Prediction of high-embankment settlement combining joint denoising technique and enhanced GWO-v-SVR method

Reliable long-term settlement prediction of a high embankment relates to mountain infrastructure safety.This study developed a novel hybrid model(NHM)that combines a joint denoising technique with an enhanced gray wolf optimizer(EGWO)-n-support vector regression(n-SVR)method.High-embankment field measurements were preprocessed using the joint denoising technique,which in-cludes complete ensemble empirical mode decomposition,singular value decomposition,and wavelet packet transform.Furthermore,high-embankment settlements were predicted using the EGWO-n-SVR method.In this method,the standard gray wolf optimizer(GWO)was improved to obtain the EGWO to better tune the n-SVR model hyperparameters.The proposed NHM was then tested in two case studies.Finally,the influences of the data division ratio and kernel function on the EGWO-n-SVR forecasting performance and prediction efficiency were investigated.The results indicate that the NHM suppresses noise and restores details in high-embankment field measurements.Simultaneously,the NHM out-performs other alternative prediction methods in prediction accuracy and robustness.This demonstrates that the proposed NHM is effective in predicting high-embankment settlements with noisy field mea-surements.Moreover,the appropriate data division ratio and kernel function for EGWO-n-SVR are 7:3 and radial basis function,respectively.

Settlement Control Technology of High Filled Soil-Rock Embankment in Alpine and High-Altitude Areas

China's infrastructure has gradually achieved large-scale development,and transportation construction has also shifted from east to west,transitioning from plains to mountainous areas.High-fill embankments of different sizes in mountainous areas are unavoidable,and the settlement of high-fill embankments is usually the most concerned issue in high-fill projects.According to the current research of highway projects,most of the high embankments in mountainous areas are soil-rock mixed embankments or rock-filled embankments,and their post-construction settlements are directly related to construction technology and the type of filler used.In this paper,the problems in the settlement control of earth-filled embankment and related factors are analyzed in detail.The settlement control technology of high-fill embankment in high-cold and high-altitude areas is also discussed,so as to ensure the overall quality of high-fill embankment.

Mechanism and calculation method of rheological settlement of high-filled embankment

The characteristics of high-filled embankment rheological settlement were analyzed;mechanical calculation model of high-filled embankment rheological settlement during constructing and running period was also put forward.Combining the macroscopic and microscopic deformation properties of the engineering soil grain,its constitutive model was set up and its characters were fully revealed,at the same time,its practical calculation formula under the action of dead-weight load was derived,which is feasible by analysis and comparison.

Model tests on XCC-piled embankment under dynamic train load of high-speed railways

Piled embankments,which offer many advantages,are increasingly popular in construction of high-speed railways in China.Although the performance of piled embankment under static loading is well-known,the behavior under the dynamic train load of a high-speed railway is not yet understood.In light of this,a heavily instrumented piled embankment model was set up,and a model test was carried out,in which a servo-hydraulic actuator outputting M-shaped waves was adopted to simulate the process of a running train.Earth pressure,settlement,strain in the geogrid and pile and excess pore water pressure were measured.The results show that the soil arching height under the dynamic train load of a high-speed railway is shorter than under static loading.The growth trend for accumulated settlement slowed down after long-term vibration although there was still a tendency for it to increase.Accumulated geogrid strain has an increasing tendency after long-term vibration.The closer the embankment edge,the greater the geogrid strain over the subsoil.Strains in the pile were smaller under dynamic train loads,and their distribution was different from that under static loading.At the same elevation,excess pore water pressure under the track slab was greater than that under the embankment shoulder.

