Environmental Engineering: Research @ Brunel

Research published by Brunel staff

Below are recent articles (co-)authored by Brunel academic staff. Please click the title of the article to access the full-text.

• Analyzing strain localization of Chang'E-5 lunar regolith through discrete element analysis
  Wang, S. Y. et al
  Powder Technology, Vol 448, Art No. 120293 (Dec 2024)
  The current understanding of the geotechnical behavior of lunar in-situ resources, particularly lunar regolith (LR), is significantly limited due to its scarcity. To address this gap, this research utilized the morphological characteristics of LR particles obtained from the Chang'E-5 (CE-5) mission to construct numerical simulants using the discrete element method (DEM). This approach was then employed to investigate the mechanical properties of LR. Firstly, high-definition lunar particle images from the CE-5 mission were selected to capture the morphological characteristics and grain size distribution. These morphological characteristics were linked with the rolling resistance parameter and incorporated into the three-dimensional (3D) micromechanical contact model. Additionally, a flexible boundary condition was employed in the triaxial simulation to ensure the evolution of strain localization. The relative particle translation gradient (RPTG) concept was utilized to capture the onset and development of strain localization during the shear process. The results indicated that the numerical lunar simulants can effectively reproduce the mechanical response of LR. Furthermore, at the particle scale, particle shape characteristics play a crucial role in particle rotation and translation during the shear process. This study may establish a foundation for lunar resource exploration and utilization techniques.

• Deformation monitoring at shield tunnel joints: Laboratory test and discrete element simulation
  Mao, M. Y. et al
  Deep underground science and engineering, [early access Apr 2024]
  Shield tunnel, composed of several segments, is widely used in urban underground engineering. When the tunnel is under load, relative displacement occurs between adjacent segments. In the past, distributed optical fiber sensing technology was used to perform strain monitoring, but there is an urgent need to determine how to transform strain into displacement. In this study, optical frequency domain reflectometry was applied in laboratory tests. Aiming at the shear process and center settlement process of shield tunnel segments, two kinds of quantitative calculation methods were put forward to carry out a quantitative analysis. Meanwhile, the laboratory test process was simulated numerically utilizing the discrete element numerical analysis method. Optical fiber, an atypical geotechnical material, was innovatively applied for discrete element modeling and numerical simulation. The results show that the measured displacement of the dial gauge, the calculated results of the numerical model, and the displacement quantitatively calculated from the optical fiber data agree with each other in general. The latter two methods can potentially be utilized in engineering application of deformation monitoring at shield tunnel joints, but need to be further calibrated and adjusted in detail.
  
  The optical frequency domain reflectometry technique is applied in laboratory tests to monitor the shear process and center settlement process of shield tunnel segments. Two kinds of quantitative calculation methods are put forward, and the discrete element numerical analysis method is utilized to verify these two methods. The results show that the measured displacement of the dial gauge, the calculated results of the numerical model, and the displacement quantitatively calculated from the optical fiber data agree well with each other. image
  
  The optical frequency domain reflectometry technology is applied in the monitoring of dislocation of tunnel segments in the laboratory. Two original calculation methods are proposed to quantify the deformation between adjacent tunnel segments, and to quantitatively monitor the displacement of shield tunnel segments under load. A discrete element model is developed, and two kinds of deformation processes are simulated using an innovative high-performance discrete element software, MatDEM, developed by our group.

• Microbial loading and self-healing in cementitious materials: A review of immobilisation techniques and materials
  Mohamed, A. et al
  Materials & Design, Vol 245, Art No. 113249 (Sep 2024)
  Concrete has been a material of choice when it comes to building materials for decades. However, concrete has a number of challenges in which a major challenge being microcracking leading to excess damage and wastes. The development and advancement of self-healing technology throughout the past decade have seen the popular use of immobilization as a way of protecting bacteria from the harsh environments found in cementitious materials. This paper reviews the materials used for immobilization, categorising into organic materials and inorganic materials, and investigates the various immobilization techniques used to immobilize bacteria into polymeric structures and porous materials. The study evaluates the key findings in literature surrounding immobilization materials and methods as well as highlighting possible alternative sustainable materials and methods including waste/by-product resources. It was found that inorganic materials were superior to organic material in terms of self-healing and mechanical properties, with nanomaterials producing the highest crack closure of 1.20 mm. Various immobilization techniques efficiency was tested comparing microencapsulation, vacuum impregnation and adsorption methods. Further studies are needed to understand the relationship between carrier materials and cementitious matrix and explore the possible use of nanomaterials as a way of uniformly distributing bacteria in cementitious matrix.

• Comparative analysis of ternary blended cement with clay and engineering brick aggregate for high-performance 3D printin
  Chougan, M. et al
  Developments in the Built Environment, Vol 20, Art No. 100529 (Dec 2024)
  Utilising recycled brick aggregate in cementitious mixtures can decrease the overdependency on limited natural resources and improve the sustainability of concrete. This paper presents a potential solution to lower the amount of waste being landfilled and increase the sustainability of 3D concrete printing technology by combining low-carbon ternary blended cement with recycled aggregates. Hence, the effect of incorporating two types of recycled brick aggregate- clay brick (CBA) and engineering brick (EBA) on the properties of 3D printable ternary blended cement were investigated. The natural aggregate in a pre-existing 3D printable blend was substituted by up to 50 wt.-% with two varieties of recycled brick aggregates available throughout Europe. The recycled brick aggregates underwent characterisation to determine their properties. The fresh property evaluation using the green strength test was used to assess the effect of aggregate replacements on the mixture's shape stability. The mechanical performance of mixtures containing CBA and EBA, both cast and 3D printable mixes, was evaluated and compared to that of the control sample. The results indicated that incorporating recycled brick aggregate enhances green strength and Young's modulus significantly. Mechanical strength performance showed significant enhancement when incorporating RBA, which reached up to 67% and 55% for both cast and 3D printing methods, respectively. The suitability of the developed mix formulations for 3D printing was assessed by printing cylindrical objects.