• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2004.11a
• /
• pp.435-440
• /
• 2004

In this paper, the tension of assembly stay cable connected with massive anchorage block was calculated through back analysis of in-situ frequencies measured from a stadium structure. Direct approach to back analysis is adopted using the univariate method among the direct search methods as an optimization technique. The univariate method can search the optimal tension without regard to the initial ones and has a rapid convergence rate. To verify the reliability of back analysis, Tension formulas proposed by Zui et al. and Shimada were used. Tensions estimated by three methods are compared with the design tension, and are in a reasonable agreement with an error of more or less than 15%. Therefore, it is shown that back analysis applied in this paper is appropriate for estimation of cable tension force.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.7-14
• /
• 2003

In the back analysis of braced excavation based on displacement measurements, the accumulated errors of abnormal displacement caused by unexpected loads are usually observed. To minimize such errors, in this study, displacement increment was used fur back analysis rather than displacement for the conventional method. That is, the increment of sequential displacement is used as the objective function and the back analysis program is developed by taking advantage of sequential linear programming method by modified method of feasible directions. Based on small scale model test, the analysis of proposed method is verified.

• Tunnel and Underground Space
• /
• v.5 no.3
• /
• pp.205-213
• /
• 1995

In order to construct underground structural systems safely and economically, exact identification of the system parameters and accurate analysis of the system behaviors are required. Therefore, necessity of back analysis which is able to identify material properties of underground structural systems is increased. In this study a back analysis program which can identify the system parameters is developed using the direct method to be combined with the forward analysis program. Results of the back analysis program show good agreement with that of Gens et al. Sensitivity of the accuracy and convergency of the back analysis program on the number of measuring points is investigated. Comparison between the results of the back analysis with measurement data and the obtained material properties from the field tests shows good agreement for the real construction site.

• Tunnel and Underground Space
• /
• v.8 no.1
• /
• pp.46-52
• /
• 1998

The author conducted new back analysis method using monitoring data to a landslide which occurred around portal. In this case, because the tunnel being located under the sliding plane of the landslide, calculated value from the ordinary back analysis in which considered only stress release by the tunnel excavation didn't fit the measured value. Then, in the new method, a body force as the movement of the landslide mass was added to the ordinary back analysis and good results were obtained. Furthermore, the author carried out stability analysis of the landslide with the data of the back analysis and examined the loosened area and decreasing og the sliding plane strength due to the tunnel excavation.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.147-179
• /
• 2002

The important role of observational method in geotechnical engineering are emphasized together with the direction of future development, concerning successful application of the technique on the site investigation, design and feed back at various construction stages. Case histories on the application of feed back are introduced in order to achieve the most economical and reliable construction for tunnel, rock slope and deep excavations through feed back system at design and construction stages. Also the limitations and advantages of the observational method and the role of feed back system are discussed for construction of tunnel, rock slope and deep excavation in hard ground such as layered ground conditions including weathered, soft and hard rocks.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.11a
• /
• pp.479-484
• /
• 2000

The reliable estimation of the system parameters and the accurate prediction of the system behavior are important to design tunnel safely and economically. Therefore, the back analysis using the field measurements data is useful to evaluate the geotechnical parameter for tunnel. In the back analysis method, the selection of initial value and uncertainty of field measurements influence significantly on the analysis result. In this paper, to overcome uncertainty of field measurements, we performed the back analysis using the displacement data gained at each step of excavation and support.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.10a
• /
• pp.65-84
• /
• 2002

The Observational Method proposed by Terzaghi can be applied for the safe and economic construction projects where the exact prediction of the behavior of the structures is difficult as in the underground excavation. The method consists of measuring lateral displacement, ground settlement and axial force of supports in the earlier stage of the construction and back analysis technique to find the best fit design parameters such as earth pressure coefficient, subgrade reaction etc, which will minimize the gap between calculated displacement and measured displacement. With the results, more reliable prediction of the later stage can be obtained. In this study, back analysis programs using the Direct Method, based on the Hill Climbing Method were made and evaluated, and to overcome the limits of the method, Genetic Algorithm(GA) was applied and tested for the actual construction cases.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.9
• /
• pp.93-100
• /
• 2009

A core procedure of the direct search method used in this study is optimizing a difference between objective function and real displacement and correcting unknown variables. Because the research procedure comes from back-analyzing of the unknown variable of each layer, back-analyzing results need an additional optimization to minimize interferential effects of unknown variables. Therefore, the direct search method Is used to obtain optimized solutions without a partial differentiation of an objective function. The object of this research is developing the back analysis technique for multi-unknown variables by modeling the soil including underground structure Into upper and lower layer. In order to minimize interferent errors, repeated back analysis is performed and applicability on the real tunnel is examined. Consequently, the multi-layer analysis model is more precise in describing the real behavior of underground structure. It shows the validity of back analysis far multi-layer model which is the understructure placed on multi-layer boundaries.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.15 no.3
• /
• pp.357-373
• /
• 2013

In this paper, a back analysis program for analyzing the behavior of tunnel-ground system and evaluating the material properties and tunnel design parameters was developed. This program was designed to be able to implement the back analysis of underground structure by combination of using FLAC and optimized algorithm as direct method. In particular, Rosenbrock method which is able to do direct search without obtaining differential coefficient was adopted for the back analysis algorithm among optimization methods. This back analysis program was applied to the site to evaluate the design parameters. The back analysis was carried out using field measurement results from 5 sites. In the course of back analysis, nonlinear regression analysis was carried out to identify the optimum function of the measured ground displacement. Exponential function and fractional function were used for the regression analysis and total displacement calculated by optimum function was used as the back analysis input data. As a result, displacement recalculated through the back analysis using measured displacement of the structure showed 4.5% of error factor comparing to the measured data. Hence, the program developed in this study proved to be effectively applicable to tunnel analysis.

• 제어로봇시스템학회:학술대회논문집
• /
• 2000.10a
• /
• pp.456-456
• /
• 2000

The back projection histogram method has been proposed as the method to construct an image from waves reflected from a buried object for subsurface radar. This method is compose of two phases, i.e., a back projection image construction process and a back projection image superposition process. A simulation analysis of this method has been studied. In this paper, an experimental study is demonstrated in air as the homogeneous Held using three cylinders as buried objects.