Dynamic responses of bridge-approach embankment transition section of high-speed rail

Based on the vehicle track coupling dynamics theory, a new spatial dynamic numerical model of vehicle track subgrade coupling system was established considering the interaction among different structural layers in the subgrade system. The dynamic responses of the coupled system were analyzed when the speed of train was 350 km/h and the transition was filled with graded broken stones mixed with 5% cement. The results indicate that the setting form of bridge-approach embankment section has little effect on the dynamic responses, thus designers can choose it on account of the practical circumstances. Because the location about 5 m from the bridge abutment has the greatest deformation, the stiffness within 0 5 m zone behind the abutment should be specially designed. The results of the study from vehicle track dynamics show that the maximum allowable track deflection angle should be 0.09% and the coefficient of subgrade reaction(K30) is greater than 190 MPa within the 0 5 m zone behind the abutment and greater than 150 MPa in other zones.

Analysis of the Influence Factors of Differential Settlement of High Embankment in Mountain Area

This paper reveals and analyses various influence factors which cause differential settlement of high embankment in mountain area using indoor consolidation test and field loading test. In this research, the actual stress characteristics of high embankment are simplified, stability compression value of stuffing with loads under lateral restricted conditions can be measured, e-p curves and p-s curves are drawn, we can calculate compression modulus as computation criteria to estimate the settlement of high embankment. The results indicate that unconsolidated flow of high embankment is the main factor to cause differential settlement of high embankment in mountain area. As the soil consolidated, compressive deformation and the strength gradually increase, the bearing capacity of the foundation is enhanced to reduce differential settlement of the post-construction of high embankment.

Dynamic compaction treatment technology research of red clay soil embankment in southern mountains

High liquid limit soil generally adopted in expressway embankment construction of southern mountains, which often expresses some characteristics including high moisture content, high porosity ratio, low permeability, high compressibility, certain disintegration, and so on. Spring soil phenomenon and inhomogeneous compaction have effects on the quality of embankment construction, just because the water in soil is difficult to evaporate. Based on the study of reinforcement mechanism for high liquid limit soil, in situ tests for dynamic compaction treatment in Yizhang-Fengtouling expressway embankment were developed. The reliable and economical dynamic compaction treatment methods and the construction technology for large range high liquid limit soil embankment in southern mountains expressway were discussed. In the process, convenient measurement methods were adopted to evaluate the treatment effects. The test results show that the dynamic compaction method has good treatment effects on the local red clay embankment. The embankment compaction degree is improved with compactness coming to 90% around tamping pits and compactness over 95% in tamping pits interior after tamping. The bearing capacity, the physical mechanic-property and the shear strength for soil are obviously improved, which are enhanced with cohesive strength increasing over 10 kPa and compression modulus increasing over 3 MPa.

Probabilistic analysis of embankment slope stability in frozen ground regions based on random finite element method

Prediction on the coupled thermal-hydraulic fields of embankment and cutting slopes is essential to the assessment on evolution of melting zone and natural permafrost table, which is usually a key factor for permafrost embankment design in frozen ground regions. The prediction may be further complicated due to the inherent uncertainties of material properties. Hence, stochastic analyses should be conducted. Firstly, Karhunen-Loeve expansion is applied to attain the random fields for hydraulic and thermal conductions. Next, the mixed-form modified Richards equation for mass transfer （i.e., mass equation） and the heat transport equation for heat transient flow in a variably saturated frozen soil are combined into one equation with temperature unknown. Furthermore, the finite element formulation for the coupled thermal-hydraulic fields is derived. Based on the random fields, the stochastic finite element analyses on stability of embankment are carried out. Numerical results show that stochastic analyses of embankment stability may provide a more rational picture for the distribution of factors of safety （FOS）, which is definitely useful for embankment design in frozen ground regions.

基于协同降噪与IGWO-SVR的高填方路基沉降预测

高填方路基沉降影响山岭重丘区重载铁路运营安全。为克服实测沉降数据掺杂随机噪声、现有预测模型适用性差的不足,提出基于协同降噪算法与IGWO-SVR模型的沉降预测方法。运用互补集合经验模态分解法(CEEMD)与小波包变换法(WPT)对含噪沉降数据进行协同降噪处理;提出基于佳点集初始化均布、非线性收敛控制与自身历史最优记忆位置更新的改进灰狼优化(IGWO)算法,并结合支持向量回归模型(SVR),构建IGWO-SVR沉降预测模型。进一步地,利用大准铁路工点及现有文献研究成果,验证IGWO-SVR模型的优越性。结果表明:协同降噪法可有效消除原数据中噪声项的干扰波动;在小样本数据集上,IGWO-SVR模型较传统沉降预测模型与现有文献所述预测模型,具有更高的预测精度与稳定性。研究成果为重载铁路高填方路基沉降预测提供了新途径。

