排水管堵塞引起的高铁隧道结构变形与渗流场特征模拟试验研究

基于3D打印技术构建了高铁隧道结构及排水系统设施精细模型,提出了切实可行的隧道堵管模拟方法及模拟装置,依托典型病害案例开展了堵管病害相似模型模拟试验,探讨了在不同堵管条件、不同地层水头下隧道渗流场(隧道排水量、结构外水压力)及结构位移量的变化规律特征。研究结果表明:随堵塞程度加深,隧道排水量呈现先慢后快型下降趋势,具体为排水管堵塞率为50%前隧道排水量下降幅度较小,而堵塞率达50%后隧道排水量骤减直至不排水;底部结构隆起位移存在"隧底>内轨>外轨"的量值关系,且随堵塞程度加深隆起位移呈现先慢后快型增长趋势;受排水减少影响,堵管后结构外水压力逐步由"隧底最大,拱顶、拱腰次之,墙脚最小"的扇贝型分布转为"静水压"型分布;至全堵条件下地层水头40 m时试验位移结果与现场病害特征吻合良好,验证了上述模拟方法的可行性与有效性。研究成果以期为富水隧道堵管防治及类似病害评价提供借鉴与指导作用。     

某边坡挡墙特殊排水设计方法研究

某边坡挡墙因地下水具强腐蚀性,影响安全性和耐久性,为了解决这一突出矛盾,边坡挡墙采取了特殊排水设计,该设计方法避免了腐蚀性地下水对挡墙的大面积腐蚀,提高了挡墙的安全性和耐久性,为类似的工程设计提供参考。     

Chemical injection application at tunnel service shaft to prevent ground settlement induced by groundwater drainage: A case study

Chemical injections are used in a variety of applications in civil and mining engineering, including ground stabilization, support anchoring, strata sealing, reduction and diversion of groundwater flow and water ingress, and creation of a load-bearing ring during tunneling. Historically, injection application without pressure was first employed by the Romans. Polyurethane injections have been used in coal mines to stabilize roofs and to reduce problems regarding water ingress in shafts and tunnels. This paper focuses on chemical injection, which was employed to prevent ground settlement induced by groundwater drainage from the shaft. As a result of the drainage of 4.5 l/s groundwater from the Shaft 4, which was sunk for service at Guzelyali station of Izmir Metro Project, the groundwater level dropped 4 m from the original level, and ground settlement reached 98 mm, while the inner tunnel vertical convergence was 23 mm. This can be explained with the closure of pore volumes in the overburden. Ground settlement was stopped and groundwater level approached its original level after chemical injection.     

Laboratory evaluation of a new device for water drainage in roadside slope along railway systems

The majority of the existing railway systems in China, from roadside slopes to retaining walls, suffered from poor drainage induced failures. Recently, a new drainage device was proposed to tackle these problems. Preliminary field implementations indicated that the new drainage device could effectively remove groundwater from the surrounding soil without any clogging effect. However, at present, most existing designs are purely based upon the engineers' personal experience and judgement; there is no well-established design method to take full advantage of the device.In this study, a series of laboratory modeling tests were conducted to investigate flow rates, and the optimum installation angle of the drainage device. After that, the long-term performance of the drainage device and conventional perforated PVC pipe under multiple wetting-drying cycles was also evaluated and compared. The results indicate that during the constant head tests, the flow rates in the new drainage device initially increased with an increase in the installation angles of the drainage device from 0° to 15°, and then decreased from 15° to 60°. An inclination angle from 5° to 15° is recommended for this new drainage device when installed in the exiting railway cut slope. The clogging effect was not a primary concern for the applications of this new device. The proposed drainage device provides an alternative way to tackle the poor drainage problem in the exiting railway cut slopes and retaining walls.     

Internal explosive loading of steel pipes

A programme of numerical, analytical and experimental studies is being carried out at the University of Liverpool on seamless steel pipes 9.5 mm thick with an outer diameter of 324 mm which have been subjected to internal explosive loading. The objective of the study, which is sponsored by AWE plc, Aldermaston, is to determine the failure mechanism of such a pipe under a very high rate of loading. The loading imparted to a vessel wall, arising from the detonation of a high explosive is sensitive to the charge shape. Numerical simulations have shown that for the same charge weight, a cylinder-shaped charge, of equal diameter and length, produces more deformation than the equivalent sphere. A Johnson–Cook strength model in the numerical simulation is in good agreement with test data.     

