探地雷达在路基灌浆效果检测中的应用

探地雷达自出现以来,在工程领域得到了极其广泛的运用,获得了较好的应用效果。文章结合工程实例,介绍探地雷达在路基灌浆检测中的应用情况,实践证明,探地雷达用以检测路基的注浆质量,获得了较好的检测效果。     

注浆加固技术在宁夏同沿高速公路中的应用

路基不均匀沉降严重影响公路工程质量,采用注浆技术对路基进行加固能有效处理此类问题.文章结合宁夏境内同(心)-沿(川子)高速公路工程实践,对注浆加固技术的机理、施工工艺和质量检验等进行介绍.     

百罗高速公路路基注浆加固工程实例分析

文章介绍了路基注浆的原理和流程,分析了传统路基注浆施工中存在的问题,从计量方式和注浆方法两个方面提出了路基注浆施工的改进方法,并结合百罗高速公路工程实例,评述了路基注浆改进方法的应用效果。     

探地雷达在万丈盐桥地质勘察中的应用

万丈盐桥路段的岩盐沉积层是在气转向干燥时盐湖水分蒸发条件下盐分结晶而形成的独特地层.近20年来,由于气候条件的变异以及盐湖资源的大规模开发,交通量大增,盐湖地区钾肥生盐田建设、配比卤给排水工程等因素,湖区范围内环境条件发生了很大变化,致使岩盐公路路基发生溶蚀病害,直接影响了盐湖公路的正常使用和行车通过能力.在结晶岩盐区较多路段存在的盐壳下部空隙结晶岩盐层更可能是受到上部低矿化度水分的侵蚀而引起的结晶盐溶解形成的.在本次勘察中,探地雷达信号未能显示出大型空穴的存在迹象.因此,采用灌浆填充空穴的方案未必对这种具有潜在危险的路段有效.     

台风引起的滨德高速公路路基边坡水毁抢修、加固措施

受台风"达维"影响,刚建成通车的滨德高速公路路基边坡水毁严重,在现场调查路基边坡水毁的基础上,对路基边坡水毁进行了成因分析,归纳提出公路路基边坡水毁的破坏形式,并提出相应的灾后恢复加固措施。     

袖阀管注浆工艺在深圳地铁地层加固中的应用

文章介绍了处于特殊地质条件下地铁施工地层加固的一种新型注浆方法--袖阀管注浆法的方案设计和施工工艺,总结了袖阀管注浆的方法、在施工过程中所采取的措施和取得的经验,简述了新技术新工艺的试验应用情况.通过注浆效果,表明该项新技术、新工艺的可行性,保证了地铁顺利施工的安全和质量.     

围岩加固注浆技术在软弱富水大断层施工中的应用与研究

齐岳山隧道F11断层纵向长235 m,断层处主要为高压富水软弱围岩.施工中通过改变原有的注浆施工理念,将原帷幕注浆“柱加固模式”,优化为“桶状加固模式”;通过不断的技术优化,在保证注浆施工质量和开挖施工安全的前提下,将原全断面帷幕注浆192个孔优化为102个,将注浆工期从288天提前为133天.实践证明,围岩加固技术在投资、工期等方面较全断面帷幕注浆法具有比较明显的优势.     

基于劈裂注浆在机场场道扩建工程中的应用

在社会经济快速发展的今天,民航事业的快速发展为我国居民的出行和货物运输提供了巨大便利.过去我国的飞机少,机场建设是薄弱环节,相关的基础设施建设也不足.这些都影响了民航事业的发展.随着我国经济实力的不断崛起,我们得以拥有更多的资金和相关物资投入到机场的建设中.当前,民航事业发展越来越快.但过去已经建设完成的机场显然无法满足实际需求,这就需要进行扩建,建设技术方面也需要进一步拓展.从现有的技术使用情况来看,分层劈裂注浆是较为合适的一种,其能够有效地加固淤泥层地基,并且在短时间快速地完成施工要求,解决施工机械高度受限等等的问题,因而在今天的机场施工扩建工程中得到广泛应用.对此,笔者将在本文中针对该项技术的使用展开探讨.     

地质雷达在路基压实效果无损监测中的应用研究

探地雷达是近年在我国开始应用于高速公路检测的一项新技术,文章结合高速公路施工实践,介绍利用探地雷达在路基压实效果无损监测中的应用情况,通过对探地雷达现场应用可行性分析研究,得出利用探地雷达检测路基压实度的方法。     

Application of wavelet technique to freeway incident detection

This paper presents an application of the wavelet technique to freeway incident detection because wavelet techniques have demonstrated superior performance in detecting changes in signals in electrical engineering. Unlike the existing wavelet incident detection algorithm, where the wavelet technique is utilized to denoise data before the data is input into an algorithm, this paper presents a different approach in the application of the wavelet technique to incident detection. In this approach, the features that are extracted from traffic measurements by using wavelet transformation are directly utilized in detecting changes in traffic flow. It is shown in the paper that the extracted features from traffic measurements in incident conditions are significantly different from those in normal conditions. This characteristic of the wavelet technique was used in developing the wavelet incident detection algorithm in this study. The algorithm was evaluated in comparison with the multi-layer feed-forward neural network, probabilistic neural network, radial basis function neural network, California and low-pass filtering algorithms. The test results indicate that the wavelet incident detection algorithm performs better than other algorithms, demonstrating its potential for practical application.     

