• International Journal of Highway Engineering
• /
• v.17 no.6
• /
• pp.27-32
• /
• 2015

PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.6
• /
• pp.183-193
• /
• 2003

Most construction works on the soft ground adopt instrumentation to manage settlement and stability of the embankment. The rapid progress of the information technologies and the digital data acquisition on the soft ground instrumentation has led to the fast-growing amount of data. Although valuable information about the behaviour of the soft ground may be hiding behind the data, most of the data are used restrictedly only for the management of settlement and stability. One of the critical issues on soft ground instrumentation is the long-term settlement prediction. Some observational settlement analysis methods are used for this purpose. But the reliability of the analysis results is remained in vague. The knowledge could be discovered from a large volume of experiences on the observational settlement analysis. In this article, we present a database to store settlement records and data mining procedure. A large volume of knowledge about observational settlement prediction were collected from the database by applying the filtering algorithm and knowledge discovery algorithm. Statistical analysis revealed that the reliability of observational settlement analysis depends on stay duration and estimated degree of consolidation.

• Geomechanics and Engineering
• /
• v.33 no.5
• /
• pp.463-475
• /
• 2023

Tunnel construction activity, conducted mainly in mountains and within urban centres, causes soil settlement, thus requiring the relevant management of slopes and structures as well as evaluations of risk and stability. Accordingly, in this study we performed a three-dimensional finite element analysis to examine the behaviour of piles and pile cap stability when a tunnel passes near the bottom of the foundation of a pile group connected by a pile cap. We examined the results via numerical analysis considering different conditions for reinforcement of the ground between the tunnel and the pile foundation. The numerical analysis assessed the angular distortion of the pile cap, pile settlement, axial force, shear stress, relative displacement, and volume loss due to tunnel excavation, and pile cap stability was evaluated based on Son and Cording's evaluation criterion for damage to adjacent structures. The pile located closest to the tunnel under the condition of no ground reinforcement exhibited pile head settlement approximately 70% greater than that of the pile located farthest from the tunnel under the condition of greatest ground reinforcement. Additionally, pile head settlement was greatest when the largest volume loss occurred, being approximately 18% greater than pile head settlement under the condition having the smallest volume loss. This paper closely examines the main factors influencing the behaviour of a pile group connected by a pile cap for three ground reinforcement conditions and presents an evaluation of pile cap stability.

• Architectural research
• /
• v.20 no.3
• /
• pp.65-73
• /
• 2018

The restoration of foundations supporting the immense load of the stone pagoda at Mireuksa Temple Site prioritizes securing its structural stability. But so far, rammed earth construction is still not easy to determine the structural stability. This paper aims to emphasize that a scientific experimental study was conducted on a rammed earth construction, to identify its methodology and obtain objective data about structural stability of the foundation work. An experimental study fabricated specimens from the soil that had been removed during the excavation survey, determined the allowable bearing capacity through plate load tests, and compared the results with the predicted stress after reassembly of the stone pagoda to estimate the structural stability. Then, the repair method was selected based on the experimental study result. The evaluation method of the restoration of foundations consisted of an examination of the allowable bearing capacity and settlement. The allowable bearing of the reinforced foundation was more than twice the contact pressure under the stacked stones of the pagoda. The possibility of settlement of the rammed earth foundation soil layer during the pagoda assembly is expected to be very low because the settlement amount of the reformed soil layer is less than half of the settlement of the stabilized existing soil layer.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.898-905
• /
• 2005

The settlement of embankment on soft clay includes shear settlement due to shear deformation. Even though the consolidation settlement is not related to lateral displacement, but shear settlement makes the embankment unstable because it deforms ground and decreases the ground strength. In order to determine the shear deformation behaviour during embankment construction, 3 cases (1B, 2B, and 3B) of rapid undrained loading tests on soft clays were performed. Shear settlement is consist of elastic settlement, plastic settlement and viscous settlement. Elastic settlement isn't considered because the range is small, therefore the first is the range of plastic displacement, and the second is that of viscous displacement in the displacement-time curve for each loading stage. After determining that the change in the inclination of the viscous displacement range is larger than in the plastic displacement range after the ground failure occurs for the loading stage, the stability management methods were suggested considering that it is hard to divide the plastic displacement range and the viscous displacement range. The stability management method was based on the ratio of the plastic displacement range's inclination and the viscous displacement range's inclination. A stability management method based on the ratio of the total inclination for each loading stage compared to the whole inclination in the initial loading stage was also recommended.