CFD-DEM modeling of geotextile clogging in tunnel drainage systems

In this study, a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) method we used to investigate the hydraulic deterioration of a geotextile due to clogging in tunnel drainage systems. Initially, a framework was developed to generate and test a numerical representation of a typical non-woven geotextile. Following model validation, we carried out parametric analysis to examine the effect of fine content, crack angle, and groundwater inflow. The results showed a general trend of pressure increase associated with increasing both the crack angle and fine content. This increase was found to decay at larger crack angles and high content of fines. Interestingly, increasing groundwater inflow was found to had minimal effect on the final deposition of the clogging particles. Finally, an approximate semi-analytical model was developed to describe the pressure increase due to clogging. The model was able to provide a good match with the data obtained from the numerical analysis.     

注浆作用对微型钢管桩抗压承载性能影响的试验研究

为了研究注浆作用对钢管桩承载性能的影响,本文开展了160 mm、200 mm两种桩径、5 m和8 m两种入土深度、注浆与不注浆两种条件下共18个试验桩的现场抗压静载荷试验,分析了注浆作用对钢管桩荷载位移曲线、极限承载力及破坏模式的影响。结果表明:注浆作用使钢管桩荷载位移曲线上的中间曲线段更加明显,塑性变形范围增加;注浆作用整体提高桩基承载力30%以上,管径最细、埋深最浅的I#桩提升效果最明显;注浆过程中浆液在桩周土中产生劈裂、渗扩、填充、胶结、压密等一系列物理化学作用,最终在桩端形成“水泥土加固体”,在桩侧形成水泥土护壁,改善了桩端土、桩周土的物理力学性能,从而提高了桩基承载力。     

云南某在建隧道排水管结晶堵塞病害初步探析

云南某在建隧道地处中缅边境,岩性多为泥岩和砂岩,地下水质富含重碳酸盐。通过对该隧道地下水、初支表面渗流水点、排水管流出溶液的长期监测以及现场试验,对该隧道结晶堵塞机理和处治方式进行了初步探析,旨在为类似隧道提供一定借鉴和参考,得到的主要结论有：地下水质是影响结晶体生成非常重要的因素,特别对于重碳酸盐型地下水质,其隧道排水管中更易产生大量结晶体;排水管流出溶液流量大小关联渗流离子浓度和晶体堆聚能力,是影响排水管中堵塞生成的重要因素;减少地下水与初支喷射混凝土的接触,避免地下水与水泥水化产物发生化学反应,是减少结晶体生成量一种有效的方式;喷射混凝土中掺加适量粉煤灰,对降低结晶体的生成量有一定的效果。     

Evaluation of advanced drainage treatment for old tunnel drainage system in Korea

This study was dealt with clogging problems of the drain aperture in old tunnels. The precipitates in the drainage were mainly generated by degradation of the tunnel concrete lining. The degradation was made by the chemical reaction between the concrete material and groundwater. If the degree of precipitation is high in the tunnel drainage, the groundwater cannot flow easily in it. Consequently, the groundwater level will go up, and this can lead to the highest water pressure which affects to the structural risk of tunnel. The degraded drainage causes to generate not only the structural stability of tunnel, but also the additional maintenance problem. Up to this time the technical study of preventing the scale for just tunnel drain aperture was rare. However, there are some preventive technologies about the scale for the industrial facilities such as oil pipe lines etc. There are two most popular technologies. One is Quantum Stick using Brown’s principle of quantum mechanics and the other one is Magnetizing device to inhibit the scale formation by changing the form of calcium carbonate particles. In this study, in order to improve the clogging problem in the tunnel drain aperture the elementary technologies were introduced. In addition, the laboratory tests were conducted to evaluate their applicability using the results from SEM and XRD analysis on the sediment generated during the test. As a result, Quantum Stick showed the reasonable effect of scale removing under the condition of more than velocity limit.     

Modelling of hydraulic deterioration of geotextile filter in tunnel drainage system

The discharge capacity of a tunnel drainage system generally decreases with time because of the hydraulic deterioration of the geotextile filter. Hydraulic deterioration restricts groundwater flow into a tunnel and increases water pressure resulting in detrimental effects on the tunnel lining. Hydraulic deterioration of tunnel drainage system is unique in terms of clogging materials, deterioration mechanism, and flow conditions. Current studies and models investigating the clogging mechanism and hydraulic deterioration are not directly applicable to the geotextile filter of the tunnel drainage system. In this study, a theoretical model of the hydraulic deterioration of tunnel geotextile filter has been proposed considering the mechanical and hydraulic behavior of blinding, clogging and squeezing. A parametric study was carried out to evaluate the performance of the model. An experimental study has been conducted to investigate the clogging behavior of the tunnel drainage system and validate the theoretical model. Several types of clogging materials were selected: cement-leaching calcium oxide, calcium carbonate, iron oxide, and bentonite. Agglutinated clogging was mainly observed during the short-term testing. The findings suggest that the in-plane permeability of the geotextile filter decreased by approximately 90%. The proposed model corroborated the experimental results.     

