Inspection Holes Research Articles

Inspection Operations and Hole Detection in Fish Net Cages through a Hybrid Underwater Intervention System Using Deep Learning Techniques

Net inspection in fish-farm cages is a daily task for divers. This task represents a high cost for fish farms and is a high-risk activity for human operators. The total inspection surface can be more than 1500 m2, which means that this activity is time-consuming. Taking into account the severe restrictions for human operators in such hostile underwater conditions, this activity represents a significant area for improvement. A platform for net inspection is proposed in this work. This platform includes a surface vehicle, a ground control station, and an underwater vehicle (BlueROV2 heavy) which incorporates artificial intelligence, trajectory control procedures, and the necessary communications. In this platform, computer vision was integrated, involving a convolutional neural network trained to predict the distance between the net and the robot. Additionally, an object detection algorithm was developed to recognize holes in the net. Furthermore, a simulation environment was established to evaluate the inspection trajectory algorithms. Tests were also conducted to evaluate how underwater wireless communications perform in this underwater scenario. Experimental results about the hole detection, net distance estimation, and the inspection trajectories demonstrated robustness, usability, and viability of the proposed methodology. The experimental validation took place in the CIRTESU tank, which has dimensions of 12 × 8 × 5 m, at Universitat Jaume I.

Case Study on the Method of Rock Mass Overburden Consolidation Grouting for Dam Foundation

Conventional grouting methods present challenges in achieving effective surface rock grouting and avoiding interference with concrete grouting and construction processes. The proposed approach includes reserving rock overburden, controlling grouting pressure and concentration, using a segmented grouting method, and selecting appropriate materials to develop a key method for consolidation grouting. This method not only overcomes the problems associated with the conventional consolidation grouting method but also effectively protects the thin layer of breccia lava in the Baihetan Dam foundation and solves the problem of unloading and relaxation of columnar jointed basalt caused by exposed consolidation grouting. The results show that the post grouting inspection hole permeability qualification rate is 99.3%, with the proportion of high-speed measuring points of various rock types ranging from 91.8% to 93.3%, and the proportion of low-speed measuring points ranging from 2.0% to 2.9%. The drop rate of the grout take of sequence I and sequence II is between 30%–60%, except for some dam sections. These results indicate that the proposed method for consolidation grouting meets the design requirements. The findings have significant implications for the design and construction of consolidation grouting in similar projects.

Research on Sustainable Mining and Water Prevention in Large Open-Pit Water Deposits

Due to the impacts on the ecological environment, production safety and the economic benefits of large open-pit water deposits, there is no longer a single drainage method within the pit that can be used to meet the need for further deep mining. Therefore, curtain grouting technology is proposed for use in the prevention and control of mine water. The flow control equation of slurry in vertical fissures under the influence of self-weight stress was derived, and a three-dimensional visualized laminated jointed rock grouting model was developed independently to study the slurry transport mechanism, diffusion pattern, and sealing mechanism, which verified the correctness of the control equation. Field trials of industrial curtain grouting were also carried out at the mines, and the effectiveness of curtain water blockage was tested using visual analysis, inspection hole detection, and geophysical exploration methods. The results showed that after grouting the curtain, water-conducting cracks in the formation can be filled well and sealed, and the curtain has a good water-blocking effect. A complete set of diversified value-taking grouting systems is obtained, which can ensure the development of a green, safe and sustainable mine in the future.

Experimental Studies and Numerical Simulations of FRP Poles Failure in the Area of Inspection Hole

Glass fiber-reinforced polymer (GFRP) utility poles are becoming more widespread in European countries. To ensure the integrity and safety of poles, it is necessary to carefully examine their structural features. The purpose of this paper is to present the numerical model of a column made with the engineering simulation software ANSYS and to compare the experimentally determined values of the stresses that lead to column failure close to the inspection hole with the results obtained using the numerical model. The critical buckling and failure loads for GFRP poles, as well as the associated modes of failure, were correctly predicted by the finite element method used in this study. Failure occurred in the middle of the inspection hole's longer edge at a stress level of 220-250 MPa. A comparison of the stress using the ANSYS simulation software that led to the destruction of the column with those measured experimentally using strain gauges revealed a good agreement between their values.

