• Steel and Composite Structures
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• v.20 no.3
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Journal of Welding and Joining
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• v.7 no.2
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• pp.35-48
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• 1989

This study is concerned with a correlation of microstructure and local brittle zone (LBZ) in offshore structural steel welds. The influence of the LBZ on fracture toughness was investigated by means of simulated heat-affected zone (HAZ) tests as well as welded joint tests. Micromechanical processes involved in void and cleavage microcrack formation were also identified using notched round tensile tests and subsequent SEM observations. The LBZ in the HAZ of a multiphase welded joint is the interstitially reheated coarse grained HAZ, which is influenced by metallurgical factors such as effective grain size, the major matrix structure and the amount of high-carbon martensite-austenite (M-A) constituents. The experimental results indicate that Chirpy energy was found to scale monotonically with the amount of M-A constituents, confirming that the M-A constituent is the major microstructural factor controlling the HAZ toughness. In addition, voids and microcracks are observed to initiate at M-A constituents by the shear cracking process. Thus, the M-A constituent played an important role in initiating the voids and microcracks, and consequently caused brittle fracture.

• Geomechanics and Engineering
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• v.21 no.3
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• pp.289-300
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• 2020

Estimating the damage induced by an explosion around a blast hole has always been a challenging issue in geotechnical engineering. It is difficult to determine an exact dimension for damage zone since many parameters are involved in the formation of failures, and there are some uncertainties lying in these parameters. Thus, the present study adopted a probabilistic approach towards this problem. First, a reliability model of the problem was established and the failure probability of induced damage was calculated. Then, the corresponding exceedance risk curve was developed indicating the relation between the failure probability and the cracked zone radius. The obtained risk curve indicated that the failure probability drops dramatically by increasing the cracked zone radius so that the probability of exceedance for any crack length greater than 4.5 m is less than 5%. Moreover, the effect of each parameter involved in the probability of failure, including blast hole radius, explosive density, detonation velocity, and tensile strength of the rock, was evaluated by using a sensitivity analysis. Finally, the impact of the decoupling ratio on the reduction of failures was investigated and the location of its maximum influence was demonstrated around the blast point.

• Nuclear Engineering and Technology
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• v.56 no.2
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• pp.485-497
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• 2024

Ring beam is the main anchorage zone of the tendons in the nuclear power prestressed concrete containment vessel (PCCV). Its safety is crucial and has a great influence on the overall performance of PCCV. In this paper, two half-scale ring beams were tested to investigate the mechanical performance of the anchorage zone in the PCCV under multidirectional pressure. The effect of working condition with different tension sequences was investigated. Additionally, a half axisymmetric plane model of the containment was established by the finite element simulation to further predict the experimental responses and propose the local reinforcement design in the anchorage zone of the ring beam. The results showed that the ultimate load of the specimens under both working conditions was greater than the nominal ultimate tensile force. The original reinforcement design could meet the bearing capacity requirements, but there was still room for optimization. The ring beam was generally under pressure in the anchorage area, while the splitting force appeared in the under-anchor area, and the spalling force appeared in the corner area of the tooth block, which could be targeted for local strengthening design.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.37-45
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• 2010

Surfactant-enhanced ozone sparging (SEOS), an advanced version of SEAS (surfactant-enhance air sparging) was introduced in this study for the first time for removal of non-volatile contaminant from aquifer. The advantages of implementing SEAS, enhanced air saturation and expanded zone of sparging influence, are combined with the oxidative potential of ozone gas. Experiments conducted in this study were tow fold; 1-dimensional column experiments for the changes in the gas saturation and contaminant removal during sparging, and 2-dimensional box model experiment for the changes in the size of zone of influence and contaminant removal. An anionic surfactant (SDBS, sodium dodecylbenzene sulfonate) was used to control surface tension of water. Fluorescein sodium salt was used as a representative of watersoluble contaminants, for its fluorescence which is easy to detect when it disappears due to oxidative degradation. Three different gases (air, high-concentration ozone gas, and low-concentration ozone gas) were used for the sparging of 1-D column experiment, while two gases (air and low-concentration ozone gas) were used for 2-D box model experiment. When SEOS was performed for the column and box model, the air saturation and the zone of influence were improved significantly compared to air sparging without surface tension suppression, resulted in effective removal of the contaminant. Based on the experiments observations conducted in this study, SEOS was found to maintain the advantages of SEAS with further capability of oxidative degradation of non-volatile contaminants.