大型屋面虹吸雨水排水管道安装

介绍了我国澳门威尼斯入度假村裙楼屋面雨水排水系统,对虹吸雨水系统的管道安装及调试运行进行了分析总结,指出虹吸雨水排水系统应用在大型屋面和造型复杂的屋面比重力流排水系统中具有许多优越性,能够更好地排除屋面雨水。     

管网渗流系统对边坡剩余下滑推力影响的物理模拟研究

为了研究管网渗流系统对土体渗透性能和地下水位以及边坡剩余下滑推力的影响,进行管网渗流系统的物理模拟试验。试验结果表明,管网渗流系统可提高坡体的渗透性,降低地下水位,从而使边坡剩余下滑推力明显减小,从而提高边坡的稳定性。指出在含碎石黏性土滑坡的防治中,应将地下水排水措施作为主要防治措施。     

浅谈HDPE管屋面虹吸排水系统施工技术要求

从HDPE管材切割、管材的热熔准则、热熔步骤及安装步骤介绍HDPE管屋面虹吸排水施工技术要求，以完善HDPE管屋面虹吸排水施工工艺，推广HDPE管屋面虹吸排水在工程中的应用。     

Experimental investigation on the invert stability of operating railway tunnels with different drainage systems using 3D printing technology

In recent years, the invert anomalies of operating railway tunnels in water-rich areas occur frequently, which greatly affect the transportation capacity of the railway lines. Tunnel drainage system is a crucial factor to ensure the invert stability by regulating the external water pressure (EWP). By means of a three-dimensional (3D) printing model, this paper experimentally investigates the deformation behavior of the invert for the tunnels with the traditional drainage system (TDS) widely used in China and its optimized drainage system (ODS) with bottom drainage function. Six test groups with a total of 110 test conditions were designed to consider the design factors and environmental factors in engineering practice, including layout of the drainage system, blockage of the drainage system and groundwater level fluctuation. It was found that there are significant differences in the water discharge, EWP and invert stability for the tunnels with the two drainage systems. Even with a dense arrangement of the external blind tubes, TDS was still difficult to eliminate the excessive EWP below the invert, which is the main cause for the invert instability. Blockage of drainage system further increased the invert uplift and aggravated the track irregularity, especially when the blockage degree is more than 50%. However, ODS can prevent these invert anomalies by reasonably controlling the EWP at tunnel bottom. Even when the groundwater level reached 60 m and the blind tubes were fully blocked, the invert stability can still be maintained and the railway track experienced a settlement of only 1.8 mm. Meanwhile, the on-site monitoring under several rainstorms further showed that the average EWP of the invert was controlled within 84 kPa, while the maximum settlement of the track slab was only 0.92 mm, which also was in good agreement with the results of model test.     

Introduction of the leak-before-break (LBB) concept for cast iron water pipes on the basis of laboratory experiments

Failure of cast iron water mains in Australia is a common occurrence. Water utilities are seeking solutions to optimise the renewal and rehabilitation of ageing cast iron critical water mains (diameter ≥ 300 mm). Failure pressures of three large-diameter cast iron pipe specimens (600 mm in diameter) were tested. A large corrosion patch was machined onto each pipe section to initiate pipe failure. A large corrosion patch and significant reduction (>90%) of pipe wall thickness were needed to fail the tested pipe specimens. All three pipes under test exhibited leaking before bursting, indicating that the concept of leak-before-break (LBB) could be used for pipe failure prevention. In addition, LBB provides valuable information that could be added to the pipe asset database to make better management decisions on repair or replacement along with all other asset information. The study also found that small corrosion patches (<50 mm) with low remaining wall thickness may cause pipe leaks, but are less likely to cause major pipe bursts.     

