Evaluation of grouting in tunnel lining using impact-echo

The shield tunneling method is commonly used for tunnel excavation. After the excavation, curved reinforced concrete members are used to support the surrounding ground/rock and seal the tunnel. Grouting is performed to provide adhesion between the concrete members and the ground. The assessment of the grouting quality by pull-out tests and core sampling is destructive, time-consuming and expensive. In the present case, impact-echo was applied as a means of non-destructive and time-effective evaluation. Excitation was conducted by an impact hammer on the surface of several concrete plates and the reflection was acquired by a low frequency accelerometer. Combined use of time domain characteristics, spectral content and wavelet transform reveal the effectiveness of grouting and indicate that impact echo is valuable for quick and reliable assessment of grouting in such cases.     

Lessons Learned from Field and Laboratory Testing of a DBR Project

Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2?years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars.     

注浆技术在高炉护炉中的应用

注浆技术已经在建筑、矿山、桥梁、道路等行业得到广泛的应用，梅钢炼铁厂将此技术应用于1号、3号高炉的后期长寿护炉的技术攻关中，梅山设备公司不断征求用户的意见，根据用户高炉长寿的实际需求，经过多次摸索总结出一套实际可靠的操作方法，在实际应用中创造出良好的护炉效果和经济效益。     

蓄水状态混凝土堵漏措施浅议

混凝土蓄水构筑物出现渗漏水情况时，可采取水泥灌浆或化学材料表面处理两种措施。     

太原市汾河城区治理美化工程关键工程措施的成功采用

汾河治理美化工程在渗透性很高的河道砂土地层上成功蓄水是由于采用了高喷防渗墙和橡胶坝等先进技术。本文对有关技术参数的评述，对工程实践有一定的参考价值。     

高性能灌浆材料研究及应用

本文首次讨论了高性能灌浆材料 ,着重介绍了浆体配合比的设计和试验。研究结果表明 :高性能灌浆材料具有流动度大、强度高、无明显收缩或泌水现象 ,可以用于后张法预应力混凝土结构。     

注浆站注浆参数监测系统

介绍一种采用ＭＣＳ－５１单片机和ＰＣ机的注浆参数实时监测系统,给出了单片机测试部分的硬件结构和系统的软件设计。     

Analytical Model for Fracture Grouting in Sand

A conceptual, analytical model has been developed to describe the fracture grouting process in sand. The objective of the model is to improve understanding about this process in sand and to model propagation of the fractures. The results can be used to assess the parameters that control the fracture process. It is assumed that the complicated shape of a fracture in sand can be simplified to a geometrical shape (such as a tube or a plane) as a first approximation. Filtration of the grout appears to have a significant influence on the fracture shape when grout is injected into permeable subsoil such as sand. By assuming a pressure at which a fracture starts and a minimum pressure for propagation, it appeared possible to calculate the width-to-length ratio of the fracture independent of other soil properties. Quantification of the flow inside a fracture and the filtration processes resulted in a model that has been used to study differences in fracturing behavior in model tests and field tests on fracture grouting in sand. It was concluded that the width-to-length ratio of the fractures in a permeable soil decreases if the injection pressure of the grout or the permeability of the grout cake is decreased.     

Control of rock jacking considering spread of grout and grouting pressure

This paper describes a theoretical approach for monitoring fracture dilatancy (or “jacking”) during grouting. From this, a methodology to optimize the grout pumping pressure has been developed, based on the required penetration length (i.e. the distance that the grout spreads from the grout hole into the network of fractures within the rock mass). Empirical rules are put forward to prevent the damage that may result from uncontrolled deformation (Jacking) of the fractures, by limiting either pumping pressure or the injected grout volume, or by a combination of both. The state of the fractures and the spread of the grout when these limits are reached are discussed. The theoretical approach, which is referred to here as the Real Time Grouting Control Method, enables the estimation of grout penetration length or “spread” in real time. This gives an opportunity to monitor fracture dilation as it happens and, for the purpose of this paper, the allowable limits of elastic deformation and jacking have been estimated based on the grout spread. Two case histories are analyzed, for which the physical reaction of the fracture deformation with time and grout spread are determined from the recorded pressure and flow. By comparing the observed physical reaction with the theories for jacking presented here, the Real Time Grouting Control Method has been validated, and it is shown that this theoretical approach is superior to commonly used empirical methods, in that it allows the optimization of the pumping pressure to achieve a given penetration length in the shortest time and with an acceptable fracture dilatancy. This approach is a major step forward in customizing grouting works.