经济和社会效益进行评估,较可观。

A 3D Numerical Simulation of Sand Drain Element in the Soft Soil of Guangzhou-Zhujiang Highway,China

The behavior of sand drain was estimated so that the size of very large load-pressure could be eliminated by changing the configuration of the sand drain elements into sand wall.A 3D mathematical model was formulated to transform the configuration of a sand drain into a sand wall to minimize or eliminate the excessive stress and primary settlement on the road base.This was barely considered in the past. According to soil mechanics theory and seepage characteristics of sand drain in road base foundations, a 3D sand drain element in FEM format was generated,and a matrix expression was formulated which was introduced into 3D Biot Consolidation

矿渣-水泥与磷石膏-水泥固化软土力学特性对比研究

为优化工业废渣在软土固化中配置,选用磷石膏与矿渣替代部分水泥,通过无侧限抗压强度与海水浸泡试验对比分析初始含水率、工业废渣掺量、养护龄期及海水侵蚀对工业废渣-水泥固化土强度特性影响。结果表明:磷石膏-水泥固化土抗压强度随养护龄期延长而提高,随磷石膏掺量和初始含水率增加而降低;矿渣-水泥固化土抗压强度随养护龄期延长而提高,更适应较高初始含水率软土,随初始含水率及矿渣掺量先增加后减小。海水浸泡后,磷石膏-水泥固化试样因磷石膏掺量增加更易遭受侵蚀,表现为更严重的开裂现象与强度损失;矿渣-水泥固化软土更耐受海水侵蚀,各掺量下固化试样均未开裂,且海水浸泡导致的强度损失随矿渣掺量增加呈减小趋势。

Numerical Comparative Study on the Effective Replacement Thickness of Traditional Stone Coarse Aggregate or Steel-Slag Aggregate Mixtures in Improved Soft Fine Soils

This study uses Steel Slag Coarse Aggregate (SSCA) as a mixture replacement, preamble material to improve soft soils, which is economic, and has good effect environment. Recently, the development and utilization of by-product, waste and recycle materials must be studied and investigated as a source of improved material for soft soils as, an economic and good effect environmental. The study analyzes effects of both replaced mixtures, (SSCA) or (TSCA) on improved soil bearing capacity and expected settlement after verifying the model. Numerical modeling of the one of real store loaded strip using, PLAXIS, 2D, strain deformation behavior to achieve field visible and measured deformations of untreated soft soil. Numerical studies were devolved to investigate geomechanics parameters improved to compare between using (SSCA) or (TSCA) as, replacement mixture. Results demonstrate that using (SSCA) improved compressibility and strength of shallow soft soil layer significantly than using (TCSA) mixture, while (SSCA) improved strip footing ultimate bearing capacity, (UBC), by 84.4% compared with increase of 20.5% when using (TCSA) mixture at the same thickness. In addition, the study highlights the effective (SSCA) replacement thickness ranges between (0.65 ~ 0.80) footing width.

Soft soil Treatment for Large Coal-fired Power Plant

This paper describes the engineeringapplication of soil improvement in manylarge coal-fired power plants designed byEast China Electric Power Design Institute.Soil improvement technology is especiallysuitable for strengthening soft soil. Exceptfor increasing soil bearing capacity andcontrolling soil deformation, it can also beused to eliminate loose sand liquefactionunder seismic loading, or to strengthen slopestability. The applications introduced in thispaper include dynamic consolidation,drained consolidation, stone pile, soil-cement mixed pile, jet grouting andcompacting grouting, reinforced earth, etc.The kinds of soil layer to be improvedinclude typical Shanghai soft soil, loose siltand silt sand, miscellaneous fill andhydraulic filled soil. As a result of thetreatments described in this paper, nobuilding fissures caused by soil differentialsettlement had ever occurred in the powerplants engineered by ECEPDI andconstructed in 1990s.

