Advance prediction method for rock mass stability of tunnel boring based on deep neural network of time series

Geological layers excavated using tunnel boring machines are buried deeply and sampled difficultly, and the geological behavior exhibits high diversity and complexity. Excavating in uncertain geology conditions bears the risks of excessive damage to the equipment and facing geologic hazards. Many scholars have used various signals to predict the advance geology conditions, but accurate prediction of these conditions in real-time and without effecting operations has not been realized yet. In this article, based on a large amount of corresponding data, an advance prediction model of the rock mass category (RMC) is formulated. First, the problem is divided into two parts, which are modeled separately to reduce the complexity of design and training. Then, the two models are combined in a pre-trained model, which is retrained to as the final prediction model to avoid the problem of error accumulation. The final model can predict the advance RMC in real-time and without affecting operations. The accuracy of the prediction model reaches 99% at an advance time of 60 min. The advance RMC can be used to guide the selection of support modes and control parameters without additional detection equipment and excavation down-time.

Assessment of rate of penetration of a tunnel boring machine in the longest railway tunnel of Turkey

One of the most important issues in tunnels to be constructed with tunnel boring machines (TBMs) is to predict the excavation time. Excavation time directly affects tunnel costs and feasibility. For this reason, studies on the prediction of TBM performance have always been interesting for tunnel engineers. Therefore, the purpose of the study is to develop models to predict the rate of penetration (ROP) of TBMs. In accordance with the purpose of the study, a new database including 5334 cases is obtained from the longest railway tunnel of Turkey. Each case includes uniaxial compressive strength, Cerchar Abrasivity Index, α angle, weathering degree and water conditions as input or independent variables. Two multiple regression models and two ANN models are developed in the study. The performances of the ANN models are considerably better than those of the multiple regression equations. Before deep tunnel construction in a metamorphic rock medium, the ANN models developed in the study are reliable and can be used. In contrast, the performances of the multiple regression equations are promising, but they predict lower ROP values than the measured ROP values. Consequently, the prediction models for ROP are open to development depending on the new data and new prediction algorithms.

A simulation-based decision support tool for integrating site layout and construction planning of tunneling projects

Purpose Integrating construction and site layout planning in mechanized tunnel infrastructure projects is essential due to the mutual impacts of construction planning and site layout decisions. Simulation can incorporate site layout planning and construction planning of tunneling projects in a unified environment. However, simulation adoption by industry practitioners has remained relatively limited due to the special skills required for building and using simulation models. Therefore, this paper aims to create a simple-to-use simulation tool that supports site layout and construction operation planning of tunneling projects. This tool intends to promote the simulation application in site layout planning. Design/methodology/approach The current paper proposes simulation as a decision support tool (DST) to provide an integrated environment for modeling tunnel construction operations, site layout and capturing the mutual impacts. A special purpose simulation (SPS) tool was customized and developed for typical mechanized tunneling projects, by tunnel boring machines, to facilitate building the model and allow access to users with limited simulation knowledge. Findings The results show that the developed SPS tool is of great assistance to construction industry practitioners to analyze a variety of site layout and construction plan scenarios and make informed decisions based on its comprehensive and intuitive outputs. Originality/value The main contribution of this research is to promote simulation application in site layout planning of tunneling projects through the development of a simple-to-use tool, which has sufficient details for site layout planning and constraints. The developed DST enables planners to make decisions simultaneously on the site layout, other construction planning variables and identify the most efficient plan.

Geological forward-prospecting using Tunnel-seismic-while-drilling (TSWD) method: A case study of the water supply project at Songhua River, China

Unexpected geological heterogeneities in the tunnel lines often cause safety issues and economic losses during excavation using Tunnel Boring Machines (TBMs). Therefore, collecting geological information ahead of the excavation front is important to prevent geological disasters and ensure excavation safety. To predict the geological conditions ahead of the TBM-excavated tunnel in the water supply project at the Songhua River in China, the tunnel-seismic-while-drilling (TSWD) method was adjusted and then applied. First, common source gather (CSG) data were acquired to record TBM drilling noise (pilot signal and seismic waves); a processing approach (including normalization, cross-correlation, wave-field separation, and migration) was used to image the major relevant geological heterogeneities ahead of the excavation front. A synthetic study from a numerical model with a fault verified the feasibility of the modified TSWD method to identify and image geological interfaces. Then this method was applied to field data resulting from a TBM tunnel excavation project. The field test of the modified TSWD in the TBM tunnel revealed the fractured zones, fault boundaries, and a pre-excavated tunnel ahead, providing the required geological information for TBM tunneling and preventing geologically caused safety issues.

A perspective of pipejacking works by tunnel boring machines in Hong Kong: part II – applications, problems encountered, cost and prospects

In this paper, application of special techniques such as pipe roof construction, retractable TBM, and rectangular TBM to address site difficulties and constraints is highlighted. Cost and prospects of TBM pipejacking works are discussed. Some observations, including problems encountered and overcome, are also highlighted. This paper should be read together with part I, which covers development, selection of design, operations and types of techniques.

A perspective of pipejacking works by tunnel boring machines in Hong Kong: part I – development, selection of design, operations and types of techniques

In this paper, the history of pipejacking works by tunnel boring machines in Hong Kong, their development, selection of design method and tunnel boring machine (TBM), operations, length and alignment of a pipeline, types of techniques to suit different site constraints and ground conditions, and performance of the works are discussed. This paper should be read together with part II, which covers applications, problems encountered, cost and prospects.