The maintenance of structural performance integrity of the high-speed railway (HSR) track-subgrade system is crucial for ensuring the safety and stability of high-speed trains. At present, there is no uniform standard for the rapid estimation method of the evolution of track interlayer contact characteristics in the HSR track-subgrade system. Based on the structural characteristics of CRTS II slab ballastless track and the randomness of interlayer contact stiffness, the evolution model of track interlayer contact characteristics caused by differential subgrade settlement (DSS) was established, the influence of different wavelength and amplitude of DSS and existing track interlayer diseases on interlayer contact characteristics was studied, and the maintenance direction of discontinuous interlayer connection under DSS was proposed. The results show that when the DSS amplitude remains unchanged, the void beneath the slab (VBS) increases first and then decreases to 0 with the increase of settlement wavelength. Under the combined action of the randomness of track interlayer contact stiffness and DSS, the discontinuous contact area of the track still presents a symmetrical trend.VBS in the subgrade settlement area is significantly affected in the range of settlement amplitude of 5 similar to 40 mm and settlement wavelength of 5 similar to 21 m. the fastener break will not affect the interlayer contact state, while the mortar void exacerbates both mortar debonding and VBS.

To study the influence law of subgrade differential settlement on longitudinal ballastless track (LBT) irregularity considering interlayer contact stiffness randomness, this article adopts LHS to transfer interlayer contact stiffness randomness (ICSR) on the basis of previously general representation model of track deformation and interlayer contact behavior evolution induced by foundation deformation based on Castillate's second law. A mapping relationship between subgrade settlement and LBT irregularity considering ICSR is derived and solved. The results of mapping relationship, finite element model and measured data are compared, and then the influence mechanism of subgrade differential settlement on LBT geometric and stiffness irregularity is analyzed. The results show that the results of mapping relationship, finite element model and measured data are in good agreement, which verifies the correctness of the established mapping relationship considering ICSR. Considering ICSR, the influence on LBT geometric irregularity is weak, but it has significant influence on LBT stiffness irregularity. The LBT deforms with the subgrade "cosine-type" settlement under self-weight, showing a "cosine-like" deformation law. The smaller settlement wavelength will lead to void beneath slab between LBT and subgrade, while the larger settlement wavelength will inhibit LBT deformation and reduce void beneath slab. When settlement wavelength is 21-40 m, the LBT geometric irregularity amplitude is positively correlated with settlement amplitude. When settlement wavelength is gradually reduced from 21 m to 5 m, the sensitivity of LBT geometric irregularity amplitude to settlement amplitude change is reduced. When the settlement wavelength does not exceed 13 m, interlayer force increases due to the increase of settlement amplitude.

An innovative lateral deformation mapping method for track-bridge system considering the effect of pier-pile-soil was built in this study. It solves the problem that traditional mapping method cannot consider the influence of the of pile-soil and pier gravity second-order effect (P-triangle). By iteratively calculating the influence of vertical pier top force on the pier lateral deformation, the P-triangle is taken into account, and the main beam deformation formula considering the influence of pile-soil and P-triangle is formed. The main beam deformation formula is substituted into the track-bridge deformation mapping model without considering pile-soil and P-triangle developed earlier by the author. The lateral deformation mapping method of the track-bridge system considering the influence of the of pile-soil and P-triangle is established, and the finite element model is used to verify this method. Finally, the influence law of the track-bridge mapping deformation considering and ignoring the influence of the of pile-soil and P-triangle is analyzed. The results show that the rail mapping deformation determined by the proposed mapping method and finite element model are in good agreement; the maximum error does not exceed 2.5%, verifying the accuracy of the proposed mapping method in this study. Considering and ignoring the pile-soil effect has a greater impact the results of rail mapping deformation; even a tiny pier bottom rotation still has a significant impact on the mapping deformation of the track-bridge system. Hence, it is ascertained that the pile-soil effect cannot be ignored. For high-speed railway high piers, considering and ignoring the P-triangle does not significantly impact the rail mapping deformation; even when the pier is 70 m high, the impact does not exceed 0.5%. Using the proposed model, the influence of the P-triangle can be considered after only a few numbers of iterations.

