Concrete Lining Research Articles

Damage Simulation Analysis of Canal Concrete Lining Plates Based on Temperature-Stress-Water Load Coupling

Forming an important component of water conservation infrastructure, canal concrete linings are often subjected to damage to different degrees under the combined action of many factors (temperature, stress, water load, etc.) during construction or later operation. Here we explore the temperature and stress changes in the lining plate under different temperatures and water loads and determine the most unfavorable position (where the stress is more concentrated or the stress value is the largest) of the whole canal lining plate to provide guidance for the subsequent design, construction, and maintenance of canal linings. This paper takes a large irrigation district canal lining project in Henan Province, China as an example and uses ABAQUS finite element software to simulate the temperature and stress fields of the canal concrete lining plate under the combined actions of temperature, stress and water load. The results show that under both conditions of no water or water load, the temperature distribution is more uniform in the middle area of the canal bottom slab, and the temperature of the sunny side slope is higher than that of the shady side slope. The stress values of the lining plate and the bottom plate at the slope foot of the canal are large. Under the action of water load, the maximum stress of the right slope foot of the canal concrete lining plate reaches 2.38 MPa. Furthermore, the validity of the model is verified by comparing the error values, and parameters such as the elastic modulus and Poisson’s ratio were found to have a large influence on the sensitivity of the model. The results can be used as a reference for further research on canal concrete lining construction quality control.

Failure mechanism and treatment measures of supporting structures at the portal for a shallow buried and asymmetrically loaded tunnel with small clear-distance

The construction of a tunnel portal faces the challenges of complex geological conditions, such as shallow burial and asymmetrical loading. In addition, the adverse effects of factors such as the layout form of the tunnel must also be considered. Thus, the construction of portals has always been the focus of tunnel engineering. Under the coupling of multiple adverse factors, such as complex geological conditions and special layout form, the tunnel portal is prone to excessive deformation, supporting structural cracking, and even collapse during excavation. In this study, a shallow buried and asymmetrically loaded tunnel with a small clear-distance in northwest China was considered as an engineering case. To address the distresses of slope instability, peeling off and block falling of primary support concrete, and cracking of secondary lining concrete in the tunnel portal construction, combined with field investigations, statistical analysis, numerical simulation, and deformation monitoring, the failure mechanism of supporting structures was deeply studied and corresponding treatment measures were proposed. The research results indicated that loose and broken gravel soil in the shallow buried section, asymmetrical loading, surface water infiltration, and short construction spacing between the two tunnels were the main triggers of supporting structures failure. Affected by topographic bias, the loose load generated by the surrounding rock on the deeply buried side squeezed the entire tunnel to the shallow buried side after portal excavation. This deformation trend became more significant after the gravel soil deteriorated by water immersion. The retaining wall produced a clockwise rotation deformation around the wall corner in the process of limiting the tunnel deviation, and the local wall body cracked owing to excessive tensile stress. The primary support concrete and secondary lining concrete produced excessive asymmetrical deformation because of significant asymmetrical loading. Concrete with excessive deformation was cracked by obvious tensile or shear stresses. The subsequent tunnel excavation had a significant negative impact on the stability of the prior tunnel. Combining the failure mechanism of the supporting structures and the characteristics of the continuous development of cracks, the treatment measures of ‘stabilize the stratum first and then treat the cracks’ were proposed, including the backfilling and tamping the shallow buried side at tunnel portal, reinforcing the interlaid rock by ground surface grouting, setting intercepting ditch at the slope top, and staggering a certain safe excavation distance between the following tunnel and the prior tunnel. Field monitoring and patrol inspection results indicated that the proposed treatment measures achieved the expected results. The research results can provide corresponding construction experience and suggestions for similar projects in future.

Uphill excavation of an escalator barrel between operational underground platforms

A new underground triple escalator has been provided at Bank Station in London as part of a major capacity upgrade project. Unusually the inclined excavator tunnel was excavated uphill rather than downhill due restricted access. Using a sprayed concrete lining and no pilot tunnel, it was a first in the UK for a triple escalator. The new escalator intercepted several existing structures which had to be backfilled and then broken out, some just 0.5 m from operational Tube lines. This paper sets out design considerations, construction sequence decisions, operational risk management and discusses the existing assets’ response to uphill tunnelling based on a comprehensive monitoring scheme.

