In order to study the gas permeation characteristics of municipal solid waste (MSW), a set of test equipment is independently developed. The experimental equipment measures MSW's gas permeability, porosity, and gas preferential flow parameters. The composition and operation method of the equipment are introduced. Moreover, the self-developed equipment carries out laboratory tests on gas permeation of MSW under the influence factors of initial pressure and moisture content. Test application results show that the equipment can realize all pre-designed functions. The experimental results showed that the peak value of the gas breakthrough curve increased gradually with the increase of initial pressure and increased with the growth of moisture content. When the moisture content is 54.6%, 70.6%, and 86.6% as the initial pressure is 0.05 MPa, the gas permeability of MSW is 1.096x10(-12) m(2), 0.937x10(-12) m(2), and 0.787x10(-12) m(2), respectively, and the porosity is 0.573, 0.501, and 0.358, respectively. When the initial pressure of 0.02 MPa, 0.05 MPa, and 0.1 MPa as the moisture content is 54.6%, the peak value of gas flow rate at the outlet of MSW is 0.006 L/s, 0.012 L/s, and 0.02 L/s, respectively, and the time of gas passing through the sample is 47s, 58s, and 65s, respectively. The research results enrich the experimental equipment for studying the gas permeation characteristics of MSW and provide data support for the subsequent research on the migration model of landfill gas.
Landfill materials composed of weak soil are closely related to stability problems. To minimise this problem, various stabilisation techniques are often used, one of which is the addition of polyacrylamide anionic polymer (APAM). In this paper, soil behaviour before and after adding APAM in the West Bandung area, Indonesia, has been analysed. It has been done with different variables by considering the landfill's geometry and the soil material's properties. Several models were analysed to determine the slope height and angle that are safe for soil stabilisation. The modelling was done using the finite element method based on the soil hardening criteria model and Mohr-Coulomb. The analysis results show that with the increase in height and slope, the safety factor (FS) decreases, and the deformation increases. Conversely, if the height and slope decrease, the FS increases, and the deformation decreases. It is observed that the soil with the highest percentage of APAM (1%) has produced the highest shear strength parameters and the lowest deformation. This study found that weak soil treated with APAM can be used as a backfill material, but the potential for collapse is more significant.
Cement stabilization is a go-to technique for improving the engineering characteristics of marine clays. As per the previous studies, numerous factors influence the effectiveness of cement stabilization. It is well established that the cement content, molding water, and curing periods are the major controlling factors. Due to the complex dynamics among such factors, there is a critical need to understand the interplay between these factors to achieve optimal performance in cement stabilization of marine clays. The paper adopts an analytical approach to quantify the impact of controlling factors using unconfined compressive strength (UCS) data. Design Expert 13 was employed for the experimental design and the response surface study. A central composite design (CCD) was adopted for the analysis, and the ranges of factors were fixed in accordance with the previous studies and the respective optimum moisture conditions. The ranges of cement content (CC), molding water content (MWC), and curing days (CD) were fixed as 5 to 15%,15 to 21%, and 0 to 14 days, respectively. The statistical analysis using ANOVA was used to arrive at a statistically significant quadratic model. A quadratic equation was generated depicting each factor's individual and interactive influence on the unconfined compressive strength of the cement-stabilized marine clay. The optimization results showed a maximum unconfined compressive strength value of 487.49 kPa for a cement content of 15%, curing days-14 days, and a molding water content of 19.67%. The study aids in understanding the extent of influence of binder content, molding, and curing conditions on the performance of cement-stabilized marine clay.
Tunneling projects encounter challenges in predicting Rate of Penetration (ROP), often leading to cost overruns. This study introduces a deep learning approach, combining Deep Feed Forward (DFF) and Long-Short Term Memory (LSTM) techniques to enhance the accuracy of ROP prediction. Focused on the Mae Tang- Mae Ngad Project and its geological complexities in massive and highly fractured granite rock conditions, the research aims to improve ROP predictions. The study demonstrates substantial improvements, revealing Root Mean Square Error (RMSE) values of 0.162 (m/h) for DFF and 0.216 (m/h) for LSTM. Notably, the models exhibit enhanced performance in massive rock conditions with an RMSE of 0.110 (m/h), while highly fractured granite shows an RMSE of 0.261 (m/h). These findings underscore the potential for more precise predictions, addressing historical inaccuracies that often lead to cost overruns ranging between 50 and 900 percent. Integrating deep learning techniques proves valuable, offering a pathway for more reliable and cost-effective tunnel construction endeavors.
This paper presents a comparative analysis between simplified and Finite Element Method (FEM) approaches for evaluating seismic forces in circular tunnels, with a specific focus on the Algiers Metro as a practical case study, considering the Boumerdes earthquake in 2003. The FE modeling was carried out under plane strain conditions, using the contraction method to phase the performed model and incorporating the Volume Loss coefficient (VL). The behavior of soil and tunnel elements was considered linear elastic. Based on the maximum strain rate of the soil medium, various simplified approaches existing in the literature were adopted in this study, including solutions proposed by Wang (1993), Penzien (2000), Bobet (2003, 2010), and Park et al. (2009). The maximum shear strain rate was determined by plotting the cumulative horizontal displacement of the soil profile and then using this value to deduce the vertical strain rate. Results indicate that increasing VL values initially reduce axial thrust, followed by an increase. Shear force and bending moment proportionally increased with the VL ratio, remaining within the practical range of simplified solutions. The best agreement between the simplified and FEM approaches was observed when VL ranged between 1 and 2. Additionally, the total principal stresses around the tunnel increased with the VL ratio. This study highlights the importance of estimating the appropriate maximum strain rate and VL ratio to achieve accurate results while using both simplified and FEM approaches.