某高速公路高填路堤滑坡成因及稳定性分析

山区地形复杂多变,进行路线设计时,洼地、沟谷位置多设计为填方路堤。雨季时,此类地段为地表水汇集处,排水对于公路运营期路堤安全而言至关重要。文章分析了一种由于地表水排水不畅导致路堤破坏的案例,该案例在丘陵山区较为常见。根据路堤后缘裂缝和路堤坡体、坡脚等剪出口裂缝、鼓胀位置推测潜在滑动面,并对各种工况的稳定性进行了定量计算。研究方法可为公路路堤边坡水毁破坏初期的应急抢险提供稳定性分析支持。

高填方路堤滑坡成因分析及防护对策

以某高速公路互通匝道高填方路堤边坡失稳为例,综合考虑填方区原始地形地貌、地层岩性及施工工艺对路堤边坡稳定性的影响,分析了土−岩二元结构填方边坡的变形特征和破坏机理,认为岩土界面可能为填方边坡的最薄弱层面而非填筑界面。同时,根据滑坡成因分析和稳定性评价结果,借助ABAQUS有限元分析软件对填方边坡的破坏机理做了进一步验证,并对抗滑桩支挡结构的受力状态进行了数值分析。分析可知,滑坡滑面主要在岩土界面处,滑面形态呈折线状;通过开挖台阶、设置宽平台和抗滑桩支挡可有效抑制路堤边坡变形,同时应加强排水;在抗滑桩支挡作用下,高填方路堤边坡潜在滑动面表现为由深层向浅层的演化破坏;滑动面以上桩身应力逐渐减小,在滑面处形成“三角状”高应力区,滑动面以下桩−土接触段桩身应力主要集中在桩前;桩身主要受弯段在潜在滑面以下;桩身主要受推力部位在滑面以上桩长1/5~1/3处,而主要抗力部位在滑面以下桩前部分。

高速铁路路堤对环境振动的影响研究

为研究高速铁路路堤填高、坡率对环境振动的影响,在京张高速铁路路基段附近开展现场实测,研究其环境振动的传播衰减规律。基于现场实测结果利用FLAC3D建立数值仿真模型,数值分析结果与实测值吻合良好,验证模型的合理性,并进行路堤填高、坡率对环境振动影响的分析。结果表明:现场实测振级幅值均小于63 dB,整体而言测点振级随着测点与线路外轨距离的增加逐渐减小;当路堤高度为1 m时,相对于路堤高度为0 m测点在距铁路线距离60 m范围以内振级出现反弹放大的现象;当路堤高度大于2 m时,相对于路堤高度为0 m对环境振动的影响大;因此,建议路堤高度在设定时不小于2 m;当边坡直立时地表振动最小;当坡率大于0时,相对于边坡直立时对环境振动的影响大;因此,建议采用U型槽结构路堤,其对环境振动的影响较小。

