Eun-Chul Shin

Reinforcement and Arching Effect of Geogrid-Reinforced and Pile-Supported Embankment on Marine Soft Ground

The effectiveness of constructing a geogrid-reinforced and pile supported embankment on soft ground to reduce differential settlement has been studied by pilot scale field tests and numerical analysis. Three-by-three pile groups with varying pile spacing were driven into a layer of soft ground, and a layer of geogrid was used as reinforcement over each pile group. Further, a 2-D numerical analysis has been conducted using the computer program FLAC 2D. The mechanisms of load transfer can be considered as a combination of embankment soil arching, geogrid tension, and stress transfer due to the difference in stiffness between pile and soft ground. Based on the pilot scale field tests and results of numerical analysis, we find that the geosynthetic reinforcement slightly interferes with soil arching, and helps reduce differential settlement of the soft ground. Also, the most effective load transfer and vertical stress reduction at the midspan between piles occurs when the pile cap spacing index D/b (D: pile cap spacing, b: diameter of pile) is 3.0.

Design of dualband metamaterial bandpass filter using zeroth order resonance

This paper proposes the design method based on the composite right/left-handed (CRLH) structure to miniaturize and generate the dual-band characteristic. For realization, we used the zero-th order resonance point of the CRLH and the simple theory of Inverter. The proposed technique is validated by the performance predictions and experiments, and it is found out that the suggested method enables the huge size reduction from the conventional filters such as the parallel coupled type which was designed following the half-wavelength resonance.

A UWB antenna combined with the CRLH metamaterial UWB bandpass filter having the bandstop at the 5 GHz-band WLAN

This paper investigates how a Ultrawide Band(UWB) antenna can get the stopband created by the UWB filter which has a notch at the 5 GHz-band WLAN(Wireless Local Area Network) service. Particularly, we proposed the design of the Composite Right- and Left-Handedness(CRLH) metamaterial UWB notched-bandpass filter to have the smallest component possible connected to the feedline of the UWB antenna. We will see the λ/9-long UWB filter with and without the notch, and the acceptable VSWRs of the UWB antenna before and after being combined with the notched metamaterial UWB filter.

Automated stability analysis of slopes stabilized with piles

This paper pertains to the application of optimization technique in the stability analysis of creeping slopes reinforced with passive piles. A method of stability analysis of the pile-reinforced slopes has been derived by extending the friction circle method of slope stability analysis in conjunction with the pile stability analysis proposed by Ito and Matsui. The problem has been cast into a mathematical programming. The solutions have been isolated by formulating the problem as one of non-linear programming. The applicability of the developed method has been verified by comparing the predicted failure surfaces with those results, reported in literature.

A Study on The Frost Penetration Depth of Pavement with Field Temperature Data

The frost penetration depth of pavement is usually estimated from the freezing index that made temperature data analysis of 30 years and decided the thickness of anti-frost layer. The field monitoring region in study was divided into five regions by freezing index 550~650day, 450~550day and 350~450day. Each region has three-section of road pavement such as cutting area, boundary area of cutting and banking, and lower area of banking. The field monitoring system was established both in the section of anti-frost layer and in the section without anti-frost layer. The data analysis was conducted for determination of frost penetration depth within the paved road by the field monitoring system. The result showed that The temperature of subgrade without anti-frost layer shows below zero in centigrade for the region of freezing index 550~650day, up and down around zero degree in subgrade for the region of freezing index 450~550day, and there is no place existed below zero degree in subgrade for the region of freezing index below 450day. With comparison of field frost penetration depth for the cross-sections of pavement, the cutting area shows the greatest frost penetration depth, and less influence of frost penetration depth for the boundary area of cutting and banking, and the least influenced for the lower area of banking.

Ultimate bearing capacity of strip foundation on geogrid-reinforced clay slope

Laboratory model results for the ultimate bearing capacity of a surface strip foundation on a saturated slope reinforced with geogrid layers are presented. The angle of the slope with the horizontal was varied from 35° to 50°.A biaxial geogrid was used as reinforcement for all of the model tests. The location of the top geogrid layer with respect to the bottom of the foundation, center-to-center spacing of the geogrid layer, and depth of geogrid reinforcement were varied. Based on the model test results a preliminary outline for estimating the ultimate bearing capacity is presented.

The compact UHF CT-type Bandpass filter with a mixed coupling

This paper presents the design of the compact UHF Bandpass filter of CT-type with a novel mixed coupling topology. In further detail, this new coupling structure mathematically equals the transmission zero that enables particularly the better rejection performance in the stopband without increasing the filters order. To envision this design concept, we fabricated a microstrip filter whose measurement proves to agree with the predicted performance and the suggested coupling structure reduces the overall size, and will be possibly used in the miniaturized UHF apparatus such as the RFID system.

Development of Underground Tunnel Construction Technology in Weak Rock

The construction of tunnel has a long history from the mining tunnel for minerals to underground passage for transportation. Most of tunnels are being constructed to pass through the high mountain to have a shortcut instead of taking a detour to reach the destination. The geological conditions in the area of tunnel construction work are not all the time favorable condition. The rock bolt and steel rib support systems for tunnel face are described. The tunnel construction in weak rock is described with rock bolt and steel pipe grouting reinforcement (NATM). The advantages and construction procedures of pre-supported tunneling method (PSTM) and tubular roof construction method (TRcM) in soft ground are presented with the detail schematic diagrams. In the latter part of this paper, the field application case histories of PSTM and TRcM are reported for the tunnel construction for road in weak rock and metro station in soft ground, respectively. The field monitoring results during the tunnel construction which underpass through 60-m-long existing railway tracks by using TRcM are also described.

Design of a modified monopole antenna for the quadband communication

A modified monopole antenna is proposed for multi-band personal wireless communication handsets with triple-resonant operation. This antenna consists of a main radiator, a bent tuning stub, an U-shaped slit, a shorting strip line, and a narrow resonant slit, and occupies a total volume of 36 × 15.8 × 6 mm3. The first resonant frequency is decided by the main radiator of the antenna, and the second one is controlled by the length of a bent tuning stub. The third resonant frequency is generated by inserting a narrow resonant slit in a perimeter of the main radiator. Three resonant frequencies of the designed antenna can be independently controlled by tuning the length of individual element of the proposed antenna. The bands of the implemented antenna are GSM900, DCS1800, US-PCS, and S-DMB.

Evaluation of Discharge Capacity with Various Vertical Drain Core Types

Recently, the demand of suitable land for industrial complex and residential area is being increased with the economic growth, but it is difficult to acquire the areas for development with good ground condition. For efficient and balanced development of land, new development projects are being carried out not only the areas with inland but also those with the soft ground as well. Perfabricated vertical drain technology is widely used to accelerate the consolidation of soft clay deposits and dredged soil incorporated with pre-loading. Several types of prefabricated vertical drains (PVDs) are used in the field. The discharge capacity is the most important factors of PVDs and affect to the consolidation behavior. However, under the field conditions, discharge capacity is changed with various reasons, such as soil condition, confinement pressure, long-term clogging, folding of vertical drains, and so on. Therefore, many researchers and engineers recommend the use of required discharge capacity. In this paper, the experimental study was carried out to obtain the discharge capacity of six different types of PVDs by utilizing the large-scale laboratory apparatus and the required discharge capacity was calculated by several different theoretical methods.