Search Results (3)

In this paper, a theoretical estimation model of TBM thrust, torque, and power in the rock–soil interface (RSI) of mixed ground is developed, including a new force model for the drag cutter that accounts for chamber pressure and soil friction. A distribution model of the disc cutters and drag cutters on the cutterhead adaptable to different excavation surfaces is built in order to visualize the cutting process as the TBM cutterhead rotates, and a program is created and that runs smoothly using the Python version 3.8, which can recognize the numbers and calculate the forces of the disc cutters and drag cutters in the soft and hard strata, respectively. Then, combining with friction forces and chamber pressure calculated by the program, the variation in torque, thrust, and power are produced. Subsequently, a new index (MPPI), which considers both the thrust of the TBM and cutterhead torque, for forecasting TBM tunneling performance in composite strata is presented. The reliability of the index as well as the estimation model are validated using data from an actual project to offer recommendations for future tunneling projects. Full article

The Cutter Soil Mixing (CSM) method, a relatively recent innovation, employs twin-wheel milling and profound agitating machinery for wall construction. In an endeavor to scrutinize the displacements and internal support stresses to the support structure during the excavation of a multi-span foundation pit founded upon the CSM method, a two-dimensional finite element model was established, utilizing the Midas GTS NX 2019 V1.2 finite element software. This model was grounded on a multi-span foundation pit excavation endeavor situated in the eastern expanse of China, where steel bracing and the CSM method assumed the preeminent mantle of support. A comprehensive scrutiny encompassed ten distinct working conditions, each juxtaposed and dissected to ascertain the displacements affecting the CSM wall and the forces exerted upon the support system during the foundation excavation process. The research findings manifest a certain interplay between the embedment depth of the CSM wall and the span of the pit excavation in shaping the displacement and support stresses within the supporting structure. While deeper embedment augments the potential for enhanced support outcomes, its efficacy remains constrained. As the embedment depth increases, the internal support moment and lateral displacement of the wall increase slightly. Taking a pit with a shallow embedded CSM wall as an example, wherein both the lateral and vertical displacements experience an ascent followed by a descent, culminating at the juncture of a four-span pit. Likewise, the axial force and bending moment exerted upon the steel supports undergo a similar trajectory, culminating with a two-span pit as the threshold. At the five-span, the maximum lateral displacement of the CSM wall exceeds that observed at the two-span by an increment of 21.14%. These findings offer invaluable insights into the embedment depth of diaphragm walls and the span of pit excavations, wielding profound implications for future undertakings akin to the foundation pits in question. Full article

Aiming at the problems of low uniformity and utilization rate in the traditional deep application method of orchard manure, a soil–fertilizer collision mixing and mulching device was designed. The ditching mechanism, the structure of the soil divider, and the fertilizer delivery auger were analyzed and designed. Furthermore, with the rotational speed of the cutter and auger and the deflection angle of the soil divider as factors, as well as the uniformity of soil–fertilizer mixing and mulching as evaluation indexes, the discrete element simulation tests were conducted. The simulation results showed that when the turret speed, the stirrer speed and the soil separator deflection angle were 140 r/min, 146 r/min and 22°, the mixing uniformity and mulching uniformity were the highest, which was 88.35% and 96.86%, respectively. Based on the optimal parameters, the field test was conducted, and the soil–fertilizer mixing uniformity was 87.02%, with a relative error of 1.33% compared with the simulation test results. The relative error of 94.37% of mulch uniformity is 2.49%, which indicates that the simulation optimization results are reliable and the mixing performance of the device is good and can meet the requirements of soil–fertilizer mixing operation. The results of this study can provide an important reference for the design of the soil and fertilizer mixing machine. Full article