Christian Moormann

TBM performance estimation using a classification and regression tree (CART) technique

With widespread increasing applications of mechanized tunneling in almost all ground conditions, prediction of tunnel boring machine (TBM) performance is required for time planning, cost control and choice of excavation method in order to make tunneling economical. Penetration rate is a principal measure of full-face TBM performance and is used to evaluate the feasibility of the machine and predict the advance rate of an excavation. In this study, a database of actual machine performance from T05 and T06 tunnels of the deep tunnel sewerage system (DTSS) project in Singapore which include: rock mass uniaxial compressive strength, brittleness index (Bi), volumetric joint account (Jv), joint orientation (Jo), TBM specifications and corresponding TBM performance has been compiled. Then, for prediction of specific rock mass boreability index (SRMBI), two different models including classification and regression tree (CART) analysis and multivariate regression analysis (MVRA) have been developed. As statistical indices, correlation coefficient (R2), root mean square error (RMSE) and variance accounted for (VAF) were used to evaluate the efficiency of the developed models for determining the SRMBI of TBMs. According to the obtained results, it was observed that the performance of the CART model is better than the MVRA.

Examining Feasibility of Developing a Rock Mass Classification for Hard Rock TBM Application Using Non-linear Regression, Regression Tree and Generic Programming

Geotechnical and geological parameters have the greatest impact on the performance of hard rock tunnel boring machines (TBMs). This includes the rock and rock mass properties that affect the rate of penetration (ROP) as well as the machine utilization that is heavily dependent on ground support type and related machine downtime and delays. However, despite the widespread use of TBMs and established track records, accurate estimation of machine performance is still a challenge, especially in complex geological conditions. The past studies have tried to use rock mass classification systems for improving the accuracy of the machine performance prediction. Rock mass classifications has been primarily developed for design of ground support, and as such, have not offered a good fit for estimation of TBM performance. This paper will review performance of a hard rock TBM in a 12.24xa0km long tunnel and offers analysis of field performance data to evaluate the relationship between various lithological units and TBM operation. The results of statistical analysis of the initial 5.83xa0km long tunnel indicate strong relationships between geomechanical parameters and TBM performance parameters. Site specific models, including Non-linear regression analysis (NLRA), Classification and regression tree (CART), and Genetic Programming (GP) have been used for analysis of a TBM performance relative to the ground condition data. The current study has looked at the possibility of developing a new rock mass classification system for TBM application by using the above noted analysis. Preliminary results indicate that CART can be used for offering a proper rating scheme for a rock mass classification system that can be used for TBM applications.

Numerical Simulation of Open Ended Pile Installation in Saturated Sand

Open-ended pipe piles have been the preferred choice for various foundation applications, and in particularly for offshore wind turbines. The need to know, well in advance, certain design parameters prior to installation thus arises, and through numerical analyses, ranges for these installation parameters, and the behavior of the sand surrounding the pile can be estimated. Offshore environment poses an additional challenge of taking into account not only the penetration process and effects of dynamic loading of the sand, but also the pore pressure built up in the soil skeleton. This paper presents a novel approach to simulate the dynamic installation process of open-ended piles in saturated soil. Thus, the simulation also provides the basis to predict the pile behavior due to axial or lateral loading considering the installation effects. By coupling the aspects of Lagrangian and Eulerian methods, a particle-based method, called Material Point Method (MPM), more specifically its extension called Convected Particle Domain Interpolation (CPDI) method has been employed in the present work. To simulate saturated media, an extension of CPDI is incorporated in the form of 2-phase formulation, different velocities for soil and water are considered and thus able to capture precisely the saturated-soil behavior. A 2-D axisymmetric model is considered, along with a penalty method formulation to calculate contact forces between pile and soil. This method, when applied in conjunction with the hypoplastic constitutive model, provides a framework which allows us to study detailed effects of pile installation on the surrounding soil.

Deep Excavations with special ground shape

The extension of our infrastructure in urban areas and also in rural embossed areas is often linked with the design and construction of complex geotechnical structures. Especially the design of the temporarily required excavation structures with the plurality of construction phases and the varying deformation states and stress situations has to be mentioned. In the most cases the examination of the bearing and deformation behavior in plain strain models is preferred to the detailed threedimensional investigation of the soil-structure interaction. In reality deep excavations are spatial systems significantly influenced by the geometric and geotechnical boundary conditions [Chiou et. al. (1993)]. The three-dimensional soil-structure interaction and the influence on the bearing and deformation behavior of nearly rectangular excavations in cohesive soils are investigated by the analysis of several field measurements and the execution of a parametric study. The stiffening effect of the corners and its influence on the bearing behavior of the structure is apparent and leads to a more realistic and more economic design. The realistic approach of the acting earth pressure is contrary to the approach formulated in the technical guidelines, e.g. EAB (2012). Further investigations of the bearing and deformation behavior of deep excavations with special ground shape under consideration of the geotechnical and the structural boundary conditions shall lead to more realistic design approaches. CASE STUDY: RIVER POWER PLANT IFFEZHEIM, GERMANY