A Primary Support Design for Deep Shaft Construction Based on the Mechanism of Advanced Sequential Geopressure Release

The construction of 1500 m depth shaft in Xincheng Gold Mine, China, faces complex stress conditions such as high geostress (>50 MPa), high ground temperature (>50 °C), high water-pressure (>9 MPa), and highly corrosive. Traditional deep shafts excavated by the sinking and lining method cannot adapt to high geostress problems, such as rock bursts and large deformations, etc., in the deep shaft construction process. To avoid and adjust the high geostress induced the rockburst and large deformations, the mechanism of the advanced sequential geopressure release (ASGR) has been proposed for the ground control in deep shaft construction. In this paper, the safe distance between the concrete lining and the shaft excavation face is determined based on the ASGR mechanism, which can provide the space for geopressure release, and primary support based on rock mass quality and numerical simulation was employed to control the geopressure and deformation. A new support scheme for the deep shaft is proposed, using long bolts to restrain severe deformations, metal mesh, and a double reinforcement bar to improve the induced stress distribution. According to the results, the construction scheme of deep shaft has been improved, and the safe support distance of the proposed scheme is determined to be 12 m, with an interval of three excavation cycles. Compared to the original scheme of shaft lining after excavation, the proposed scheme based on the ASGR mechanism can effectively improve the geopressure release and benefit from controlling the rockburst and large deformation of deep shaft induced by high geostress conditions. The stress distribution in the lining is more uniform, and safety factor of the lining is increased to 2.0, which is benefit the long-term stability of deep shaft.

Study on Parameter Influence of New Composite Lining of Water Conveyance Tunnel Under High Internal Water Pressure

A new type of composite lining structure consisting of segments, steel pipes, and concrete lining can be adopted in the water conveyance tunnel to bear large internal water pressure. However, there is still no effective analysis model and calculation method for the parameter influence effect of this new composite lining. In this paper, the load structure method and the elasticity theory are adopted, the stress analysis model and theoretical calculation method of a new type of composite lining of water conveyance tunnel are given, and the influence law of lining structure parameters is studied. Each part of the shield assembled lining is regarded as a stressed spring, and a formula for calculating the equivalent elastic modulus of the overall structure at the joint of the lining under partial tension and partial compression is given. The stress and deformation of each layer of lining are deduced based on the theory of thick-walled cylinders. According to the actual project, the rationality of the calculation method is verified by comparing the results of finite element analysis, and the influence of the thickness of intermediate concrete lining and inner lining parameters on the distribution of force transmission among lining layers is further analyzed. The results show that the radial displacement and circumferential stress of each layer of lining structure decrease with increasing the thickness of the concrete lining. The larger the elastic modulus of the inner lining material is, the smaller the radial displacement of each lining structure will be, but the circumferential stress of the inner lining will increase. In addition, when the thickness of the steel pipe lining is reduced or the internal water pressure is increased, the circumferential stress and radial displacement generated by the inner lining will increase. This analysis model and method considering the deformation coordination relationship solves the problem of setting the parameters of the lining structure and has obvious advantages in the calculation of the stress and deformation of the new composite lining water conveyance tunnel structure, which can provide a theoretical basis for related engineering design.

Characteristics of Vibration Waves Measured in Concrete Lining of Excavated Tunnel during Blasting in Adjacent Tunnel

