Search results

The microseismic monitoring technique has great advantages on identifying the location, extent and the mechanism of damage process occurring in rock mass. This study aims to analyze distribution characteristics and the evolution law of excavation damage zone of surrounding rock based on microseismic monitoring data.

In situ test using microseismic monitoring technique is carried out in the large-span transition tunnel of Badaling Great Wall Station of Beijing-Zhangjiakou high-speed railway. An intelligent microseismic monitoring system is built with symmetry monitoring point layout both on the mountain surface and inside the tunnel to achieve three-dimensional and all-round monitoring results.

Microseismic events can be divided into high density area, medium density area and low density area according to the density distribution of microseismic events. The positions where the cumulative distribution frequencies of microseismic events are 60 and 80% are identified as the boundaries between high and medium density areas and between medium and low density areas, respectively. The high density area of microseismic events is regarded as the high excavation damage zone of surrounding rock, which is affected by the grade of surrounding rock and the span of tunnel. The prediction formulas for the depth of high excavation damage zone of surrounding rock at different tunnel positions are given considering these two parameters. The scale of the average moment magnitude parameters of microseismic events is adopted to describe the damage degree of surrounding rock. The strong positive correlation and multistage characteristics between the depth of excavation damage zone and deformation of surrounding rock are revealed. Based on the depth of high excavation damage zone of surrounding rock, the prestressed anchor cable (rod) is designed, and the safety of anchor cable (rod) design parameters is verified by the deformation results of surrounding rock.

The research provides a new method to predict the surrounding rock damage zone of large-span tunnel and also provides a reference basis for design parameters of prestressed anchor cable (rod).

Damages occur in all structures due to several reasons. Research in the area of damage detection has been of interest to the researchers for several years. Damage detection methods help in early detection and hence early repair and rehabilitation of structures. In this paper, a graphical method has been implemented to detect and quantify the damage. Further, in this work, the method has been generalised to solve the damage detection in all beam structures, independent of variations in geometric or material characteristics of the structural system. The frequencies are non‐dimensioned as frequency ratios and are used in the studies. Detailed studies have been performed to arrive at the generalised method. The abilities of the method have been highlighted using the numerical simulation results.

Large displacement misalignment under the action of active faults can cause complex three-dimensional deformation in subway tunnels, resulting in severe damage, distortion and misalignment. There is no developed system of fortification and related codes to follow. There are scientific problems and technical challenges in this field that have never been encountered in past research and practices.

This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation based on the open-cut tunnel project of the Urumqi Rail Transit Line 2, which passes through the Jiujiawan normal fault. The test simulated the subway tunnel passing through the normal fault, which is inclined at 60°. This research compared and analyzed the differences in mechanical behavior between two types of lining section: the open-cut double-line box tunnel and the modified double-line box arch tunnel. The structural response and failure characteristics of the open-cut segmented lining of the tunnel under the stick-slip part of the normal fault were studied.

The results indicated that the double-line box arch tunnel improved the shear and longitudinal bending performance. Longitudinal cracks were mainly distributed in the baseplate, wall foot and arch foot, and the crack position was basically consistent with the longitudinal distribution of surrounding rock pressure. This indicated that the longitudinal cracks were due to the large local load of the cross-section of the structure, leading to an excessive local bending moment of the structure, which resulted in large eccentric failure of the lining and formation of longitudinal cracks. Compared with the ordinary box section tunnel, the improved double-line box arch tunnel significantly reduced the destroyed and damage areas of the hanging wall and footwall. The damage area and crack length were reduced by 39 and 59.3%, respectively. This indicates that the improved double-line box arch tunnel had good anti-sliding performance.

This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation. This system increased the similarity ratio of the test model, improved the dislocation loading rate and optimized the simulation scheme of the segmented flexible lining and other key factors affecting the test. It is of great scientific significance and engineering value to investigate the structure of subway tunnels under active fault misalignment, to study its force characteristics and damage modes, and to provide a technical reserve for the design and construction of subway tunnels through active faults.