Quantitative Identification of Grouting Effect of Working Face Floor with Multifactor Set

The deep coal mining in the North China type of coalfield is generally threatened by the underlying limestone water of Taiyuan Formation and Ordovician. The occurrence of water inrush can be avoided effectively by applying grouting reinforcement technology to the coal floor. However, the reinforcement treatment of the coal floor belongs to underground concealment engineering, and it is of great significance for the safe production of the coal mine by scientifically and comprehensively evaluating the technical method of the grouting effect on the working face floor. In this study, the optimal transfer matrix is used to construct the judgment matrix that meets the consistency requirements; the analytic hierarchy process is improved; and the grouting effect of the working face floor is evaluated by fuzzy comprehensive evaluation based on several factors of the grouting effect. Taking the grouting engineering of the 15092 working face of the Guhanshan Mine as an example, the evaluation of the grouting effect based on four evaluatory indices have been refined: dynamic hydrological features, grout amount, grouting inspection hole, and geophysical prospecting have been refined. Based on the improved analytic hierarchy process (AHP), the result of the grouting effect can be divided into four levels: distinction, good, average, and poor. The study would play a very important role in the evaluation of the grouting reinforcement of the working face floor and the practice of coal mine production safety.

Experimental Study of CO2-ECBM by Injection Liquid CO2

Coal mine gas disasters have severely restricted production safety. Improving gas extraction efficiency can effectively reduce disasters. Scholars have confirmed that CO2 successfully displaces coal seam CH4. This study conducted displacement and in situ experiments and compared gas drainage under different injection pressures. The displacement experiments indicated that CH4 production rates increased under increased pressures while the displacement ratios decreased. The pressure had a positive effect on sweep efficiency. The in situ experiment showed that CH4 and CO2 concentration trends in the inspection hole remained consistent. Through observing the data of the original and inspection holes, the average gas drainage concentration during low- and medium-pressure injections increased by 0.61 times and 1.17 times, respectively. The low-pressure average gas drainage scalar was increased by 1.08 times. During the medium-pressure injection, the average gas drainage purity increased by 1.94 times. The diffusion ranges of CO2 under low- and medium-pressure injections were 20–25 m and 25–30 m, respectively. The sweep efficiency of medium-pressure injection was 26% better than that of the low-pressure injection, with average pressures of 2.8 MPa and 1.4 MPa, respectively, for sweep efficiency. This study proposes an effective method for improving coal mine gas drainage efficiency.

An Integrated Evaluation Method for the Grouting Effect in Karst Areas

Our proposed integrated evaluation method for the grouting effect in karst areas is based on the cloud model (CM), the analytic hierarchical process (AHP), and a fuzzy comprehensive evaluation system. Our method fully considers the fuzziness and randomness of the evaluation indices, and bridges the gap between qualitative information and a quantitative evaluation value. The evaluation index system for the grouting effect is established by integrating metrics related to the construction technology, apparent parameters, and observational data from inspection holes and geophysical exploration techniques. First, the weight of each index is calculated using the AHP, which has been modified by the CM. Then, we calculate the cloud model membership degree for each index. Finally, we determine the comprehensive evaluation level by examining the similarity measures between the various cloud models. In this case study, we use our integrated method to evaluate the initial results of the grouting treatment project in the China Resources Cement (Pingnan) Limestone Mine. Our results are validated by subsequent monitoring results for this project. This study provides valuable insight into the treatment of water inflow in karst areas.

Field Test Research on Film Bag Grouting in Strongly Weathered Stratum Overlying Subway

A strongly weathered stratum needs to be reinforced by grouting before tunnel excavation due to its poor self-stability. This work studied the law of surface uplift caused by grouting in a strongly weathered stratum overlying a subway. A strongly weathered stratum overlying a subway section was taken as the research object, and the field test method was used to reveal the time and space variation characteristics of the surface uplift with grouting reinforcement. Then, the influence of the grouting reinforcement technology, quantity, and material on the maximum surface uplift value in the practical grouting process was analyzed. The results show the following. Regardless of whether film bag grouting is used or not, the uplift value of the monitoring points is directly proportional to time, and the growth rate of the uplift value tends to accelerate. The spatial distribution of the surface uplift is mainly related to its distance to the grouting point. In addition, the maximum uplift value of the film bag grouting technology is 32.1% lower than that of the ordinary grouting technology; given the same grouting materials and technology, the grouting amount increases by 50%, and the surface uplift value increases by 121%. Moreover, the C-S slurry exhibits rapid setting, a small diffusion range, and a large thickness of the grouting vein; the surface uplift value of the C-S slurry is 3.08 times that of the cement slurry. The field test research conclusion is applied to practical engineering, where the final uplift value is 1.8 to 2.5 cm, and the average permeability coefficient of the inspection hole is 3.52×10−7 cm/s, which reflects a good engineering governance effect.

