of a tunnel digging machine Paolo Boscariol DTG University of Padova Vicenza, VI 36100, Italy Alessandro Gasparetto DPIA University of Udine Udine, UD 33100, Italy Lorenzo Scalera DPIA University of Udine Udine, UD 33100, Italy Renato Vidoni Faculty of Science and Technology Free University of Bozen-Bolzano Bolzano, BZ 39100, Italy In this work the kinematics of a large size tunnel digging ma- chine is investigated. The closed-loop mechanism is made by 13 links and 13 class 1 couplings, 7 of which are actuated. This kind of machines are commonly used to perform ground drilling for the placement of reinforcement elements during the construction of tunnels. The direct kinematic solution the numerical solution of the closure equation written using the Denavit-Hartenberg convention, while the third is based lent spherical mechanism. The procedures have been tested and implemented with reference to a real commercial tunnel digging machine. The use of the proposed method for the a major reduction of the computation time in comparison with the standard numerical solution of the closure equation. 1 Introduction Underground tunnels are excavated using mainly two nel boring machines [1], the other, of more frequent appli- cation, is the use of common digging techniques with the paolo.boscariol@unipd.it use of mechanical excavators and explosives [2]. The ex- cavation resulting form tunnel boring can represent a major problem for the stability of the nearby soil strata and geo- logical structures. The resulting soil displacements must be minimized in order to avoid the possible damage to existing structures, especially in urban areas, where tunnels excava- tions are usually performed at shallow depths. For this rea- son the physical properties of the medium to be excavated often requires to perform a reinforcement over the crown of pressure injection of concrete, often called jet grouting [4]. This method is particularly popular in Europe, where weak soil structures are reinforced by means of the installation of partially overlapping cylinders of concrete. The idea is to enforce and stabilize the ground material through a support structure ahead and around the excavation. This technique reinforces the work area by creating a supporting system as a reinforced arched shell and allows a fast and safe excavation. Sub-horizontal jet grouting, spiling and pipe roof are other common pre-consolidation methodologies [5]. The jet grouting method improves the strength, stiffness and permeability characteristics of weak soils (e.g. sandy, gravel formations) through the injection of the grouting ma- terial, most often a cement-based grout, into boreholes of predetermined shape, size and depth performed on the face P. Boscariol, A. Gasparetto, L. Scalera, R. Vidoni, digging machine, Journal of Mechanism and Robotics, 9(3), pp. 1-13, 2017. Paper No: JMR-16-1040; doi: 10.1115/1.4035797 page 1 16