The purpose of this paper is twofold: first, to investigate the flood impact on a detached dwelling based on physical attributes related to the positioning, form and orientation of the house, and second, to investigate the effectiveness of property-level protection (PLP) to mitigate the direct structural damage of the house and the degree of floodwater ingress within the house.

The methods included modelling and simulation within the ANSYS Fluent® computational fluid dynamics software. Flooding scenarios with constrained parameters using theoretical modelling methods/tools were used to test the research hypotheses. Therefore, the results obtained will match the what-if scenarios considered if/based on the standard equations and assumptions made in the idealised model.

It was found that the position, orientation and form of an individual dwelling with brick and block construction informs the impact of the applied pressure on the structure and water ingress. Increase in pressure on the structure was noted from 0.3 m. All examined PLP mitigated the risk of structural damage if applied in consideration with other interventions e.g. mortar sealing. The use of non-return valves could potentially increase the pressure on the structure, but was also found to be effective in reducing water ingress. Findings should be considered in conjunction with the assumptions and exceptions of this study.

The limitations of this study are that the findings are based on an idealised model of a single detached house, with no landscape obstruction to the watercourse. This mathematical approach concerned with developing the normative models may therefore not fully describe the real-world complex phenomena. But it provides the first vision and an objective basis to answer the questions under study, and to propose usable outputs. Flooding caused from internal sources (e.g. bursting of pipes, roof leaks) or seepage from the ground and moisture through the walls were excluded. Building content was not modelled.

Common property-level flood interventions are typically tested to mitigate water ingress to the house. This study extends this approach to include the prevention of structural damage to the external walls; this can help to avoid the indiscriminate use of property-level flood prevention solutions without full understanding of their degree of effectiveness or impact on the building’s structural integrity. This study is practically significant because it provides outputs and means to examine which intervention(s) are better for delivering flood protection to a standard brick/block detached house type. This knowledge is highly beneficial for relevant stakeholders who can use it to deliver effective property-level flooding resilience measures.

The study provides useful insights for property owners and building professionals to explore suitable, cost-effective single property-level protection against flooding. Furthermore, the effective implementation of interventions can be used to achieve a customised, “fit for purpose” resilience retrofit.

Frost damage is well-known as the main cause of roof tile deterioration. The purpose of this paper is to develop an analytical model for predicting the deterioration process under certain climatic conditions. This paper describes the results of a field survey conducted to acquire fundamental information useful to this aim.

A field survey of roof tile damage by freezing was conducted in an old temple precinct in Kyoto, Japan. Using detailed observations and photographic recordings, the damage progress was clarified. To examine the impact of climatic conditions upon the damage characteristics, weather data and roof tile temperatures were measured and logged in the winter season.

The deterioration process was observed under the climatic conditions associated with the measured temperature of the roof tiles. In particular, it was revealed that the orientation has a significant influence on increasing or decreasing the risk of frost damage. For certain distinctive forms of damage, the deterioration mechanisms were estimated from the viewpoint of the moisture flow and temperature distribution in the tile.

This study contributes to the elucidation of the mechanism behind frost damage to roof tiles. The findings will guide the construction of a numerical model for frost damage prediction.

This paper aims at the problem of surrounding rock excavation damage zone of tunneling in the rich water region, this paper aims to propose a new seepage-stress-damage coupling model and studied the numerical algorithm. This reflects the characteristics of rock damage evolution, accompanied by plastic flow deformation and multi-field interaction.

First of all, rock elastoplastic damage constitutive model based on the Drucker–Prager criterion is established, the fully implicit return mapping algorithm is adopted to realize the numerical solution. Second, based on the relation between damage variation and permeability coefficient, the rock stress-seepage-damage model and multi-field coupling solving iterative method are presented. Finally, using the C++ language compiled the corresponding programs and simulated tunnel engineering in the rich water region.

Results show that difference evolution-based back analysis inversed damage parameters well, at the same time the established coupling model and calculating program have more advantages than general conventional methods. Multiple field coupling effects should be more considered for the design of tunnel support.

