• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.4_2
• /
• pp.603-609
• /
• 2022

Bottom hole assembly(BHA) is a key component of the drilling system, consisting of various components and tools(including the drill bit and mud motor) which operate at the bottom of the wellbore and physically drill the rock. This paper investigates the dynamic characteristics of the mud motor which is a drilling propulsion tool. And computational structural analysis is performed to calculate the von-Mises stress and the safety factor of components constituting the mud motor. In this process, the field test data of onshore drilling are used for analysis.

• Structural Engineering and Mechanics
• /
• v.69 no.5
• /
• pp.537-545
• /
• 2019

Stress analysis of bottom-hole rock has to be considered with much care to further understand rock fragmentation mechanism and high penetration rate. This original study establishes a fully coupled simulation model and explores the effects of overburden pressure, horizontal in-situ stresses, drilling mud pressure, pore pressure and temperature on the stress distribution in bottom-hole rock. The research finds that in air drilling, as the well depth increases, the more easily the bottom-hole rock is to be broken. Moreover, the mud pressure has a great effect on the bottom-hole rock. The bigger the mud pressure is, the more difficult to break the bottom-hole rock is. Furthermore, the maximum principal stress of the bottom-hole increases as the mud pressure, well depth and temperature difference increase. The bottom-hole rock can be divided into three main regions according to the stress state, namely a) three directions tensile area, b) two directions compression areas and c) three directions compression area, which are classified as a) easy, b) normal and c) hard, respectively, for the corresponding fragmentation degree of difficulty. The main contribution of this paper is that it presents for the first time a thorough study of the effect of related factors, including stress distribution and temperature, on the bottom-hole rock fracture rather than the well wall, using a thermo-poroelastoplasticity model.

• Geomechanics and Engineering
• /
• v.16 no.1
• /
• pp.105-112
• /
• 2018

This paper presents results of a compressive investigation conducted on weathered soil stabilized with ground bottom ash (GBA) and red mud (RM). The effects of water/binder ratio, RM/GBA ratio, chemical activator (NaOH and $Na_2SiO_3$) and curing time on unconfined compressive strength of stabilized soils were examined. The results show that the water/binder ratio of 1.2 is optimum ratio at which the stabilized soils have the maximum compressive strength. For 28 days of curing, the compressive strength of soils stabilized with alkali-activated GBA and RM varies between 1.5 MPa and 4.1 MPa. The addition of GBA, RM and chemical activators enhanced strength development and the rate of strength improvement was more significant at the later age than at the early age. The potential environmental impacts of stabilized soils were also assessed. The chemical property changes of leachate from stabilized soils were analyzed in terms of pH and concentrations of hazardous elements. The observation revealed that the soil mixture with ground bottom ash and red mud proved environmentally safe.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.16 no.3
• /
• pp.260-264
• /
• 1983

Organic matters as COD, ignition loss, phaeophytin pigment, and sulfide in the superficial bottom mud in the shellfish farms during summer in 1981 were determined to find an eutrophication level for the conservation of the farms. Both the Goseong Bay and the Jaran Bay, which are productive shellfish farms, are located along the southern coast of the Korean Peninsula. The Goseong Bay is 8m deep with a narrow mouth and approximately $17.5km^2$ in area, and the Jaran Bay 10m deep with $27.3km^2$. The bottoms are silty. Major shellfishes cultured are the oyster by the off-bottom method and the arkshell in the bottom. COD contents were $12.5{\sim}19.5\;mg/g$ dry mud, ignition loss $6.70{\sim}11.83\%$, phaeophytin pigment $6.8{\sim}11.0{\mu}g/g$ dry mud, and sulfide $0.18{\sim}0.64{\mu}g/g$ dry mud. There were no significant differences in the determined quantities between two bays. All quantities except the sulfide which is a little over than an eutrophication level, 0.3 mg/g dry mud, shows that the bottom muds are in an early stage of eutrophication. In addition, there was no particular increase in quantities of aforementioned four paramenters in comparision with those of 1976. It means that the eutrophication in the Goseong-Jaran Bay makes slow progress.

• Geomechanics and Engineering
• /
• v.13 no.6
• /
• pp.1011-1025
• /
• 2017

The geological conditions surrounding the Jijiapo Tunnel of the Three Gorges Fanba Highway project in Hubei Province are very complex. In this paper, a 3-D physical model was carried out to study the evolution process of filling-type fracture water inrush and mud gush based on the conditions of the section located between 16.040 km and 16.042 km of the Jijiapo Tunnel. The 3-D physical model was conducted to clarify the effect of the self-weight of the groundwater level and tunnel excavation during water inrush and mud gush. The results of the displacement, stress and seepage pressure of fracture and surrounding rock in the physical model were analyzed. In the physical model the results of the model test show that the rock displacement suddenly jumped after sustainable growth, rock stress and rock seepage suddenly decreased after continuous growth before water inrushing. Once water inrush occured, internal displacement of filler increased successively from bottom up, stress and seepage pressure of filler droped successively from bottom up, which presented as water inrush and mud gush of filling-type fracture was a evolving process from bottom up. The numerical study was compared with the model test to demonstrate the effectiveness and accuracy of the results of the model test.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.1
• /
• pp.78-87
• /
• 2003