A nonlinear dynamic model of a train–bridge-longitudinal track coupling system considering the dynamic contact of the bridge–track interface (BTI) is established. Based on the previously established BTI contact characterization model and train–bridge coupling joint simulation model, the proposed model is verified from both static and dynamic perspectives. Accordingly, the dynamic displacement variation law of the bridge–track structure before, during and after the train passing through the side pier settlement area, the additional stress dynamic variation law and the interlayer connection dynamic variation law are analyzed. Moreover, the amplification effect of the wheel repeated “beating effect” on the dynamic contact force of “disengagement-closure-redisengagement” of the BTI void area is also analyzed. The results show that the accuracy of the proposed model can be verified from both static and dynamic perspectives. During the train passes through the settlement area, the dynamic deformation of track is the largest. Before and after the train passes through the settlement area, the dynamic deformation of track is basically the same. During the train passes through the settlement area, the BTI completes a dynamic contact process of “disengagement-closure-redisengagement”. The static effect of the side pier settlement on the dynamic bonding force of sliding layer is much larger than the dynamic effect of the train load. The dynamic effect of the train load is much larger than the static effect of the side pier settlement on the dynamic bonding force of the CA mortar and fasteners. The side pier settlement has a dynamic amplification effect on the train wheelset. Along the mileage direction, there are interface voids and contact areas in the dynamic bonding force of sliding layer and CA mortar, while there are no voids and contact areas in the dynamic bonding force of fasteners.

The seismic performance of the CRTS II slab ballastless track lateral block (TLB) for high-speed railways (HSRs) is revealed for the first time. Nine test models of the main beam-TLB are constructed with varying quantities and diameters of interface anchorage steel bars. The model scale is 1:2, and the steel scale is 1:4. The study examines the failure mechanism, failure pattern, hysteretic curve, skeleton curve, energy dissipation capacity, ductility, stiffness degradation, and strength degradation of the TLB under low cyclic load. The influence of the diameter and quantity of interface anchorage steel bars on the seismic performance of the TLB is analyzed. The results indicate that the failure pattern of the TLB under low cyclic load can be divided into three stages: (a) the interface of the TLB and main beam initially exhibits minor cracking, which enlarges during loading and closes during unloading; (b) the interface steel bars repeatedly compress the surrounding concrete of the TLB and main beam, and the cracks continue to expand until they penetrate the entire interface, while the interface steel bars undergo shear deformation; (c) the concrete in the interface area between the TLB and main beam is crushed and spalled, and the interface steel bar experiences bending shear deformation, leading to slippage and inclination of the TLB. Increasing the quantity and diameter of interface anchorage steel bars enhances the energy dissipation capacity and ductility of the TLB, reduces the degradation of its strength and stiffness, and improves its seismic capability. However, when the diameter of interface anchorage steel bars reaches 12 mm and the quantity of steel bars reaches 8, the increase rate in energy dissipation capacity and ductility of the TLB slows down while the deterioration rate of strength and stiffness accelerates.

[Objective] During the process of EPB SC (earth pressure balanced shield construction), inevitable soil disturbances occur, causing ground deformation and subsequently impacting the surrounding built environment negatively. Therefore, conducting research on the ground deformation caused by EPB SC holds significant importance. [Method] By integrating various relevant literatures, the research is centered around the connections between each stage of the construction. The working mechanism of EPC SC is clarified, the causes of ground deformation are studied from three aspects: tunnel geometry factors, soil geological conditions, and shield tunneling parameters. The prediction methods for ground deformation caused by EPC SC are discussed, the applicability and pros and cons of each method are analyzed. Based on the causes of deformation and deformation prediction, control measures for ground deformation caused by EPB SC are listed. The shortcomings in the research of EPB SC are pointed out, and the future development direction of EPB SC is discussed. [Result & Conclusion] The causes of ground deformation induced by EPB SC are tunnel geometry factors, soil geological conditions, and shield tunneling parameters. The prediction methods for ground deformation caused by EPC SC include empirical formula method, theoretical analysis method, numerical simulation method of finite elements and finite difference, model test method, and artificial intelligence method. Based on the monitoring of ground deformation, continuously adjusting the shield parameters during construction is an effective method to control ground deformation by EPB shield.