Case Study: In Situ Experimental Investigation on Overburden Consolidation Grouting for Columnar Jointed Basalt Dam Foundation

The dam foundation rock mass, at the Baihetan hydropower station on the Jinsha River, is mainly columnar jointed basalt, with faults and fissures developed. Considering adverse factors such as the unloading relaxation or the opening of the fissures due to excavation blasting, consolidation grouting is needed to improve the integrity of the dam foundation rock mass. According to the physical and mechanical properties of columnar jointed basalt and the continuity of construction, the effectiveness of overburden consolidation grouting is experimentally studied. The results show that this grouting technology can obviously improve the integrity and uniformity of a dam foundation rock mass and reduce the permeability of the rock mass. After grouting, the average increase in the wave velocity of the rock mass is 7.3%. The average improvement in the deformation modulus after grouting is 13.5%. After grouting, the permeability of 99% of the inspection holes in the Lugeon test section had Lugeon values of no more than 3 LU. This improvement is considerable and provides a case to engineering application.

Influence of operation time, hydraulic load and drying on phosphate retention capacity of mineral filters treating natural swimming pool water

Three parallel mineral filters, each with a volume of 2550 cm3, were used for phosphate removal from natural swimming pool (NSP) water. Filters worked continuously in saturated conditions. Hydraulic loading rates (HLRs) were 15 m3/m2h, 15 m3/m2d and 5 m3/m2d for Filter 1 (F1), Filter 2 (F2) and Filter 3 (F3), respectively. In the middle of the length of the filter, an inspection hole was located for sampling the filtration material. Samples were collected on the 55th, 87th and 120th day of filter operation. The phosphate sorption capacity of materials sampled from the filters was significantly lower than the sorption capacity of the fresh material, with their values varying between filters (different HLRs) and sampling events. In the case of F3 (slow filter), a decreasing phosphate sorption capacity was observed along with the time of operation. However, filtration material sampled from filters F1 and F2 had a higher P sorption capacity at the end of the monitoring period (day 120th day) than at the time of second sampling (day 87th day). This may suggest that the biofilm which developed on the grains of the filter blocked the contact between reactive material (RM) and treated water. Breaking the biofilm due to a faster flow (F1 and F2) resulted in increased filter sorption capacity. The remaining material sampled from F1, F2 and F3 was dried and also tested for P sorption capacity. Results showed that air drying increased the P sorption capacity of material from below 50% up to 100% of initial value, which suggests that periodic drying of filters may be a simple option for the regeneration of filtration material. P-bounded forms in filters were also analysed and discussed.

Videoscope-based inspection of turbofan engine blades using convolutional neural networks and image processing

A typical aircraft engine consists of fans, compressors, turbines, and so on, and each is made of multiple layers of blades. Discovering the site of damages among the large number of blades during aircraft engine maintenance is quite important. However, it is impossible to look directly into the engine unless it is disassembled. For this reason, optical equipment such as a videoscope is used to visually inspect the blades of an engine through inspection holes. The videoscope inspection method has some obvious drawbacks such as the long-time attention on microscopic video feed and high labor intensity. In this research, we developed a damage recognition algorithm using convolutional neural networks and some image-processing techniques related to feature point extraction and matching in order to improve the videoscope inspection method. The image-processing techniques were mainly used for the preprocessing of the videoscope images, from which a suspected damaged region is selected after the preprocessing. The suspected region is finally classified as damaged or normal by the pre-trained convolutional neural networks. We trained the convolutional neural networks 2000 times by using data from 380 images and calculated the classification accuracy using data from 40 images. After repeating the above procedure 50 times with the data randomly divided into training and test groups, an average classification accuracy of 95.2% for each image and a damage detectability of 100% in video were obtained. For verification of the proposed approach, the convolutional neural network part was compared with the traditional neural network, and the preprocessing was compared with the region proposal network of the faster region–based convolutional neural networks. In addition, we developed a platform based on the developed damage recognition algorithm and conducted field tests with a videoscope for a real engine. The damage detection AI platform was successfully applied to the inspection video probed in an in-service engine.