重力式锚杆挡土墙在高速公路中的运用

对于高度不超过5 m的路基挡土墙,通常选择施工简便、经济的重力式挡土墙。但该型式挡土墙受墙高限制,不适合处理较高路基边坡。通过借鉴锚杆挡土墙,将重力式挡土墙断面进行优化、组合,在充分利用当地施工条件的同时,也解决了高路基重力式挡土墙抗倾覆、抗滑移不满足设计规范要求的难题,拓展了其应用范围。     

水平袖阀管深孔注浆在广州地铁的应用

在城市地铁施工中,由于隧道埋深相对较浅,且经常要穿越工程地质复杂、水文地质极差、围岩级别较低的地段,若采用矿山法施工,通常要采用大管棚、超前小导管、水平冻结……等辅助措施.文章结合广州地铁二号线纪-越区间隧道实际施工情况,介绍了另外一种辅助工法--水平袖阀管深孔注浆,并将它与同时采用的超前小导管注浆进行多方面比较,得出了水平袖阀管深孔注浆优于超前小导管注浆并具有广泛适用性的结论.     

Average time gaps in congested freeway flow

Characteristics of time gaps (that is, the time separation between the rear of the lead vehicle and the front of the following vehicle) in congested freeway flow provide an important link between microscopic and macroscopic traffic flow. Although individual time gaps are a microscopic phenomenon, average time gaps can easily be determined from commonly collected macroscopic traffic flow data. Data from San Diego freeways and the Queen Elizabeth Way in Ontario, Canada are analyzed to show that average time gaps in congested flow are essentially constant with respect to speed; that they vary considerably between lanes at a single location and, for the same lane, from site to site; that they display considerable scatter; and that at some sites there is a distinct increase in average time gaps in the median lane in the transition to congested flow but at others there is no change or a slight reduction. The variability of average time gaps is not easily explained, although differences in driver populations may partly explain differences among different sites. Hysteresis due to acceleration and deceleration does not appear to be an explanation for the high degree of scatter in average time gaps, since no positive correlation was found between speed changes and average time gaps.     

Safety aspects of freeway weaving sections

One source of vehicle conflict is the freeway weaving section, where a merge and diverge in close proximity require vehicles either entering or exiting the freeway to execute one or more lane changes. Using accident data for a portion of Southern California, we examined accidents that occurred on three types of weaving sections defined in traffic engineering: Type A, where every merging or diverging vehicle must execute one lane change, Type B, where either merging or diverging can be done without changing lanes, and Type C, where one maneuver requires at least two lane changes. We found no difference among these three types in terms of overall accident rates for 55 weaving sections over one year (1998). However, there were significant differences in terms of the types of accidents that occur within these types in terms of severity, and location of the primary collision, the factors causing the accident, and the time period in which the accident is most likely to occur. These differences in aspects of safety lead to implications for traffic engineering improvements.     

Detection-delay-based freeway incident detection algorithms

Even though incident detection algorithms are designed and implemented for quickly detecting incidents, the criterion of mean detection delay has hardly been well defined and utilized in developing and evaluating incident detection algorithms. In addition, most incident detection algorithms do not have an optimal property in terms of detection delay with respect to false alarm rate. In the study presented in this paper, the incident detection problem was formulated as an optimization problem. To implement the algorithm, called the CUSUM algorithm that was derived from the optimization formulation of the incident detection problem, a simplified procedure was developed. Based on this procedure, three varieties of the CUSUM algorithm were developed and tested based on real incident data against a newly defined criterion for mean detection delay. Selected incident detection algorithms were also compared with the CUSUM algorithms. The comparison demonstrates the superiority of the CUSUM algorithms against other selected algorithms in reducing detection delay while maintaining an acceptable detection rate.     

Empirical analysis of freeway flow-density relationships

Many researchers have reported on the occurence of gaps in freeway speed-density and flow-density data and have suggested that discontinuous functions are necessary to properly describe “observed” traffic behavior. This paper investigates the flow-occupancy (spot-density) relationship using an extensive data set collected on the Queen Elizabeth Way in Ontario. Daily time-traced plots of 5-minute average flow rates versus occupancy were analyzed. Results indicate that there is another interpretation of gaps in data, which does not imply a discontinuous function, but rather, an inverted V shape (continuous, but not continuously differentiable). Three conclusions were reached: (a) it is essential to provide details of data collection locations if one is to know whether a particular pattern in resulting data represents a “true” relationship, or just the specifics of a particular place; (b) there are clear advantages to examining daily time traces of traffic behavior, rather than relying on scatter diagrams of numerous days of accumulated data; and, (c) previously documented arguments for a discontinuous flow-occupancy relationship do not seem convincing, because knowledge of daily operations at a particular location could easily explain the occurence of gaps in the data.     

Empirical macroscopic evaluation of freeway merge-ratios

This paper is concerned with the macroscopic merging behavior of traffic at fully congested freeway merges, where a queue is present at all (upstream and downstream) approaches. An existing theory states that this behavior is dictated by a fixed ratio between the two upstream merging flows, denoted as the merge-ratio. It has been further conjectured that the merge-ratio is equal to the capacity-ratio. This paper presents an effective method to estimate merge-ratios from extensive historical traffic data. The archived traffic data in the California PEMS (Performance Measurement System) from January 2004 to June 2008 are used to estimate merge-ratios at 15 different freeway-to-freeway merge sites (via connectors). Findings show that merge-ratios can be reasonably estimated by the ratios between the numbers of lanes on the merging approaches (lane-ratio), which is typically similar to the capacity-ratio. However, residual differences between merge-ratios and lane-ratios suggest that there are probably other influencing factors.