服役条件下高铁路基桩网结构土工格栅张拉试验研究

桩网结构路基已经在软土地区的高速铁路建设中取得了广泛的应用,服役期地基过大沉降、地下水淹没桩顶等引起桩网结构不合理受力,甚至导致格栅张拉破坏,目前仍缺乏深入的针对性观测和分析。建立一个全比尺的桩网结构路基模型试验,开展正常路基、桩间土过大沉降、路基浸水和路基水位下降4组典型工况的试验。同时采用前期研发的高速铁路路基动力效应试验装置施加车速达360 km/h、轴重为17 t和25 t的列车移动荷载,利用沉降板加位移传感器测量桩土的沉降变形量,利用光纤传感器测定了每组工况下的格栅拉力变化和空间分布规律,研究不同工况下相同的列车长期荷载对土工格栅拉力的影响。试验结果表明:在列车荷载作用下正常路基的桩网结构格栅最大拉力为5.9 kN/m,位于桩帽边缘处,为格栅抗拉强度的11.8%;桩间土发生过大沉降后格栅拉力最大值仍位于同一位置即桩帽边缘处,为11.85 kN/m,为格栅抗拉强度的23.7%。水位上升后桩网结构格栅拉力下降,但在列车荷载作用下格栅拉力又迅速增长,最大拉力为12 kN/m,水位下降后在列车荷载作用下格栅最大拉力为10.5 kN/m。桩网结构路基的规范设计中对格栅拉力的计算偏于保守,模型试验结果对实际工程中桩网结构路基的设计以及理论方法的验证有一定的指导和借鉴意义。

膨胀土高填方渠堤沉降变形特征研究

南水北调中线工程膨胀土高填方渠堤的工后稳定性是各方关注的焦点,如果渠堤工后沉降大,易导致衬砌面板结构内力变化,影响渠道的运行安全。针对南水北调中线某膨胀土高填方渠堤工后沉降明显的问题,通过该段渠堤现场表面变形、内部变形、地下水位和降雨量监测数据的分析,对其沉降变形特征进行了研究。结果表明:高填方渠堤中渠基膨胀土的垂直表面位移受降雨影响显著,其导致高填方渠堤沉降变形随时间的变化可分为缓降段、陡降段、回弹-稳定-陡降段和回弹段4个阶段;填方高度对渠堤的表面变形和内部变形均存在显著影响,渠堤沉降量随着填方高度的减小而逐渐减小,同时,渠堤内部变形主要集中在孔口以下6~7 m的深度范围内,且指向渠外方向累计水平位移量较大于指向渠内方向的累计水平位移量;结合测压管水位、垂直位移测点及降雨量的变化规律,得到了该段渠基土的表面变形与测压管水位存在较强的相关性,地下水位变化是导致区域地表变形的主要因素。研究成果对膨胀土高填方渠堤工后沉降防治具有科学的参考意义。

高铁荷载下路堤和路堑段地面振动特性现场测试与数值分析

对巴黎-布鲁塞尔高速铁路地面振动开展现场测试,对比分析了高铁运行引起的路堤和路堑段地面振动特性以及传播衰减规律。基于2.5维有限元法基本原理,推导并建立了高铁荷载下路堤和路堑段2.5维有限元动力计算模型,详细讨论了路堤和路堑设计参数对地面振动特性的影响。结果表明:距轨道较近处的地面振动幅值主要受列车轴重影响,而距轨道较远处则由中间车相邻转向架轮对的叠加效应主导。高铁运行引起的路堤和路堑段地面振动随与轨道距离增加而减小,中高频成分振动的衰减速率显著大于其他频段。路堤和路堑段地面振动1阶主频主要由列车荷载的基频f_1主导,随车速提高逐渐向高频方向移动。路堤和路堑对地面振动的衰减规律有重要影响,路堤段地面振动随与轨道间距的衰减过程可分为两个阶段,而路堑段地面振动衰减过程则可分为三个阶段,且振动在堑顶处有较为明显的局部放大现象。当与路堤段轨道间距≥19.0 m(路堑段≥23.0 m)后,地面振动Z振级VL_Z均小于80.0 dB。同时,高铁荷载下地面振动随路堤高度或路堑深度的增加而减小,当超过某一限值时,继续增加路堤高度或路堑深度难以有效减小地面振动。路堤段地面振动随路堤弹性模量的增大而减小。此外,在确保稳定性的前提下,较陡的路堑边坡更有利于减小高铁运行引起的地面振动。