Numerical simulation and measurement analysis of the temperature field of artificial freezing shaft sinking in Cretaceous strata

Targeting the challenging analysis of the temperature field of the artificial freezing shaft sinking projects in Cretaceous strata, this study used the Hongqinghe air shaft freezing project as an example to perform a numerical simulation and measurement analysis of the temperature field of shaft sinking via the artificial freezing method in Cretaceous strata. First, the thermal physical parameters and mechanical properties of frozen Cretaceous rock were measured in the lab. Based on the engineering geological conditions and test parameters, the Hongqinghe air shaft freezing parameters were designed, and the preliminary scheme of the freezing project was obtained, in which a single ring of freezing holes was arranged in Cretaceous strata, the freezing wall had a design thickness of 3.7 m, and the average temperature was -12°C. Next, a numerical model for the temperature field of the freezing project was established to predict and analyze the effective thickness, average temperature, and shaft wall temperature of the frozen wall at different depths of shaft excavation. Finally, a comparison and analysis of field temperatures measured at the inspection holes and shaft walls showed that the numerical simulation results generally agreed with the field measurements. The field measurements showed that at the initial stage of freezing, the cooling rates of fine-, medium- and coarse-grained sandstones were 0.364 °C/d, 0.397 °C/d and 0.440 °C/d, respectively. Informatized construction enabled the air shaft freezing project in the Hongqinghe coal mine to be completed successfully.

Study on Technology of Surface Pre-grouting for Vertical Shaft in Broken and Water-rich Granite Strata of Gaoligong Mountain Tunnel of Dali-Ruili Railway

The Gaoligong Mountain Tunnel of Dali-Ruili Railway is located between the Nujiang River and the Longling County Town in the southeastern section of the Hengduan Mountains, China. In geological history, this area was affected by multiple tectonic movements, and the faulted structures are extremely developed. During the drilling inspection hole of No.2 vertical shaft, boring tool stuck and the hole collapse once happened. Its depth was 643.12 m, the outcropped strata were all granite or weathered granite (fracture zones). 7 fracture zones with thickness > 10 m were uncovered, the maximum thickness of which was 112.95 m; and 7 water bearing strata were uncovered, of which the buried depth of groundwater table was all less than 34m, the permeability coefficients(k) were 0.005∼0.158 m/d. It was estimated that the water inflow of ④ ∼ ⑦ aquifers of the main shaft and the auxiliary shaft of No. 2 shaft were all greater than 120 m3/d (5 m3/h), that normal water inflow of main shaft and auxiliary shaft of No.2 vertical shaft would be 125.92 m3/h and 90.08 m3/h respectively. In order to avoid water inrush and wall caving accidents during the construction of the two shafts, it was decided to adopt the surface pre-grouting method in the construction of the shafts to block off and reinforce the ④ aquifer and the strata under the aquifer. The “S” shaped directional drilling technology was used; the two sequences, segmented downward, multiple-times grouting mode was adopted; clay-cement slurry was selected as the grouting material. After grouting, pump yield water tests were carried out in two grouting holes of main shaft and auxiliary shaft. The remaining water inflow in grouting sections of two shafts was 5.02 m3/h and 5.70 m3/h respectively, and the rates of water blocking were all over 93%. The grouting effect was remarkable. The successful implementation of the surface pre-grouting project of No.2 vertical shaft in Gaoligong Mountain Tunnel of Dali-Ruili Railway has important guiding significance for the design and construction of tunnel and mine shafts in broken water-rich granite stratum.

Load-Carrying Capacity of End Cross-Girder with Inspection Holes in Composite Bridge

A severely corroded end cross-girder is found occasionally, while the girder is expected to play an important role under seismic loading. The prevention of the end cross-girder against corrosion is therefore crucial in the bridge maintenance. To this end, the present research aims at improving its inspectability by installing inspection holes in the end cross-girder. The influences of the holes on the load-carrying capacity are then studied, to be specific. It is revealed that the inspection holes would reduce the load-carrying capacity considerably; the degree of the influence varies with the shape, the position and the size of the hole. Six reinforcement methods are therefore considered. Full recovery of the capacity turns out to be possible if the inspection hole is the same size as that of the standard opening (manhole) in a steel bridge structure, while it is not an easy task when the inspection hole is larger.

Formation Mechanism of Inclusion Defects in Large Forged Pieces

Nonmetallic inclusions mixed into large forged metal objects destroy the continuity in the metal and affect the quality of the forged product. Research on how inclusions affect the plastic deformation of a matrix shows the significance of the formation mechanism of inclusion defects. For upset forging, the nonlinear finite element model was shown to be appropriate for the ingot hot-forging process by comparing the results with experiments involving plastic and hard inclusions inserted into the forged piece. The high-temperature stress-strain curves of MnS plastic inclusions were obtained experimentally. The results show how, during upsetting, the morphology of MnS plastic inclusions varies from spherical to ellipsoidal, until finally becoming flat in shape. The larger the inclusion is, the larger the degree of deformation of the inclusion is, and large inclusions enhance the risk of the final product failing to pass inspection for inclusion flaws. Strain significantly concentrates in the matrix near a hard inclusion. When the hard inclusion reaches a certain size, conical fractures form on both sides of the inclusion. To pass inclusion-flaw inspection and close hole defects to the extent possible, the flat-anvil upsetting is recommended. Finally, the inclusion-deformation state obtained by finite element simulation is verified experimentally.