In the current seismic analysis of high-speed railway track–bridge structures, the constitutive parameters of track lateral blocks (TLBs) are not uniform. A finite element model of the TLB’s main beam is established, which considers concrete plastic damage, interface bond between old and new concrete, and bond slip between anchorage steel bars (ASBs) and concrete. Quasi-static tests of nine TLBs with different numbers and ASB diameters at a 1:2 scale was carried out to verify the accuracy of the TLB finite element model in terms of the failure pattern, interface damage, hysteretic properties, and skeleton model. Based on the verified TLB finite element model, the influence of different TLB design parameters on its seismic performance parameters was studied. The results show that the established TLB finite element model is in good agreement with the test data in terms of failure pattern, interface damage, hysteretic properties, and skeleton model, which verifies the accuracy of the TLB finite element model. ASB number has the greatest influence on the TLB yield load, followed by ASB diameter, concrete strength, ASB strength, and ASB spacing. ASB diameter has the greatest influence on the TLB peak load, followed by ASB number, ASB strength, concrete strength, and ASB spacing. ASB diameter has the greatest influence on the TLB energy dissipation capacity, followed by ASB number, concrete strength, ASB strength, and ASB spacing. With the increase in concrete strength and ASB strength, TLB ductility decreases. When the ASB number is higher than eight or the diameter is higher than 12 mm and the corresponding interfacial steel bar ratio reaches 0.82%, the TLB ductility will decrease.

To clarify the influence range and saturation distribution after the biogas desaturation method is applied, a three-dimensional model is established with TOUGH2 software to analyze the effect of construction parameters such as grouting volume, grouting rate, grouting depth, nitrogen source concentration, and soil porosity. After that, the sensitivity of the parameters on the influence range is determined. The grouting volume and soil porosity are the most sensitive to the lateral and vertical influence range, respectively. This study provides a basis for the engineering practice of treating liquefiable subgrade by the biogas desaturation method.

在考虑压力荷载、温度荷载、压力/温度耦合荷载3种工况的前提下,分别建立了不同内径的接管部分有限元模型,分析了特种耐酸耐温耐压砖和Asplit HB胶泥在3种工况及不同接管管口内径下接管应力状态的三向应力分布规律,明确了接管管口在工作过程中各层结构的危险区域.结果表明:对于特种耐酸耐温耐压砖,管口半径越大,在压力荷载作用下,其径向、环向最大拉应力越大;在温度荷载作用下,其径向、轴向最大拉应力越大;在压力/温度耦合荷载作用下,其三向最大拉应力均越大.对于Asplit HB胶泥,管口半径越大,在压力荷载作用下,其轴向最大拉应力随着管口半径的增大而增大.在温度荷载作用下,其环向最大拉应力随着管口半径的增大而增大,轴向相反,最大拉应力随着管口半径的增大而减小.在压力/温度耦合荷载作用下,径向最大拉应力随着管口半径的增大而增大.

基于前期开发的高速铁路基础变形诱发轨道结构变形与层间接触性状演变的通用表征模型,引入余弦型路基沉降描述函数,引入用以刻画轨道-路基间接触非线性的Heaviside函数,推导余弦型路基沉降下纵连板式无砟轨道各层结构的变形方程,利用渐进性接近法求解含接触非线性的超静定方程,进而分析余弦型路基沉降对轨道各层结构变形和层间接触性状演变的影响规律.结果表明:在余弦型路基沉降区域内,轨道随路基沉降发生"跟随性"变形,当路基沉降波长一定时,轨道下沉和上拱均随路基沉降幅值的增加而增大,当沉降幅值一定时,轨道下沉随路基沉降波长的增加而增大,但上拱却减小;轨道-路基间的脱空区域及轨道的受力曲线呈左右对称,轨道整体刚度影响脱空长度和高度;当路基沉降波长为10 m时,随路基沉降幅值的增加,脱空高度和长度增长的同时,还会整体向远离沉降区方向"偏移";当路基沉降幅值为10 mm时,需要重点关注沉降波长小于20 m的不均匀沉降.