On the critical particle size of soil with clogging potential in shield tunneling

Shield tunneling is easily obstructed by clogging in clayey strata with small soil particles. However, soil clogging rarely occurs in strata with coarse-grained soils. Theoretically, a critical particle size of soils should exist, below which there is a high risk of soil clogging in shield tunneling. To determine the critical particle size, a series of laboratory tests was carried out with a large-scale rotary shear apparatus to measure the tangential adhesion strength of soils with different particle sizes and water contents. It was found that the tangential adhesion strength at the soil–steel interface gradually increased linearly with applied normal pressure. When the particle size of the soil specimen was less than 0.15 mm, the interfacial adhesion force first increased and then decreased as the water content gradually increased; otherwise, the soil specimens did not manifest any interfacial adhesion force. The amount of soil mass adhering to the steel disc was positively correlated with the interfacial adhesion force, thus the interfacial adhesion force was adopted to characterize the soil clogging risk in shield tunneling. The critical particle size of soils causing clogging was determined to be 0.15 mm. Finally, the generation mechanism of interfacial adhesion force was explored for soils with different particle sizes to explain the critical particle size of soil with clogging risk in shield tunneling.     

长安大学地质科技大厦南侧基坑倒塌事故分析与处理

某基坑南侧支护工程原采用土钉墙支护,在土钉墙施工过程中,因遇连续降雨,靠近基坑南侧边坡处的地下排水管道由于排水不畅而导致雨水倒流进入土钉墙内;加上不规范的施工方法,致使正在施工中的土钉墙及边坡出现大面积的坍塌。针对这一工程事故进行详细地分析计算,在确定事故原因之后,对原设计方案作出调整;重新施工时,改用锚杆与砖墙组合方案。并对黄土地区土钉墙的施工提出了几点建议:注意排水、规范施工、动态设计以及信息化施工。     

Cracking mechanism of secondary lining for a shallow and asymmetrically-loaded tunnel in loose deposits

Tunnels constructed in loose deposits with low strength and complex composition are usually subjected to asymmetrical stresses at the entrance and exit. The secondary tunnel lining is prone to excessive deformation, cracking, or even collapse, seriously affecting the safety of tunnel construction and operation. In this paper, a large shallow highway tunnel in loose deposits is used as an example to study the cracking mechanism of secondary lining. Triaxial consolidated-drained shear tests are carried out on large remolded specimens to obtain the mechanical parameters of the surrounding soil. Three-dimensional numerical modeling is conducted based on the field monitoring data to simulate the process of tunnel construction and to analyze the mechanical mechanism of cracking in the secondary lining. It is shown that even with the 30 m advance pipe roof at the tunnel entrance, the apparent difference in stiffness between the retaining wall and the surrounding soil results in an obvious stress concentration at the spring of the secondary lining near the end of the retaining wall, due to the effect of highly asymmetrical stresses. In addition, loose deposits are very sensitive to construction disturbances. Large horizontal deformation towards the lower topography occurs during tunnel construction. With increasing overburden depth, the stress concentration at the spring level and the horizontal deformation in the secondary lining increases, which are the main reasons for cracking in the secondary lining. These findings can be useful for tunnel design and construction in the similar type of loose deposits.     

地下水位对某地下综合管廊稳定性影响研究

基于Midas软件,采用有限元分析方法开展数值模拟,分析了不同标高地下水位条件下,地下综合管廊的变形、内力和某一截面的安全系数。并将不同条件下的各项力学指标进行对比分析发现,随着地下水位不断上升,地下综合管廊主体结构最大弯矩由66.4 kN·m变为106.4 kN·m,最大剪力由134.7 kN变为224.3 kN,出现位置也从中间转变为腋角,同时最大水平位移大幅增加,由0.22 mm变为1.71 mm。某一截面安全系数由8.12降低到7.1,地下综合管廊主体结构虽仍处于安全的稳定状态,但稳定性不断下降。本文综合分析了地下水位升高对地下综合管廊稳定性的影响,为实际工程中不同地下水位条件下地下综合管廊保持稳定提供参考。     

Short- and long-term behavior of EPS geofoam in reduction of lateral earth pressure on rigid retaining wall subjected to surcharge loading

Retaining walls are subjected to dead loads from backfill and adjacent structures, live loads and other loads from the vicinity of the structure. Retaining walls need to withstand earth pressure generated from above mentioned loads satisfactorily throughout their service life. Lateral earth thrust on retaining walls can be minimized by placing a compressible inclusion, such as, EPS geofoam, between the backfill and retaining wall. The present study is aimed at understanding both short- and long-term influence of EPS geofoam on surcharge induced lateral earth pressures on retaining walls through 1-g model studies. Four densities of geofoam in the range of 10–25 kg/m³ and three thicknesses of geofoam in the range of 25–75 mm were used in the present study. Lateral earth pressure at several locations along the height of the wall were monitored using earth pressure cells. Geofoam compression and backfill settlements under the surcharge load were also quantified using image analysis. From the series of model tests, it was observed that with the use of geofoam, lateral earth pressure on retaining wall was reduced under both short- and long-term loading conditions. However, higher reduction was observed under long-term loading.