The effect of a blasting vibration from an excavating tunnel on an adjacent excavated tunnel is of great importance for the stability and security of twin tunnels. Due to the relatively small distance between the tunnel face of the excavating tunnel and the concrete lining of the excavated tunnel, the impact of blasting could be significant and should be considered in a practical project. In order to control the blasting scales during the excavation of one tunnel and minimize the effect of blasting on the adjacent one, research based on field-blasting tests performed on twin tunnels is presented in this study. The particle velocities on the concrete lining of the excavating tunnel caused by blasting from the adjacent excavated tunnel were measured and analysed during six rounds of blasts. According to the measured vibration waves, it was clear that the peak particle velocity (PPV) from each blast was always induced by cut blasting, therefore, the maximum vibration due to each blast was mainly dependent on cut blasting. The measured maximum PPV for all the blasts was 15.55 cm/s, corresponding to a maximum tensile stress of 1.44 MPa observed on the concrete lining, which was smaller than the tensile strength of the concrete lining, in accordance with the one-dimensional elastic-wave theory. Moreover, the attenuation of the vibration waves varied in different regions, and they could be utilized to demonstrate the impact characteristics of the blasting; e.g., the particle velocities in the region along the excavating direction were 1.12 to 1.79 times larger than those in the region opposite to the excavating direction, and the difference increased with the increasing distance to the blasting source. The particle velocities on the side of the excavated tunnel close to the excavating tunnel were larger than those on the other side of the excavated tunnel. However, the particle velocities of the two aforementioned regions were similar when the distance between the measuring point and the blasting source was more than 6 m in the longitudinal direction of the tunnels. Furthermore, the measured vibration waves could be used to evaluate and improve the blast designs of tunnelling with the drill-and-blast method.

Integrated Interpretation of the Results of Long-Term Geotechnical Monitoring in Underground Tunnels Using the Electromagnetic Radiation Method

Electromagnetic radiation (EMR) technology makes it possible to evaluate changes in the stress-strain state (SSS) in the “tunnel lining-enclosing rock mass” system at a high level of interference, and to create schemes of long-term EMR control in tunnels (geotechnical monitoring systems). The issues of the variations in EMR signals are extremely important for monitoring systems: based on anomalous deviations from the normal regime one can draw conclusions about changes in the SSS, leading to geodynamic phenomena (e.g., rock bursts). This article presents data obtained during laboratory studies on samples and field studies in transport tunnels. Also, some results of long-term geotechnical monitoring by a set of methods is presented: EMR and tensometry of the tunnel lining, both methods are in the automatic mode. The ability of an EMR control system to respond to earthquakes affecting tunnel structures is shown. An analysis of long-term EMR studies was conducted, which showed the periodic oscillation of the “tunnel lining-enclosing rock mass” system. In a stable compressed state, minima of EMR pulses are recorded; when the rock mass and lining material are stretched, charges are separated on the edges of micro-defects and EMR increases; complete separation of the edges of micro-defects leads to the termination of intense EMR. The same occurs in the opposite direction during the compression of micro-defects and micro-fractures in the rock mass and concrete lining. The periods of compression and expansion are closely related to temperature fluctuations. The results differ in detail and, therefore, in to be more confident, additional studies are needed in various host rock massifs and types of tunnel lining.

Vouchers for Improving Sanitation: A Step toward Stopping Open Defecation.

Vouchers for Improving Sanitation: A Step toward Stopping Open Defecation.

Refractory materials of metallurgical furnaces with the addition of silicon production waste

Currently, there are problems with the operation of metallurgical furnaces at high process temperatures. In the melting zone, the destruction of the side lining and the hearth slab lining in the contact zone of the melt is especially common due to the chemical aggressive environment from the processes of interaction and reactions between the components and mechanical wear as a result of the impact of the tool during maintenance. In most cases, refractory materials do not provide stable operation of the metallurgical unit, they have low operational characteristics. Of scientific and technical interest is the use as a modifying additive for a refractory mixture of technogenic microsilica — waste in the production of metallurgical silicon. Microsilica is a unique finely dispersed composite material with high strength, low density, and with a highly developed particle surface, which further gives refractory products improved strength and durability properties. As part of the study, a series of experiments were conducted with microsilica waste in the production technology of general-purpose fireclay products, as well as in the production technology of refractory concrete mix for monolithic concrete linings and the manufacture of refractory products. It has been established that the optimal value of the content of microsilica in the total mass of general-purpose fireclay products is in the range from 3 to 7%, and in the composition of a dry refractory concrete mixture from 1 to 2%, which does not lead to a decrease in the quality characteristics of the products. Tests of samples have shown that the use of microsilica in the production of refractories can significantly improve properties such as heat resistance and fire resistance, while reducing the cost of production. The obtained results of experiments conducted with the initial microsilica and its behavior in refractory mixtures indicate that the proposed fine composite material can be used in refractory products and introduced into technical standards.