• Industry Promotion Research
• /
• v.8 no.2
• /
• pp.93-100
• /
• 2023

This study used Gangwon provincial social survey data(2021) to verify the effect of working environment satisfaction of the main working population on settlement consciousness and the mediating effect of subject employment stability. The working environment satisfaction was analyzed by dividing it into three sub-factors: income satisfaction, working conditions satisfaction, and community life satisfaction. As a result of the study, all three sub-factors of working environment satisfaction and subjective employment stability had a positive correlations with settlement consciousness. It was confirmed that subjective employment stability had a partial mediating effect when each of the three sub-factors of working environment satisfaction affected settlement consciousness. Based on the results of the study, it is meaningful to provide empirical data for preventing outflow of the local population by revealing the effect of working environment satisfaction and subjective employment stability on the settlement consciousness.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.796-804
• /
• 2008

Various design factors should be considered in order to apply the concrete slab track system on the soil/rock roadbed. One of the important factors is the settlement of roadbed. This settlement of concrete track should be supervised under the allowable settlement limit. If the settlement of roadbed under the concrete track exceed the allowable limit, the train serviceability will considerably come down and furthermore the fatal disaster may happen. Therefore, in this paper we introduced a digitalized grouting method as a settlement restoration method that can be suitably adopted to the concrete slab track. And we also evaluated the train service stability through the analysis of the track behavior according to the difference of the stiffness between the grouted part and the original roadbed.

• International Journal of Railway
• /
• v.6 no.2
• /
• pp.45-52
• /
• 2013

Railway construction needs vast soil investigation for its infrastructure foundation designs along the planned railway path to identify the design parameters for stability and serviceability checks. The soil investigation data are usually classified and grouped to decide design input parameters per each construction section and budget estimates. Deterministic design method which most civil engineer and practitioner are familiar with has a clear limitation in construction/maintenance budget control, and occasionally produced overdesigned or unsafe design problems. Instead of using a batch type analysis with predetermined input parameters, data population collected from site soil investigation and design load condition can be statistically estimated for the mean and variance to present the feature of data distribution and optimized with a best fitting probability function. Probabilistic approach using entire feature of design input data enables to predict the worst, best and most probable cases based on identified ranges of soil and load data, which will help railway designer select construction method to save the time and cost. This paper introduces two Monte Carlo simulations actually applied on estimation of retaining wall external stability and long term settlement of organic soil in soil investigation area for a recent high speed railway project.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.6 no.4 s.23
• /
• pp.7-14
• /
• 2006

The tilting-train being operated in pre-existing rail road has a different running mechanism compared to currently operated trains. Therefore, it needs to investigate the evaluation of the track performance, the stability of the tilting-train in operating condition, and the stability of the roadbed. In this study, when the tilting train is operated in the rail joint with the allowable velocity limited by the track performance and the stability of the tilting-train, the settlement of the roadbed has been evaluated by using numerical analysis. The loading on the ground surface generated by the operating tilting-train generates the settlement of the roadbed. The settlement induced by the tilting-train loading has been compared to the allowable settlement and the factor of safety defined by the ratio of the allowable settlement to the settlement generated by the applied loading is evaluated.

• Geotechnical Engineering
• /
• v.12 no.5
• /
• pp.41-54
• /
• 1996

In this paper, the consolidation settlement of the landfill foundation during and after the period of disposal is analyzed using the program CONSOL which can include the influence of waste load and the leachate level into the analysis. the stability analysis of the embankment is also performed under the varied strength of foundation soil which results from the increase of effective stress due to consolidation of the clay under the landfill. The predicted settlement from CONSOL is compared with the field measured settlement. The results show that, when the leachate level increases with the increase of waste height, the increase of the effective stress of foundation clay is negligible and the stability of the slope of the landfill may not be secured as the disposal of the waste proceeds. Several complementary repairworks, e. g. the reduction of current slope of the fill, application of drain methods to stop or reduce !he leachate level are recommended. The predicted settlement consists moderately with the field measured settlement.