To study the evaluation standard and control limit of mortar filling layer void length, in this paper, the train sub -model was developed by MATLAB and the track-bridge sub-model considering the mortar filling layer void was established by ANSYS. The two sub-models were assembled into a train-track-bridge coupling dynamic model through the wheel-rail contact relationship, and the validity was corroborated by the coupling dynamic model with the literature model. Considering the randomness of fastening stiffness, mortar elastic modulus, length of mortar filling layer void, and pier settlement, the test points were designed by the Box-Behnken method based on Design-Expert software. The coupled dynamic model was calculated, and the support vector regression (SVR) nonlinear mapping model of the wheel-rail system was established. The learning, prediction, and verification were carried out. Finally, the reliable probability of the amplification coefficient distribution of the response index of the train and structure in different ranges was obtained based on the SVR nonlinear mapping model and Latin hypercube sampling method. The limit of the length of the mortar filling layer void was, thus, obtained. The results show that the SVR nonlinear mapping model developed in this paper has a high fitting accuracy of 0.993, and the computational efficiency is significantly improved by 99.86%. It can be used to calculate the dynamic response of the wheel-rail system. The length of the mortar filling layer void significantly affects the wheel-rail vertical force, wheel weight load reduction ratio, rail vertical displacement, and track plate vertical displacement. The dynamic response of the track structure has a more significant effect on the limit value of the length of the mortar filling layer void than the dynamic response of the vehicle, and the rail vertical displacement is the most obvious. At 250 km/h - 350 km/h train running speed, the limit values of grade I, II, and III of the lengths of the mortar filling layer void are 3.932 m, 4.337 m, and 4.766 m, respectively. The results can provide some reference for the long-term service performance reliability of the ballastless track-bridge system of HRS.

研究目的:以某主跨48 m+80 m+48 m三跨连续梁桥、两侧各2跨简支引桥及200 m长路基的高铁线路为研究对象,采用CRH3、CRH2C和CRH380A高速动车组,以德国低干扰谱和中国无砟轨道谱为初始轨道不平顺,以映射关系求得的连续梁边墩沉降致轨道变形为附加轨道不平顺,分别评估不同车型高铁列车在不同轨道不平顺谱激励下的走行性.研究结论:(1)建立的车-轨-连续梁桥动力学模型与文献模型计算结果吻合良好;(2)中国无砟轨道谱在舒适性、平稳性及安全性上均明显优于德国低干扰谱;(3)初始轨道不平顺激励下,对安全性影响强弱依次为CRH380A＞CRH3＞CRH2C,对舒适性影响强弱依次为CRH3＞CRH380A＞CRH2C,对平稳性影响强弱依次为CRH3＞CRH380A＞CRH2C;(4)附加轨道不平顺激励下,对安全性和舒适性影响强弱同初始轨道不平顺,而平稳性随边墩沉降值变化较大,德国低干扰谱激励下,对平稳性影响强弱依次为CRH3＞CRH380A＞CRH2C,中国无砟轨道谱激励下,对平稳性影响强弱依次为CRH2C＞CRH3＞CRH380A;(5)本研究结果可为高铁线路中主跨为连续梁桥的设计与验算提供一定参考.

Based on the shield tunnel construction of the left line of Guowei road station-Qingshan lake west station of Nanchang metro line 3, the study focuses on the adverse effects of tunnel segment convergence and settlement deformation of vault and arch bottom on shield construction in the process of shield tunnel construction in water-rich complex stratum. The time-space curves of segment convergence and settlement value on typical monitoring sections are drawn, their variation laws are analyzed, and the deformation values of monitoring data are analyzed and tested. Based on the analysis results, the qualitative and quantitative evaluation of the overall or local deformation state of each monitoring object of tunnel segment is carried out. The results show that the cumulative deformation of each typical monitoring section is lower than the warning value, and the tunnel segment has a systematic offset in the horizontal and vertical directions of the clearance.