Construction Quality Evaluation of Large-Scale Concrete Canal Lining Based on Statistical Analysis, FAHM, and Cloud Model

As an important component of water conservancy infrastructure, canals help improve the uneven distribution of regional water resources. However, in their construction and operation processes, which are affected by a variety of complex factors, canal linings often produce various problems that greatly reduce their overall quality and lead to water resources being wasted. To evaluate and determine the factors and key procedures affecting the construction of concrete canal linings so as to improve their quality, an evaluation mechanism based on statistical analysis, the fuzzy attribute hierarchical model (FAHM), and the cloud model is proposed in this paper. Using this method, we first determine the problems affecting the construction quality of canal linings through statistical analysis, through establishing a questionnaire based on these factors; then, we use FAHM to identify the main quality problem factors; finally, we use the cloud model to analyze the overall construction quality of concrete canal linings. The quality evaluation and key construction procedures are determined, and a case study is conducted taking a canal lining project in China as an example, for which the final evaluation result is grade II. At the same time, a comparative study is carried out using the AHP and cloud models. The results indicate that the proposed method is more reasonable and feasible than existing methods, thus laying a foundation for the follow-up quality control of canals.

Degradation Law and Service Life Prediction Model of Tunnel Lining Concrete Suffered Combined Effects of Sulfate Attack and Drying-Wetting Cycles.

The present study explored the degradation law and service life prediction of tunnel lining concrete with different mineral admixtures under coupled actions of sulfate attack (SA) and drying–wetting (DW) cycles. The deterioration resistance coefficient (DRC) of compressive strength and influence coefficients of sulfate concentration, mineral admixture content, water/binder (w/b) ratio, and curing regime on DRC were studied. After that, a new service life prediction model based on damage mechanics was developed and analyzed. Results show that, by increasing the DW cycles, the DRC first increases and then decreases. DRCs of Ordinary Portland cement (OPC), fly ash (FA), and ground granulated blast-furnace slag (GGBS) concrete linearly decrease with the increase of sulfate concentration, while the silica fume (SF) concrete displays a two-stage process; by increasing the admixture content, the DRCs of FA and GGBS concrete exhibit two distinct stages, while the SF concrete depicts a three-stage process; increasing the w/b ratio linearly decreases the DRC; the DRC of curing regime was sequenced as standard curing (SC) > fog curing (FC) > water curing (WC) > same condition curing (SCC). Based on the experimental results, the service life prediction model is applied and validated. The validation results show that the proposed model can accurately predict the lifetime of concrete with different mix proportions. Furthermore, it is found that the mineral admixture can effectively improve the lifetime of concrete, and the composite mineral admixture is more effective than a single mineral admixture in improving the lifetime of concrete.

Analytical modeling of complex contact behavior between rock mass and lining structure

Based on the nondestructive test data of operating railway tunnels in China, this paper summarizes the basic characteristics of the complex contact behavior between the rock mass and lining structure. The contact modes are classified into dense contact, local non-contact, and loose contact. Subsequently, the corresponding mechanical model for each contact mode is developed according to its mechanical characteristics using the complex variable method. In the proposed mechanical model, a special algorithm is introduced to detect whether the local non-contact zone is re-contacted. Besides, a novel conformal mapping method is also proposed to accurately calculate the mechanical response of the concrete lining. Finally, the accuracy of the proposed method is verified by comparing it with the finite element method (FEM). Several parameter investigations are conducted to analyze the effects of different contact modes on the rock–lining interaction. The results show that: (i) the height of the local non-contact area does not have a significant effect on the contact stress distribution if no re-contact occurs; (ii) backfill grouting can reduce the local stress concentration caused by poor contact modes; and (iii) reducing the friction coefficient of the interface can lead to a more uniform distribution of internal forces in the concrete lining.