双排桩-锚索支护体系在软土地区基坑中的应用

为研究双排桩-锚索结构在软土基坑中的内力变化规律及可行性,本文通过理论计算及数值模拟,以东莞某软土基坑工程为例,对结构水平位移、弯矩等参数的变化规律进行了研究,并将实测值与计算值进行了对比。结果表明,卸荷板可提供一个反弯矩,增加结构稳定性;支护结构水平位移理论及数值计算曲线与实测曲线变化趋势基本相似,变形值均在规范允许范围之内;双排桩-锚索结合卸荷板体系应用于场地受限的软土地区基坑支护效果较好。

Response of Surface Soft Soil and Fine-Grained Sand Layers to Seismic Waves

Shanghai is located in eastern China and is built on overburden soil layers. It can be seen from the Mexico M S=8.1 earthquake on September 19, 1985 and the Hanshin M S=7.4 earthquake on January 17,1995 that heavy casualties and property losses have a direct relationship with overburden soil layers. Ground motions caused by earthquakes are significantly amplified when passing through the soil layers. Under the influence of these amplified motions, building structures, whose nature frequency is within the frequency band of soil amplification response, will experience more severe damage than those built on bedrock. Therefore, engineering seismologists have paid considerable attention the amplification responses in the Shanghai overburden soil layers. The amplification responses of soil and sand layers in this paper are given by the M L=4.1 earthquake in Nantong, Jiangsu Province on December 25, 2001 at 31.8° N, 120.9° E. It can be seen that the responses of soil and sand layers are very different. That is important.

基于GA-BP神经网络的软土路基运营期沉降预测

为了实现高速公路软土路基沉降的准确预测,采用遗传算法(GA)优化BP神经网络,研究3种输入对预测结果精度的影响.选取时间t以及其15 d前的沉降量S_(t-15)和平均沉降速率v_(t-15)为影响因素,在t、t-S_(t-15)、t-S_(t-15)-v_(t-15)三种输入下,分别取某高速公路软土路基运营期实测沉降数据的前50%、80%为训练集,余下原始数据为测试集,重复训练10次后取平均值作为输出值.采用决定系数(R^(2))来判别模型拟合度,均方根误差(RMSE)和平均绝对百分比误差(MAPE)作为模型性能的评价指标.结果表明:3种输入的R^(2)均大于0.99;训练集占原始数据的比例为50%时,t-S_(t-15)输入的预测误差最小,RMSE为1.31 mm,MAPE为4.71%;训练集占原始数据的比例为80%时,t-S_(t-15)-v_(t-15)输入的预测误差最小,RMSE为0.29 mm,MAPE为1.00%.t、t-S_(t-15)、t-S_(t-15)-v_(t-15)三种输入都可对路基沉降进行预测,其中t-S_(t-15)-v_(t-15)输入下取实测沉降数据的80%作为训练集时预测结果最精确.

电石渣-草木灰复合固化剂固化废弃软土微观特性研究

为确定电石渣-草木灰复合固化剂最优配比,并揭示初始含水量(w_(0))、有机质含量(w_(c))、固化剂掺量(w_(g))和龄期(T)四种因素对固化废弃软土(简称固化土)力学性质影响的微观机理,以废弃软土为研究对象,采用PSO-SVM模型预测固化剂的最优配比(电石渣∶草木灰=1∶1.2),基于此,开展不同w_(0)、w_(g)、w_(c)和T下固化土的电镜扫描试验,利用图像处理软件研究固化土丰度(C_(r))、圆形度(R)和分形维数(D)受w_(0)、w_(g)、w_(c)和T的影响规律,通过X射线衍射试验分析了废弃软土、电石渣、草木灰以及固化土的矿物成分。结果发现:碱性环境下,电石渣与草木灰发生火山灰反应,生成大量的针状固化产物(C-S-H胶体)和少部分钙矾石,提高了软土结构的密实性;w_(0)和w_(c)的增加会抑止固化剂的水化,增加固化土结构的分散性,进而减小固化土的R值,提高固化土的D值;而w_(g)和T促进了固化反应的发展,增加了扁圆状固化产物的产生,提高了固化土结构的密实性,四种因素中,T对固化土的R和D影响最为显著。

Fractional description of mechanical property evolution of soft soils during creep

The motion of pore water directly influences mechanical properties of soils, which are variable during creep. Accurate description of the evolution of mechanical properties of soils can help to reveal the internal behavior of pore water. Based on the idea of using the fractional order to reflect mechanical properties of soils, a fractional creep model is proposed by introducing a variable-order fractional operator, and realized on a series of creep responses in soft soils. A comparative analysis illustrates that the evolution of mechanical properties, shown through the simulated results, exactly corresponds to the motion of pore water and the solid skeleton. This demonstrates that the proposed variable-order fractional model can be employed to characterize the evolution of mechanical properties of and the pore water motion in soft soils during creep. It is observed that the fractional order from the proposed model is related to the dissipation rate of pore water pressure.