• Tunnel and Underground Space
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• v.33 no.3
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• pp.141-149
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• 2023

Recently, as the demand for urban underground space increases, urban tunnel planning is actively progressing. In particular, the application of the roadheader excavation method, which has favorable applicability to urban tunnel, is increasing. However, it is known that the roadheader excavation method has a limitation in that excavation efficiency for high strength rock with a Uniaxial Compressive Strength (UCS) of 100 MPa or more is lowered. In this study, The pre-cracked method was presented as a method to improve the excavation efficiency of roadheader for high strength rock and its applicability was evaluated. The net cutting rate was evaluated using the Bilgin prediction formula, which can calculate the net cutting rate by considering the UCS and RQD (Rock Quality Designation). It was found that the net cutting rate increased as the RQD decreased under the rock condition with the same UCS. This is judged to increase the excavation efficiency of the roadheader in the jointed high strength rock. Additionally, the field applicability of the pre-cracked method for high strength rock was verified through field tests. It was confirmed that the crack zone was formed around the charging hole, and it is considered that the pre-cracked method can be applied to the high strength rock.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.1
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• pp.27-35
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• 2002

For the excavation of the rock, blast method is put into operation in most of the construction site in Korea. In comparison to other methods of excavation, blast method has many merits such as improvement in efficiency in operation, reducement of operation period, and etc. However, blast operation also creates much loss due to the blast vibration, noise, and fly rocks. Thus, in this study, we have examined main features, rock fragmentation effect and the application of plasma method the one of shallow vibration method. In this study, the attenuation exponent of blast method operated in the site was 1.39~1.40 and that of the plasma method was analysed to be 1.45~2.23. From the location where the distance between excavation location and observation location was over 15 m, most of excavation vibration were measured to be less than 0.2 kine(cm/sec), which is also the allowed standard value of sensitive buildings, such as cultural assets and computer facilities. According to the result of FFT(Fast Fourier Transform) analysis, the frequency measured through blast method in this site was 30~50 Hz and the frequency of plasma method ranges in between 30~130 Hz.

• Journal of Construction Engineering and Project Management
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• v.3 no.4
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• pp.1-4
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• 2013

Excavation is most commonly used activity in all construction projects. All contracting agencies prefer to use bigger and heavier excavators and dumpers on site to do excavations if quantity of excavation is huge. Estimation of required number of excavators and dumpers for completion of excavation could be rather a tedious process involving repetitive calculation on which professionals spend their valuable time. As the Information Technology is highly involved in construction section there os need to have IT model for estimation of number of excavators and dumpers. The developed model is useful to calculate required equipments within short period of time. The purpose of the developed IT model is to save the time and efforts of the construction professional. The paper discusses about model which can be used on site to estimate numbers of excavators and dumpers required for completion of certain quantity of excavation within the given time. The calculation considers various existing formulas and method to generate the output. This information could certainly be useful in planning equipments on construction project sites. The tool is user friendly where any non IT background person can use it on construction sites.

• Korean Journal of Agricultural Science
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• v.24 no.2
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• pp.226-236
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• 1997

The results obtained by elasto-plastic analysis method about the displacement, deformation and stability on the soft ground excavation using sheet pile were summarized as follows ; 1. In the case of strut 1 step, the maximum wall displacement value in the first and the second excavation was small, but it increase remarkably after the third excavation and when the excavation depth was 8m, the point of maximum wall displacement was shown 0.75H~0.8H. 2. The value of safety factor(Fs) was increased with increasing of the penetration depth of sheet pile, cohesion and internal friction angle of ground. Safety factor was mostly effected by penetration depth of sheet pile and more effected by cohesion than internal friction angle of ground. 3. Since the deformation of sheet pile of this ground from the results of analysis and measurement increased remarkabaly after 6m excavation depth, it was desirable that the point of strut installation was GL-6m. 4. Safe excavation depth on ground by analysis considered penetration depth, cohesion and internal friction was shown at the table 3.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.2
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• pp.133-141
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• 2007

The excavation damaged zone (EDZ) is an area around an excavation where in situ rock mass properties, stress condition, displacement, groundwater flow conditions have been altered due to the processes induced by the excavation. Various studies have been carried out on EDZ, but most studies have focused on the mechanical bahavior of EDZ by in situ experiment. Even though the EDZ could potentially form a high permeable pathway of groundwater flow, only a few studies were performed on the analysis of groundwater flow in EDZ. In this study, the 'hydraulic EDZ' was defined as the rock zone adjacent to the excavation where the hydraulic aperture has been changed due to the excavation by using H-M coupling analysis. Fundamental principles of distinct element method (DEM) were used in the analysis. In the same groundwater level, the behavior of hydraulic aperture near the cavern was analyzed for different stress ratios, initial apertures, fracture angles and fracture spacings by using a two-dimensional DEM program. We evaluate the excavation induced hydraulic aperture change. Using the results of the study, hydraulic EDZ was defined as an elliptical shape model perpendicular to the joint.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.5
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• pp.357-371
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• 2023