Numerical Simulation of Forming Process for Cover with Stiffening Components Made of Grade 2 Titanium Sheet Metal

This study presents the findings of numerical simulations of forming process for an inspection hole cover with stiffening ribs made of thin grade 2 titanium sheet metal. The numerical simulation was carried out using the FEM method with PAMStamp 2G software. Numerical calculations were performed with consideration for the phenomenon of material strain hardening and anisotropy of plastic properties of the sheet metal formed. Properties of the grade 2 titanium alloy analysed in the simulations were adopted based on the results of the empirical studies. Adequate parameters of the forming process were selected in order to eliminate unfavourable phenomena of losing of material coherence and sheet metal wrinkling. The effect of conditions of friction between the sheet metal and tool and pressure force of the blank holder on the forming process was investigated. The analysis of the distribution of plastic strain and reduction in wall thickness of the drawn parts can be used for determination of the effect of changes in selected parameters and orientation of the specimen on the process of drawn part forming. The quality of drawn parts was assessed based on the shape inaccuracy determined during simulation of forming. The inaccuracy depended on the conditions of the process and strength properties of the titanium sheet metal.

Effect of Inspection Holes on Flexural Properties of Douglas-Fir Utility Poles

Abstract Routine inspection of wood utility poles to detect internal decay involves drilling holes at or about the ground line. While these holes are useful for detecting internal decay, their presence raises concern among engineers about their potential effects on pole flexural properties. The effect of inspection holes on flexural properties was studied on 92 Douglas-fir poles. Drilling up to six 20-mm-diameter inspection holes had no significant effect on flexural properties, indicating that inspection does not adversely affect pole condition.

구조안전성 기반의 가로등주 설계개선방안

The road luminaires have been treated as subsidiary electric apparatuses in the road although they are indispensable facilities which people use the road safely. Because of this misunderstanding, there are not many researches on luminaire supports against the wind loads. Therefore, a typhoon has overturned or damaged many luminaire supports without having sufficient structural safeties. The purpose of this study is to review the current design criteria and to suggest the improvement of design methods based on the structural safety and compatible with the site conditions of luminaire supports. The stress concentration around the inspection hole, which causes the collapse of luminaire supports, is analyzed and stress reduction method is suggested with the improved design methods.

New Electromagnetic Imaging Tool Introduced for Corrosion Detection

The new Electromagnetic Imaging Tool (EMIT) is introduced in this study. It is also described that the basic inspection theory, system structure and applications. The EMIT can determine whether metal loss or casing damage has occurred internally or externally. A 3D casing image can be supplied, including horizontal, vertical profile. The experimental results show that the EMIT has a “high-resolution” for MFL method in the casing well because of the steel brush structure. The minimal diameter of the inspection hole is 4 mm, and the thickness determination error of casing wall is 0.4 mm. A number of examples from oilfield are presented.

Defects Diagnosis Technology of Water Supply Pipe's Network Using Pipe Endoscope Camera of High Resolution/High Pressure Resistance Performance

The size of pipe network accident caused by aging of water distribution system, rapid urbanization, abnormal climate or a disaster such as an earthquake is gradually becoming larger. Accordingly, it is required to improve the technology to maintain the water distribution system so that the related technologies can be scientifically and systematically applied. The paradigm of Korean water supply service is changing from supply era to maintenance era, and it is required to apply equipment and method to effectively check, diagnose and test the internal condition of the pipe without stopping water supply. If photographing and diagnosis of the burial environment around the water service pipeline and inside the pipe can be carried out without stopping water supply effectively utilizing the surrounding facilities such as straight piping and air valve to the maximum, decrepit pipe (defective pipe) improvement projects can be effectively carried out by making adequate decisions. Also, a systematic and more efficient water supply service maintenance system can be established by building a database of surrounding pipeline directly investigated and selecting priority of direct/indirect evaluation. This study has raised accuracy of a diagnosis by applying a camera capable of securing high resolution without generation of distortion in case of photographing the inside of a pipe, and suggested an application method of the pipe endoscope camera using an inspection hole inside a pipe.