Seismic retrofitting of rubble masonry tunnel: evaluation of steel fiber shotcrete or inner concrete lining alternatives

Seismic retrofitting of rubble masonry tunnel: evaluation of steel fiber shotcrete or inner concrete lining alternatives

Multiscale modeling for fire induced spalling in concrete tunnel linings based on the superposition-based phase field fracture model

In view of the global–local property and multiscale characteristics of spalling behavior in tunnel lining, superposition-based phase field fracture model is introduced within a framework of concurrent multiscale modeling for fire-induced spalling process in tunnel lining. After formulating the governing equations for the coupled thermo-mechanical-phase field model, the numerical solutions by the superposition method or the so-called s-version method are provided. Subsequently, taking the tunnel segment as the demonstration component, the s-version model for the tunnel lining is developed, and the spalling behavior is observed at both macroscopic and mesoscopic scales. On the basis of the s-version model of tunnel segment, the single-scale and multiscale stratum-structure models are further developed, by taking into account the interaction between tunnel structure and surrounding stratum, the heterogeneous microstructure of concrete material, and the formation of local damage in the critical region.

Suitability Evaluation of the Lining Form Based on Combination Weighting–Set Pair Analysis

Aiming at the many uncertain factors in the suitability evaluation of reinforced concrete lining of high-pressure pipelines, the set pair analysis (SPA) theory is used to establish the suitability evaluation model. By summarizing the key influencing factors of typical lining design criteria, five suitability evaluation indices are determined from three criteria, i.e., the minimum overburden criterion, the minimum principal stress criterion, and the hydraulic fracturing criterion. In order to fully consider the subjective and objective factors, the combination ordered weighted averaging (C-OWA) operator and the criteria importance through intercriteria correlation (CRITIC)-entropy weighting model (EWM) were used to construct a combination weighting method, and the weight coefficients of each index were comprehensively determined. Based on the SPA theory and calculation rules, combined with the lining suitability grading criteria, the five-element connection degree of each index and the comprehensive connection degree of each working point were calculated. In this study, the model is applied to the suitability evaluation of reinforced concrete lining at each drilling point of the high-pressure pipeline of a pumped storage power station (PSPS) in Shanxi Province. The results show that the proposed model consisting of subjective weight and objective weight can effectively avoid the error caused by a single weight method, which improves the evaluation sensitivity and rationality.

Analytical model for deep tunnel with an adaptive support system in a viscoelastic-burger's rock

This paper presents an exact closed-form solution for the mechanical behavior of a linear viscoelastic Burger's rock around a circular tunnel supported by an adaptive support system. The tunnel consists of a bilayer concrete/stress-control element. The stress-control element is achieved with a hydraulic system deforming at constant pressure to a maximum displacement and becoming practically rigid after the initial deformation phase. Analytical equations are provided for the tunnel boundary displacement and the pressure exerted by the rock on the concrete liner. Results obtained from the analytical solution are validated by comparing them to numerical modeling results. A parametric study is performed to investigate the effects of installation time, yield strength of the stress-control element, and support deformation capacity on the tunnel response. Based on the closed-form solution, the yield capacity of the bilayer concrete/stress-control element is compared to that of the traditionally used bilayer concrete/compressible grout. The results show that the variation of tunnel response with installation time, yield strength, and deformation capacity of the yielding support are not monotonic. There is an optimal thickness of the yielding layer for given yield strength, beyond which the yield efficiency will not further increase. Notably, the results highlight the greater yield efficiency of the bilayer concrete/stress-control element than the bilayer concrete/compressible grout, particularly in tunnels with a relatively thin annulus void and using a yielding layer with relatively low yield strength.