In cable tunnel construction using TBM, the vertical shaft is an essential structure for entrance and exit of TBM equipment and power lines. Since a shaft penetrates the ground vertically, it often encounters rock mass. Blasting or rock splitting methods, which are mainly used to the rock excavation, cause public complaints due to the noise, vibration and road occupation. Therefore, mechanical excavation using vertical shaft excavation machine are considered as an alternative to the conventional methods. However, at the current level of technology, the vertical excavation machine has limitation in its performance when applied for high strength rock with a compressive strength of more than 120 MPa. In this study, the potential utilization of waterjet technology as an excavation assistance method was investigated to improve mechanical excavation performance in the hard rock formations. Rock cutting experiments were conducted to verify the cutting performance of the abrasive waterjet. Based on the experimental result, it was found that ensuring excavation performance with respect to changing in ground conditions can be achieved by adjusting waterjet parameters such as standoff distance, traverse speed and water pressure. In addition, based on the relationship between excavation performance, uniaxial compressive strength and RQD, it was suggested that excavation performance could be improved by artificially creating joints using the abrasive waterjet. It is expected that these research results can be utilized as fundamental data for the introduction of vertical shaft excavation machines in the future.

• Journal of Korean Society of Disaster and Security
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• v.10 no.1
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• pp.11-17
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• 2017

The case study on ground subsidence was conducted and the cause of ground subsidence was evaluated, main cause were insufficient site exploration, inaccurate strength parameters, defective temporary wall, insufficient reaction for boiling and heaving, excessive excavation and so on. Risk factors during excavation were identified from the cause of ground subsidence and risk factors were site exploration, selecting excavation method, structure analysis, measurement plan, excavation method construction, underground water level change, natural disaster and construction management. The survey of the experts on risk factors identified was conducted to evaluate the importance of risk factors, and confidence analysis was performed to evaluate the significance level between survey result and survey respondent using Chi-square Test.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.345-352
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• 2022

The existing NATM (New Austrian Tunneling Method) has induced civil compliants due to blasting vibration and noise. Machanized excavation methods such as TBM (Tunnel Boring Machine) are being adopted in the planning and construction of tunneling projects. Shield TBM method is composed of repetition processes of TBM excavation and segment installation, the machine has to be stopped during the later process. Consecutive excavation technology using helical segment is under developing to minimize the stoppage time. The modification of thrust jacks and module are planned to ensure the advance force acting on the inclined surface of helical segment. Also, the integrated system design of hydraulic circuit will be remodeled. This means that the system deactivate the jacks on the installing segment while the others automatically act the thrusting forces on the existing segments. This report briefly introduces the mechanical research part of the current consecutive excavation technological development project of TBM.

• Explosives and Blasting
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• v.28 no.1
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• pp.63-70
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• 2010

This study is investigated the extent of the noise and ground vibration in an adjacent zone of a cattle pen and an antiquated housing structures for judgement of the spot applicability on the extents of the noise and ground vibration of the rock-splitting method by an oil pressure. It is studied by measuring and analysing in an adjacent position the extents of the noise and ground vibration according to the work process of the rock-splitting method, such as drilling, rock-splitting, arranging rock, loading and by being compared with the permitted level on the noise and ground vibration fixed at the spot. To the results, it is identified that the influence to the noise has to be considered, even if the rock-splitting method is applied as an excavation method to lower a ground vibration by the classification on blasting method of the ministry of land, transport and marine affairs.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.511-524
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• 2016

Since a room-and-pillar underground structure is characterized by its grid-type array of room and pillar, its economical efficiency can be governed by excavation sequence. In this study, the construction period by the drill-and-blast method as a excavation method for a room-and-pillar underground structure was examined. In addition, the parallel excavation sequence was considered as the main sequence of a room-and-pillar underground structure. Sequences of mucking and support installation were derived to estimate the total excavation cycle by taking the case of a road tunnel into consideration. From the excavation cycle of room-and-pillar underground structure, the relationship between available maximum and minimum numbers of jumbo drill machines depending on the number of faces in operation was suggested.