• Geomechanics and Engineering
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• v.21 no.2
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• pp.187-200
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• 2020

In the current work, a series of three-dimensional finite element analyses have been conducted to investigate the behaviour of pre-existing single piles in response to adjacent tunnelling by considering the tunnel face pressures and the relative locations of the pile tips with respect to the tunnel. Via numerical modelling, the effect of the face pressures on the pile behaviour has been analysed. In addition, the analyses have concentrated on the ground settlements, the pile head settlements and the shear stress transfer mechanism at the pile-soil interface. The settlements of the pile directly above the tunnel crown (with a vertical distance between the pile tip and the tunnel crown of 0.25D, where D is the tunnel diameter) with a face pressure of 50% of the in situ horizontal soil stress at the tunnel springline decreased by approximately 38% compared to the corresponding pile settlements with the minimum face pressure, namely, 25% of the in situ horizontal soil stress at the tunnel springline. Furthermore, the smaller the face pressure is, the larger the tunnelling-induced ground movements, the axial pile forces and the interface shear stresses. The ground settlements and the pile settlements were heavily affected by the face pressures and the positions of the pile tip with respect to the tunnel. When the piles were inside the tunnel influence zone, tensile forces were induced on piles, while compressive pile forces were expected to develop for piles that are outside the influence zone and on the boundary. In addition, the computed results have been compared with relevant previous studies that were reported in the literature. The behaviour of the piles that is triggered by adjacent tunnelling has been extensively examined and analysed by considering the several key features in substantial detail.

• Journal of Soil and Groundwater Environment
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• v.19 no.3
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• pp.1-14
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• 2014

It is necessary to decide the pumping rate and pumping well location together with the capture zone in order to determine an appropriate groundwater remediation strategy to manage the contaminated groundwater. The relationship between the capture zone and the drawdown radius of influence ($ROI_s$) was considered. $ROI_{cs}$ is defined as the distance where the criteria of drawdown is cs meter from pumping well in this paper. A method to decide the required pumping rate for the remediation of contaminated groundwater in order to create appropriate $ROI_{cs}$ is suggested by using the Theis equation (1935) and Cooper-Jacob equation (1946). It was shown in this study that $ROI_{cs}$ is in proportion to the pumping rate and the criteria of drawdown, which decides $ROI_{cs}$, is inversely proportional to Ti value (transmissivity ${\times}$ hydraulic gradient). The pumping rate which creates the required $ROI_{cs}$ could be planned through the relationship between the $ROI_{cs}$ and pumping rates ($ROI_{cs}$-Q curve) of the field sites 1, 2 and 3. If the drawdown is investigated along with Ti value and pumping rate at a specific site where pump and treat remediation is planned, it is expected that the required criteria of drawdown can be evaluated by using the relationship between the cs and Ti (cs-Ti curve).

• Tunnel and Underground Space
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• v.23 no.5
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• pp.392-400
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• 2013

Joint sets should be considered as an influence factor, when location of subsidence zone by stopes is predicted. And the mechanical properties and distribution patterns of joint set above stopes may be affecting subsidence occurrence. In this study, therefore, the orientation of joint sets is reanalyzed with the data from the previous research on prediction of defining the subsidence zone. From a correlated analysis, the influence of major joint set($J_1$) on subsidence location was analyzed by comparing the angle of assumption with the angle of major joint set($J_1$).

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1136-1143
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• 2008

The Vertical Drains(Sand Drains, Pack Drain, PBD) is used for Vertical Drains Method in domestic. Each of the drains is selected after it consider a field condition and efficiency of drain. A discharge capacity is very important factor, which to estimate a efficiency. And the smear Zone where disturbance area of in-suit by installation of Vertical Drains is important factor to select a drains. In this study, the complex discharge capacity test was operated for discharge capacity comparison of the Wing Drain and PBD. And a model test was operated to apprehend smear zone of the Wing Drain and PBD. From these tests, it was apprehended an engineering characteristic of vertical drain. The results of the complex discharge capacity test, a discharge capacity fell below $20cm^3/sec$ to $1cm^3/sec$ in more than overburden load $2.5kg/cm^2$. The Wing Drain maintained a over $40cm^3/sec$ in more than overburden load $2.5kg/cm^2$ and minimum discharge capacity $8cm^3/sec$. The results of the smear zone test, a influence bounds of smear zone was more larger in case of the Wing Drain(rectangle) than the PBD. But when a discharge capacity of Wing Drain is considered, it was concluded which smear zone bounds difference was effected in comparison with PBD. I think that it minimized a mandrel section to minimize a smear zone effect range

• Journal of the Korean GEO-environmental Society
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• v.16 no.6
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• pp.13-22
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• 2015

In the current work, a series of three-dimensional (3D) numerical modelling has been performed in order to study the effects of the relative locations of tunnels with respect to the position of pile tips which governs the behaviour of pre-existing, adjacent single piles. In the numerical analyses, several governing factors, such as tunnelling-induced pile head settlements, relative displacements, volume losses, axial pile forces, interface shear stresses and apparent factors of safety have been analysed. When the pile tips are inside the tunnelling influence zone, of which the pile tip location is considered with respect to the tunnel position, tunnelling-induced pile head settlements are larger than the ground surface settlements, resulting in tunnelling-induced tensile pile forces. On the contrary, when the pile tips are outside the influence zone, compressive pile forces associated with downward shear stresses at the upper part of the piles are developed. Based on computed load and displacement relation of the pile, the apparent factors of safety of the piles inside the tunnelling influence zone have been reduced by 36% in average. The shear transfer mechanism based on the relative tunnel locations has been analysed in great detail by considering tunnelling-induced pile forces, interface shear stresses and the apparent factors of safety.