Radioaktivní prameny v Praze-Čimicích

Groundwater inflows showing notable natural radioactivity have been found at the northern end of the Holešovice cable tunnel close to the Čimice Grove. This groundwater originates from the Barrandian Neoproterozoic slates of the Blovice accretionary complex, Belt I (Šárka-Zbiroh Belt) at depths approximately 100 meters below the surface, occurring along 50 meter profile of the cable tunnel. Water springs are dispersed in the spring area, with the total discharge of 2 L/s. Groundwater is cold (T ~ 11.1 – 12.3 °C), neutral (pH ~ 6 – 7.48), suboxic to oxic (Eh (ORPH) ~ 177 up to 418 mV), of a hydrochemical type Ca-Mg-HCO3, total mineralization being around 702 mg/L. Radon activity (222Rn) varies between 415 and 1195 Bq/L and radium activity (226Ra) ranges between 0.18 and 5.3 Bq/L. Activities of Rn and Ra are relatively high. Currently, this is the most radioactive water within Prague agglomeration. This water is relatively aggressive as well, causing damage to the concrete lining of the cable tunnel and also allowing formation of calcite precipitates with an increased radium (226Ra) activity.

A Review on Study of Rehabilitation and Repair Techniques of R.C.C. Building

Abstract: Cement concrete reinforced with steel bars is an extremely popular construction material. One major flaw, namely its susceptibility to environmental attack, can severely reduce the strength and life of these structures. External reinforcement using steel plates have been used in earlier attempts to rehabilitate these structures. The most important problem that limited their wider application is corrosion. This project emphasize on Rehabilitation of R.C.C. structures. The purpose of this project is to highlight the various techniques of repair and rehabilitation methods to be undertaken for structures with defects and deficiencies that necessitate rehabilitation. Repair and Rehabilitation methods currently used are reviewed on the basis of present knowledge and the merits of a holistic system approach. This project focuses on visible symptoms of the problem rather than on invisible problems as well as the possible causes behind them. This project focuses on various techniques and repair materials used for the satisfactory performance of the repaired structure. This project presents an analysis of concrete illnesses, and problems leading to unsatisfactory performance of repaired concrete structure. This project describes the analysis the types of surface preparations that are commonly adopted in Indian conditions. This project highlights the problem of reinforcing steel corrosion in concrete structures and attempts to provide the remedial measures available in design to mitigate the effects of corrosion. In view of these limitations the various types of coatings are available and the precautions to be taken in the selection of coatings systems are also discussed. This also highlights the importance of epoxy resins and various methods of epoxy in the construction applications such as repairing of cracks, patching, grouting of concrete, structural adhesives and anti-corrosive linings etc. The conclusive part deals with cost comparison between present approximate estimated cost of new building & rehabilited building.

Mechanical behaviour of continuous girder bridge with corrugated steel webs constructed by RW

Abstract Rapid construction of ripple web (RW) is a new construction technology that can be applied to the prestressed concrete (PC) box girder bridge with corrugated steel webs (CSWs). In order to analyse the mechanical behaviour in the construction process when the RW method is applied, the main bridge of Zhao-Jun Yellow River Super Large Bridge was adapted as the engineering background, and a three-dimensional simulation finite element model was established. Thereafter, detailed mechanical analyses were carried out for CSWs, top concrete and bottom concrete, lining concrete, temporary support and other structures in the construction process when the RW method was used. The results reveal the excellent quality of the mechanical properties of the structure, thus indicating the structure’s safety and reliability. This study can provide a reference for similar research and have a positive impact on the further promotion of the RW method for application in the continuous girder bridge with CSWs.

Modified AK-MCS method and its application on the reliability analysis of underground structures in the rock mass

This work aims at proposing the methodology on the basis of the extension of the famous reliability analysis, joining the Kriging and Monte Carlo Simulation (AK-MCS) metamodeling technique for analyzing the long-term stability of deep tunnel support constituted by two layers (a concrete liner covered with a compressible layer). A novel active learning function for selecting new training points enriches the Design of Experiment (DoE) of the built surrogate. This novel learning function, combined with an appropriate stopping criterion, improves the original AK-MCS method and significantly reduces the number of calls to the performance function. The efficiency of this modified AK-MCS method is demonstrated through two examples (a well-known academic problem and the case of a deep tunnel dug in the rock working viscoelastic Burgers model). In these examples, we illustrate the accuracy and performance of our method by comparing it with direct MCS and well-known Kriging metamodels (i.e., the classical AK-MCS and EGRA methods).