基于DS证据理论与综合赋权改进可拓法的黄土区重载铁路高填方路基服役性能评价

为有效评价黄土区重载铁路高填方路基的变形与稳定状态,在重载铁路高填方路基服役性能初选评价指标库基础上,通过基于证据可信度的DS证据理论融合指标的重要度、独立度与区分度3项特征值,构建重载铁路高填方路基服役性能优选指标体系;基于综合赋权改进可拓评价法,建立针对重载铁路高填方路基服役性能的多层次综合评价模型,并利用该模型对大准及巴准铁路两段高填方路基服役性能进行评价。研究结果表明,上述两段高填方路基服役性能等级评价结果依次为差与良,并均通过了有效性检验;本文研究所提方法较云模型更能准确评价高填方路基服役性能,且比《铁路路基大维修规则》更能全面客观地反映高填方路基服役性能所处状态。研究结果可为黄土区重载铁路高填方路基服役性能状态评价提供参考。

高速铁路红层改良填料路堤动力特性及沉降规律研究

川渝地区高速铁路建设频繁跨越红层地区,为高速铁路的建设和运营带来了新的风险和隐患。为了解决红层土工程适应性差的问题,对红层土试样展开室内土工试验,并且基于改良土工程参数构建了高速铁路红层改填料路堤动力学模型,分析了高速列车荷载下路堤内动应力、动位移、加速度的变化规律并提出质量控制措施。期望研究成果为红层地区高速铁路路基设计和施工提供理论指导与实践经验。

含水量对膨胀土高填方渠堤土体剪切特性的影响研究

通过不同含水量下南水北调中线工程高填方渠堤的改性土、膨胀土和渠基土的直剪试验,研究含水量对3种土体剪应力-剪切位移以及抗剪强度的影响规律。结果表明:3种土体的基质吸力随着含水量增加而显著减小;当含水量较低时,剪应力-剪切位移曲线呈剪切软化型;而随含水量的增加,剪应力-剪切位移曲线转化为剪切硬化型。不同土体的抗剪强度随含水量增加均呈现先增大后减小的变化规律,且含水量达到土体的塑性含水量以后,抗剪强度降低较小。含水量对改性土、回填膨胀土和渠基土的黏聚力及内摩擦角存在着显著影响,黏聚力与含水量满足二次多项式关系;土体的内摩擦角随着土体含水量的增加呈现出非线性减小的变化规律,且渠堤改性土内摩擦角随含水量的降低幅度较渠堤膨胀土和渠基土大。

基于指标体系法的改扩建路堤高边坡施工安全风险评估

为建立改扩建路堤高边坡施工安全风险评估方法,通过对改扩建路堤高边坡施工特点分析,结合福建省的地质地貌、气候条件和自然灾害等方面资料进行分析,提出适用于福建地区路堤高边坡施工安全风险评估指标体系即一级指标2个二级指标11个,以及施工安全风险评估模型,并依托某公路改扩建项目,采用指标体系法进行改扩建路堤高边坡施工安全风险评估。结果表明:经过合理时间安排及有效的工程措施处理,路基高边坡1路段和路基高边坡2路段的施工安全风险评估值分别为35.288和39.020,施工安全风险等级均为中等风险,风险等级较低。提出的施工安全风险评估指标体系及评估模型,运用在项目改扩建路堤高边坡施工安全总体风险评估是可行的。

地震作用下绢云母片岩高路堤中土工格栅效用分析

对于采用绢云母片岩土石混合料为填料的高路堤而言,通常会出现地震作用下路堤变形严重等问题,加筋为通常做法。文中依托十巫北高速公路项目,以绢云母片岩土石混合料填筑的高路堤进行地震动力响应分析。结果表明,土工格栅具有分担部分应力,减小路堤动力加速度,以及抑制其变形的作用。对于路堤整体而言,加筋路堤的最大应力相对于未加筋路堤所承受应力较小;相比于无筋路堤,路堤加筋后加速度和速度明显减小,在路堤同一高度上土工格栅加筋土路堤的水平向峰值加速度和速度比未加筋路堤的水平向峰值加速度和速度小;土工格栅加筋对路堤整体的纵向沉降和侧向位移具有抑制效果,显著地减弱路堤在地震作用下的破坏程度。