Experimental and numerical investigation of restrained shrinkage of concrete

To promote the understanding of shrinkage related behaviour of concrete used for tunnel linings the experimental and theoretical investigation including numerical and analytical approach was performed on ring-shaped specimens. Overall one analytical (an.) and two numerical models, namely (i) and (ii) were also developed. Models (an.) and (i) considered the restraining steel ring to be rigid, thus not exhibiting any deformation. Numerical model (ii) considered the steel ring to be deformable. The experimental set-up consisted of a large concrete ring with an inner diameter of 120 cm, an outer diameter of 160cm and 20 cm in height. The restraining steel ring was 5.5 cm thick. Two concrete rings were made, namely R1 with a low compressive strength of ~26MPa and the other, R2, with medium compressive strength of ~40 MPa. The strain was measured in the hoop direction on the inner circumference of the steel ring and on the outer circumference of the concrete ring. Concrete rings were subjected to circumferential drying. Numerical model (ii) predicted critical time to the formation of the first crack to be between 13 and 14 days. The experimentally determined critical time is found to be 11 to 13 days with cracks gradually opening over several days. This was indicated by changes in measured concrete and steel strain. Modelled concrete strain just before cracking was between -20 and -30 % 10-6 m m-1 however, measured concrete strain was ~150 % 10-6 m m-1. Modelled steel strain was between -30 and -40 % 10-6 m m-1 while measured steel strain was between -10 and 20 % 10-6 m m-1. These discrepancies, in particular the positive steel strain obtained in experiments, require further investigation and improvements of the experimental set-up

DE_Calibration_DEM_Material

Application of Differential Evolution Algorithm to Calibrate the DEM Cohesive Granular Materia

Tunnel information modelling in most recent form: applying BIM technologies and procedures in tunnelling environment

The importance of information management was recognised in surface construction industry decades ago, and has increasingly being recognised through formal process and laws. Around the world, these laws and codes of practice are currently being drafted and enacted, to reflect the development of software tools and corresponding increasing adoption by industry. This paper deals with specifics of implementing information modelling in tunnelling business utilising BIM (Building Information Modelling) technology developed for buildings as well as similar technology developed for mining industry. Although BIM is recognized initially as a 3D digital representation of physical and functional characteristics of a facility, the real benefits come when complex capability through construction sequencing and even detailed programming (4D) and cost capabilities (5D) are included

Identification Method for Internal Forces of Segmental Tunnel Linings via the Combination of Laser Scanning and Hybrid Structural Analysis

This paper provides a new solution to identify the internal forces of segmental tunnel linings by combining laser scanning and hybrid structural analysis. First, a hybrid structural analysis method for quantifying the internal forces based on displacement monitoring is established, which requires comprehensive displacement monitoring with high precision and a complete trace history. Motivated by the development of laser scanning, two remedial solutions are proposed for typically insufficient engineering conditions, i.e., lack of displacement developing process and poor accuracy of measurements, which is highlighted in this paper. Therefore, with the help of remedial solutions, the structural analysis is able to be adopted with the application of laser scanning. The tool for developing remedial solutions is the first-order theory of slender circular arches. Virtual tests, based on a calibrated finite element model, were performed to verify the feasibility of the presented hybrid analysis and remedial solutions. In addition, parametric analyses were conducted to study the error propagation from laser scanning to the results of hybrid analysis. The resolution and measurement noise of laser scanning were investigated and discussed. On this basis, advice on combining laser scanning and hybrid structural analysis is proposed. Finally, on-site application of the hybrid analysis on an actual tunnel is presented and discussed

Local Acceleration Monitoring and its application in physical modelling of underground mining

A Micro-Electro-Mechanical Systems (MEMS) inertial sensor was introduced to perform Local Acceleration Monitoring (LAM) in a physical model to showcase mining-induced strata movements. To prove the feasibility of LAM, a physical model experiment was performed using four sensors mounted on the roof strata. Acquired acceleration signals were processed by a moving average and median filter, analysed with respective trend variation and fluctuation along with excavation sequence. To identify the movement of roof strata, a key reference was the mid-span section that characterized by adjacent sensors with opposite acceleration change direction. To assess the stability of strata, a clear evidence is the synchronicity loss of two adjacent sensors in terms of acceleration change. In the presented experiment, the first weighting and the fracture position can be predicted 1.5 h prior to final failure. This study represents a novel attempt to apply LAM in a physical modelling experiment and tentatively interpret signals in accordance with strata movement. The proposed LAM-based approach succeeded in identifying the movement and assessing the stability of the strata. Results presented in this paper verify the validity of LAM in terms of noise analysis, sensibility and rationality. This LAM technique is capable of serving as an easy-to-implement, high-precision and low-cost method in mining and geotechnical related physical modelling research