The proposed method provides an effective numerical simulation method for the construction of the tunnel and other geotechnical engineering involved underground water problems.

Wavelets are being increasingly used for damage diagnostics. The purpose of this paper is to present an algorithm that uses the wavelet transform for detecting mixed-mode, also known as combined mode, cracks in large truss structures.

The mixed-mode crack is modeled by superposing two damage modes, and this model is combined with a finite element model of the truss. The natural modes of the truss are processed through the wavelet transform and then used to determine the damage location. The influence of multiple parameters such as truss geometry, crack geometry, number of truss members, orientation of truss members, etc. is investigated as part of the study.

The proposed damage detection algorithm is found to be successful in detecting single mode as well as mixed-mode cracks even in the presence of significant end effects, and even when a relatively coarse sampling of natural modes is used. Results from multiple simulations that involve three commonly used truss structures are presented. A correlation between damage severity and the magnitude of wavelet coefficients is observed.

The proposed algorithm is found to be successful in accurately detecting damage, but direct determination of damage severity is found to be challenging.

There has been a significant increase in flooding in the UK over the past ten years. During this time, Government policy has moved from investment in flood defences towards encouraging property owners to take responsibility for reducing the impact of flooding. One of the ways in which this can be achieved is for homeowners to adapt their properties to flood risk by implementing property level flood risk adaptation (PLFRA) measures. While there has been some attempt to develop an understanding of the benefits of such measures, these previous studies have their limitations in that the intangible benefits have not been fully considered. As such, there remains a need for further development of these studies towards developing a more comprehensive understanding of PLFRA measures. It is against this background the purpose of this paper is to present a conceptual cost benefit analysis (CBA) framework for PLFRA measure. This framework brings together the key parameters of the costs and benefits of adapting properties to flood risk including the intangible benefits, which have so far been overlooked in previous studies.

A critical review of the standard methods and existing CBA models of PLFRA measures was undertaken. A synthesis of this literature and the literature on the nature of flooding and measures to reduce and eliminate their impacts provides the basis for the development of a conceptual framework of the costs and benefits of PLFRA measures. Within the developed framework, particular emphasis is placed on the intangible impacts, as these have largely been excluded from previous studies in the domain of PLFRA measures.

The framework provides a systematic way of assessing the costs and benefits of PLFRA measures. A unique feature of the framework is the inclusion of intangible impacts, such as anxiety and ill health, which are known to be difficult to measure. The study proposes to implement one of the stated preference methods (SPM) of valuation to measure these impacts, known as the willingness to pay method, as part of a survey of homeowners. The inclusion of these intangible impacts provides the potential to develop a more comprehensive understanding of the benefit cost ratio (BCR) for different stakeholders. The newly developed CBA conceptual framework includes four principal components: the tangible benefits to insurers; the tangible benefits to the government; the tangible benefits to homeowners; and the intangible benefits to homeowners.

This tool offers the potential to support government policy concerned with increasing the uptake of PLFRA measures through increasing the information available to homeowners and thereby supporting the decision-making process.

The work presented here is based on the assumption that all non‐linear properties, appearing in the evolution of magnetic fluids, are a complex system. Then, the establishment of a relationship between the structural changes in the geomagnetic field and the occurrence of earthquakes by employing the so‐called infrastructural informational analysis is undertaken. From the authors’ previously published serial work, it was found that the “zero isotropic zone” is a “discernible characteristic indication” which can be applied to the predictions of earthquakes with great practical effect.

Flood damage to domestic properties can be considered as a function of two key factors, that is, the flood characteristics and characteristics of the property. A thorough literature review identified that little or no consideration is given to the characteristics of flood when assessing flood‐damaged domestic properties. This paper presents the perceptions of 289 building surveyors regarding flood characteristics as part of a 2‐year research project to benchmark the assessment of flood‐damaged domestic properties in the UK. Surveyors perceived the sewage, fasciae and contaminant content, and depth of the floodwater. Findings also revealed that methods to determine these factors were primarily a function of individual subjective perceptions. Definitive guidance is therefore, needed to minimise variations in subsequent repair and reinstatement works.