EN
EN
**Behro Comprehensive Consulting Engineers**
**Dariush Mohammadi, Kourosh Shahriyar, Parviz Maarefvand, Ebrahim Farrokh**
Geotechnical Engineering (ice publishing)
**June 6, 2023**
The design of **cutterhead openings** in **Earth Pressure Balance Machines (EPBMs)** is a critical factor in tunnelling performance in soft ground. Although TBM manufacturers have developed different opening-distribution patterns based on their practical experience, the body of published technical literature on this subject remains very limited. To address this knowledge gap, this article first reviews the results of **field studies on the performance of cutterhead openings in soft ground** and then focuses on **numerical modelling based on the Discrete Element Method (DEM)** to evaluate the behavior of the EPB system and the **flowability of cohesive and non-cohesive soils** under different cutterhead opening patterns.
In the numerical phase of the study, different **cutterhead opening-distribution patterns** were investigated, and their effects on key operational parameters, including **thrust force, cutterhead torque, and soil flowability**, were analyzed. The results show that, for **cohesive soils**, increasing the opening ratio in the central region of the cutterhead plays a critical role in reducing the likelihood of **clogging**, improving soil flow, and reducing both **thrust force and torque**. Based on the **DEM modelling**, the optimum opening ratio and its distribution for different soil types were proposed. The **fluid-like behavior of particles within the EPB chamber** was also investigated through analysis of the **soil velocity field**.
The findings of the study indicate that a **central opening ratio exceeding 50%** is essential for cohesive soils. This approach can reduce **thrust force and cutterhead torque by approximately 34%** while significantly improving soil flow conditions. It is also recommended that the openings in the central region of the cutterhead be distributed according to the proposed pattern (as shown in the article’s design diagram) to improve the **mechanical, hydraulic, and electrical performance** of the machine. Alongside the investigation of a **real-world case study**, these findings can provide practical guidance for the **TBM industry** in designing next-generation cutterheads for different geological conditions.