High-frequency (126-㎑) bottom backscattering measurements with various bottom types were conducted at the water tank in Ocean Acoustic Laboratory, Hanyang University. For the purpose of investigating the energy distribution of bottom scattering with various bottom types, the sediment was varied with gravel, sand, sandy mud and mixed bottoms. To examine the anisotropic nature of the scattering due to the orientations of bottom ripple, the footprints were made transverse and longitudinal to the direction of incident wave. The total scattering characteristics are that the larger grazing angles the larger backscattering strengths become and backscattering strengths for a transverse ripple case are higher than those of longitudinal ripple case. finally, the variations of scattering strength depend mainly on the ripple's orientation.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.11 no.4
• /
• pp.243-247
• /
• 1978

COD and sulphide contents in the superficial mud in three oyster farms, one near Gajo-do in Chinhae Bay, the second near Eup-do in Koseong Bay and the third near Eogu in Keoje Bay, around the Chungmu area have been monthly determined for seven months from May through November in 1978. Bottom water was also checked for chlorophyll-a, dissolved oxygen, COD and sulphide. In general, large amounts of COD and sulphide in the superficial mud were found in the summer season, COD was 38.1 mg/g dry mud in the farm near Gajo-do, 32.3 mg/g near Eup-do and 25.1 mg/g in Eogu farm and sulphide was 0.313 mg/g dry mud, 0.517 mg/g and 0.132 mg/g respectively. COD and sulphide contents in the farms near Gajo-do and Eup-do were a little over the upper level of the eutrophic range, that is, 30 mg/g dry mud in COD and 0.3 mg/g dry mud in sulphide. It shows that the above two oyster farms were already eutrophicated. However, among three oyster farms no clear difference in bottom water was found.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.21 no.1
• /
• pp.41-46
• /
• 2011

The artificial aggregates (AAs) composing of 2 wastes, coal bottom ash and dredged soil (7 : 3, weight ratio) were fabricated as a function of red mud contents,0~30 wt% using direct sintering method at $1050{\sim}1250^{\circ}C$ for 10 min, and those physical properties were evaluated. Especially, in order to analyze the red mud addition effect on the bloating phenomenon of AAs manufactured, the specific gravity and water absorption were measured and studied linked with the microstructural observation results. The lightening of AAs was enhanced due to increased bloating with increasing temperature and red mud contents. The AAS sintered at $1050{\sim}1150^{\circ}C$ showed well-developed black-coring structure, but for the specimens containing red mud sintered over $1200^{\circ}C$ generated excessive liquid and gas caused by reduction of $Fe_2O_3$, thus the black-coring part was gradually burst open out of shell of AAs. Particularly, all specimens containing 30 wt% red mud was burst up when sintered over $1100^{\circ}C$. The AAs containing no red mud sintered at $1200^{\circ}C$ had a specific gravity of about 1.2 and those containing 20 wt% had below 1.0 which are characters of lightweight aggregate.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.35 no.3
• /
• pp.273-281
• /
• 2002

Determination of sediment type is generally based on ground truthing. This method, however, provides information only for the limited sites. Recent developments of remote classification of seafloor sediments made it possible to obtain continuous profiles of sediment types. QTC View system, which is an acoustic instrument providing digital real-time seabed classification, was used to classify seafloor sediment types in the Suyoung Bay, Pusan. QTC View was connected to 50 kHz echo sounder, All parameters of QTC View and echo sounder are uniformly kept during survey. By ground truthing, the sediments are classified into seven types, such as slightly gravelly sand, slightly gravelly sandy mud, gravelly muddy sand, clayey sand, sandy mud, slightly gravelly muddy sand, and rocky bottom. By the first remote classification using QTC View, four sediment types are clearly identified, such as slightly gravelly sand, gravelly mud, slightly gravelly muddy sand, and rocky bottom. These are similar to the result of the second survey. Also the result of remote classification matches well with that of ground truthing, but for sediment type determined by minor component. Therefore, QTC View can effectively be used for remote classification of seafloor sediments.

• Economic and Environmental Geology
• /
• v.11 no.2
• /
• pp.81-88
• /
• 1978

Nearly 300 bottom sediments and 20 box-cores were sampled from the Asan bay. The central portion of the Asan bay is covered by sand, slightly gravelly sand and gravelly muddy sand. Between the central and marginal zones gravelly mud and slightly gravelly sandy mud are characteristically distributed. The gravel population in the sediments seems to be originated from the rocky bottom on the area near the bay because the gravel is angular and composed of the schist and gneiss. The quartz/feldspar ratio is about 3/2. It is considered to be that the amount of feldspar in this bay is much higher than that of any other areas in the Yellow Sea. This is considerd to be comparatively short distance of transport ion of these sediment from the provenance.