祁连山区位于青藏高原东北边缘,是亚洲水塔重要的组成部分,多年冻土的变化对生态系统和水资源平衡有着重要影响.基于青藏高原第二次综合科学考察、道路勘察钻孔点以及前人所获得的多年冻土下界资料,回归得出祁连山区多年冻土下界统计模型,借助ArcGIS平台在DEM数据的支持下,模拟出祁连山区多年冻土空间分布图.结果表明:祁连山区多年冻土分布的下界具有良好的地带性规律,表现为随经纬度增加而降低的规律;祁连山区多年冻土在空间分布上呈现出以哈拉湖为中心向四周扩散的分布格局;祁连山区总面积约为16.90×104 km2,其中多年冻土面积约为8.03×104 km2,占总面积约47.51％.多年冻土区与季节冻土区之间存在着有不连续多年冻土分布的过渡区,过渡区面积约1.43×104 km2,占总面积约8.46％.

By applying the method of unidirectional freezing, a series of laboratory tests were carried out to study the anti-frost jacking ability of belled piles in seasonal frozen soil regions. The tests were conducted on piles with different bell angles (non-bell, 45º, 60º and 70º), different embedded depths (240 mm, 290 mm and 340 mm), and different bell diameters (74 mm, 98 mm and 114 mm). Based on the test and calculated results, the ultimate freezing depths of the three test groups were 19.51 cm, 14.36 cm and 14.80 cm, respectively. The ultimate frost jacking displacements of belled piles with different bell angles were almost the same, which were merely 28.3% of the straight pile. The ultimate frost jacking displacements of belled piles didn’t decrease in proportion with the increase of embedded depth, but it decreased in proportion with the increase of enlarged base diameter. With the increase of freezing depth, the frost jacking amount amplitude of the piles increased first and then decreased, and it was negatively correlated with the soil freezing rate. The frost jacking rate of straight pile increased first and then decreased rapidly with the increase of freezing depth, while the frost jacking rate of belled pile increased first and then decreased steadily with the increase of freezing depth. The frost heave of soil had a funnel shape under the constraint of pile. Further, the constraint effect of belled pile was stronger than that of straight pile, which indirectly indicated that the anti-frost jacking ability of belled pile was better than that of straight pile. Considering the freezing rate of soil and frost jacking amount of pile in the freezing process, the concept of anti-frost jacking factor of pile was proposed as the criterion of anti-frost jacking ability of pile, and anti-frost jacking effects of belled piles were also analyzed under different influencing factors. The analysis showed that the anti-frost jacking ability of pile was less affected by bell angle, but it could be improved by increasing the embedded depth and diameter of enlarged base. Comprehensive comparison showed that the diameter of enlarged base was the most important factor affecting the anti-frost jacking ability of pile, followed by the buried depth of the pile, and the smallest influence was the bell angle. The test results and analyses can provide references for designing and theoretical calculation of belled piles in seasonal frozen soil regions.

为研究冻胀过程中管-土之间的相互作用规律及受力特征,以不锈钢管及冻胀敏感性粉质黏土为材料,在没有外界水源补充的小型环境模型试验机中进行试验.首先,黏贴电阻应变片于管道上,并将管道及其支架放置于敞口保温箱内;其次,填装土样并同步在每个测点布置温度、水分和土压力传感器;最后,在试验过程中实时监测土体的温度、含水率、土压力、冻胀量及管道的变形和应力等变量,主要分析与讨论降温阶段即持续70h的冻胀阶段所采集数据.研究结果表明:冻胀过程中管道抑制土体冻胀的实质是抑制土体的水分迁移;管土之间相互协调发展且始终保持着动态平衡,冻胀导致管道发生变形的同时管道又约束着土体的冻胀,冻胀受约束而产生土压力;管道变形以及与管道的距离决定管道对土体冻胀的约束程度;管道变形越小,约束率越大,土压力越大,水分迁移量越小,冻胀越小;而同一时刻管轴线两侧土体的冻胀明显比管底土体的大,且距离管道越远的位置,约束率越小,土压力越小,水分迁移量越大,冻胀越大;土压力随着时间而增大,与约束率呈指数增大的关系,但与冻胀呈指数衰减的关系;冻胀引起管道产生轴向及环向应力,轴向最不利应力分布位置为管中4/8处;环向应力的存在说明管道发生截面变形,在较大的冻胀力或外荷载作用在管道上时,环向应力的影响不可忽视.

