An Identification Method of Geological Boundary Using Elastic Waves
This paper focuses on a technique for identifying the geological boundary of the ground strata in front of a tunnel excavation site using the first order adjoint method based on the optimal control theory. The geological boundary is defined as the boundary which is different layers of elastic modulus. At tunnel excavations, it is important to presume the ground situation ahead of the cutting face beforehand. Excavating into weak strata or fault fracture zones may cause extension of the construction work and human suffering. A theory for determining the geological boundary of the ground in a numerical manner is investigated, employing excavating blasts and its vibration waves as the observation references. According to the optimal control theory, the performance function described by the square sum of the residuals between computed and observed velocities is minimized. The boundary layer is determined by minimizing the performance function. The elastic analysis governed by the Navier equation is carried out, assuming the ground as an elastic body with linear viscous damping. To identify the boundary, the gradient of the performance function with respect to the geological boundary can be calculated using the adjoint equation. The weighed gradient method is effectively applied to the minimization algorithm. To solve the governing and adjoint equations, the Galerkin finite element method and the average acceleration method are employed for the spatial and temporal discretizations, respectively. Based on the method presented in this paper, the different boundary of three strata can be identified. For the numerical studies, the Suemune tunnel excavation site is employed. At first, the blasting force is identified in order to perform the accuracy improvement of analysis. We identify the geological boundary after the estimation of blasting force. With this identification procedure, the numerical analysis results which almost correspond with the observation data were provided.
Keywords: Finite Element Method, parameter identification, optimal control theory, average acceleration method, first order adjoint equation method, weighted gradient method, geological boundary, navier equation
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1332318Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1277
 B.M.Chaparro, S.Thuillier, L.F.Menezes, P.Y.Manach and J.V.Fernandes : "Material parameters identification: Gradient-based, genetic and hybrid optimization algorithms", J. Comput. Mat. Sci., Vol.44, No.2, pp.339-346, 2008.
 F.X.Le Dimet, I.M.Navon and D.N.Daescu : "Second Order Information in Data Assimilation", Month. Weath. Rev., Vol.130:3, pp.629-648, 2002.
 F.Yoshida, M.Urabe, V.V.Toropov : "Identification of Material Parameters in Constitutive Model for Sheet Metals from Cyclic Bending Tests", Int. J. Mech. Sci., Vol.40, pp.237-249, 1998.
 G.Swoboda, Y.Ichikawa, Q.Dong and M.Zaki : "Back Analysis of Large Geotechnical Models", Int. J. Numer. Analy. Meth. Geomech., John Wiley and Sons Ltd., Vol.23, No.13, pp.1455-1472, 1999.
 G.Wu : "Dynamic response analysis of saturated granular soils to blast loads using a single phase model", AGRA Earth and Environmental Ltd., Burnaby, 1995.
 K.Kojima, T.Kodama and N.Kaneko : "Parameter Identification and Control of Ground Temperature", Int. J. Comput. Fl. Dyn., Vol.7, pp.193-200, 1996.
 M.Kawahara, K.I.Sasaki and Y.Sano : "Parameter Identification and Optimal Control of Ground Temperature", Int. J. Numer. Meth. Fl. Vol.20, pp.789-801, 1995.
 M.Piasecki and N.D.Katopodes : "Dispersion Parameter Estimation in Free Surface Flow Region", J. Hyd. Engrg., ASCE, Vol.125, No.7, pp.714-724, 1999.
 M.Sezaki, ┬¿O.Aydan, Y.Ichikawa and T.Kawamoto : "Properties for Initial Design of Tunnels by NATM Using Rock Mass Data-Base System", Japan Society of Civil Engineers Magazine, No.421/VI-13, pp.125-134, 1990.
 N.Koizumi and M.Kawahara : "Parameter Identification Method for Determination of Elastic Modulus of Rock Based on Adjoint Equation and Blasting Wave Measurements", Int. J. Numer. Analy. Meth. Geomech., 2008. (In press)
 R.Mahnken, E.Stein : "Parameter Identification for Viscoplastic Models Based on Analytical Derivatives of a Least-Squares Functional and Stability Investigations", Int. J. Plasticity, Vol.12, No.4, pp.451-479, 1996.
 R.Mahnken, E.Kuhl : "Parameter Identification of Gradient Enhanced Damage Models with the Finite Element Method", Eur. J. Mech., A/Solids, Vol.18, pp.819-835, 1999.
 T.Asai and M.Kawahara : "Parameter Identification of Soil Seepage Interraction Problem Using Finite Element Method", Bulletin of the Faculty of Science and Engineering, Chou Univ. Vol.41, pp.15-31, 1998.
 T.Ohkami and G.Swoboda : "Parameter Identification of Viscoelastic Materials", J. Comput. Geotech., Elsevier Science Ltd., Vol.24, No.4, pp.279-295, 1999.
 U.S.Army Corps of Engineers : "Systematic Drilling and Blasting for Surface Excavations", Engineering Manuals, EM 1110-2-3800, Office of the chief, U. S. Army Corps of Engineers, Washington, D.C., 1972.
 Y.Huang and Z.Liu : "Time Domain Parameters Identification of Foundation-structure Interaction System", J. Appl. Math. Mech., Vol.26, No.7, pp.855-864, 2005.
 Y.Takahashi and M.Kawahara : "Identification of Reynolds Number Using Automatic Differentiation", Inverse Problems, Design and Optimization Symposium, Rio de Janeiro, Brazil, 2004.
 Z.Xiang, G.Swoboda and Z.Cen : "Optimal Layout of Displacement Measurements for Parameter Identification Process in Geomechanics", Int. J. Geomech., Vol.3, No.2, pp.205-216, 2003.