Previous studies have shown that an accurate prediction of frost heaves largely depends on the pore water pressure and hydraulic conductivity of frozen fringes, which are difficult to determine. The segregation potential model can avoid this problem; however, the conventional segregation potential is considered to be approximately unchanged at a steady state and only valid in an open system without dehydration in the unfrozen zone. Based on Darcy’s law and the conventional segregation potential, the segregation potential was expressed as a function of the pore water pressure at the base of the ice lens, the pore water pressure at the freezing front, the freezing temperature, the segregation freezing temperature and the hydraulic conductivity of the frozen fringe. This expression indicates that the segregation potential under quasi-steady-state conditions is not a constant in a closed system, since the pore water pressure at the freezing front varies with the freezing time owing to the dehydration of the unfrozen zone, and that when the pore water pressure at the freezing front is equal to that at the base of the ice lens, the water migration and frost heave will be terminated. To analyze the possibility of applying the segregation potential model in a closed system, a series of one-sided frost heave tests under external pressure in a closed system were carried out in a laboratory, and the existing frost heaving test data from the literature were also analyzed. The results indicate that the calculated frost heave was close to the tested data, which shows the applicability of the model in a closed system. In addition, the results show the rationality of calculating the segregation potential from the frost heaving test by comparing the potential with that calculated from the numerical simulation results. This study attempted to extend the segregation potential model to freezing soil in a closed system and is significant to the study of frost heaves.

在深季节冻土区,正冻土和桩相互作用时可能会导致桩基的拔断或整体冻拔破坏.在桩周土冻胀过程中,等截面直桩主要通过桩和未冻区融土间的摩阻力达到锚固效果.而对于端部直径大于桩身直径的扩底桩来说,当桩基有整体上拔的趋势时,扩大头会受到上覆土层的阻力而起到锚固/抗冻拔作用.通过回顾国内外研究文献,介绍了扩底抗拔桩现有的工程背景及应用情况,并对季节冻土区桩基的受力性能进行了总结和分析,主要内容包括:土体冻胀和桩基的相互作用研究,切向冻胀力试验研究和理论研究,切向冻胀力作用下扩底桩基冻胀反力试验研究及理论研究,切向冻胀力作用下未冻区桩-融土间摩阻力的研究概况等.最后,结合现有的研究内容,对季节冻土区扩底桩的应用及研究提出进一步的展望.

以考虑两侧引桥与路基的高速铁路CRTSⅡ型板式无砟轨道-连续梁桥系统(HBBSS)为例,研究轨道系统中各关键构件的地震响应规律及参数影响分析,基于有限元方法建立HBBSS地震分析模型,分析HBBSS中各关键构件的地震响应规律以及刚度变化对HBBSS地震响应的影响分析.结果表明:HBBSS中各关键构件的地震损伤顺序依次为滑动层、CA砂浆和剪切钢筋;剪力齿槽和扣件在设计标准规定的设防烈度下难以损伤;CA砂浆、滑动层及剪切钢筋是HBBSS地震响应的重要影响因素,在抗震设计中应加以关注.

土体冻胀产生的切向冻胀力是制约寒区基础工程建设和使用年限的主要原因,同时也是基础设计中的一个重要参数,深入研究切向冻胀力问题意义重大.通过回顾国内外相关文献,对切向冻胀力目前的研究现状进行了总结:从切向冻胀力产生的条件和过程角度出发,详细描述了切向冻胀力产生发展的机理;阐述了影响切向冻胀力的因素和切向冻胀力的分布规律;从试验、理论两方面入手,简要总结了切向冻胀力的测试方法和理论计算方法;简述了目前确定切向冻胀力取值的方法.最后,对切向冻胀力未来的研究方向提出了展望.