Trenching Process Research Articles

基于 EDEM 仿真与土槽试验的移动式开沟器土壤扰动规律研究

The mechanism of furrow opener-soil interaction plays an important role in analyzing the process of no-till planting furrow opener. In order to study the disturbance effect of the furrow opener on the loam soil, firstly, the three-dimensional model of the furrow opener was established by using SolidWorks. Secondly, the 3D discrete element model of furrow opener-soil interaction was established by EDEM software. Combined with the indoor soil bin test bench and high-speed camera technology, the micro-disturbance and macro-disturbance behavior of the furrow opener on soil at different positions, speeds and operating depths were compared and analyzed. The results showed that, the disturbance range of soil was decreased with the increase of the distance between the furrow opener and the soil. At different locations, the disturbance range of soil from large to small was the surface layer, the shallow layer and the middle layer. Under the conditions of three different layouts of furrow openers, through the comparison of the soil trench test and the simulation test, it was determined that the furrow openers in a staggered layout would be beneficial to reduce the degree of soil disturbance. In the trenching process, the soil movement velocity was decreased with the increase of the distance between the soil and the furrow opener, and the distribution curves of the same-speed soil particles were basically consistent with the curves of the furrow opener. The average velocities of soil particles with different velocities and depths in different directions were the surface layer, the shallow layer and the middle layer. However, there were differences in the maximum velocities of soil particles in different directions. By comparing the data obtained from the simulation test and the soil bin test, it was found that the parameters obtained from the simulation and the test were basically consistent, and it was determined that the discrete element simulation could simulate the soil disturbance behavior of the furrow opener more accurately. The relative errors of cross-sectional area of the front furrow opener and the rear furrow opener were 2.48 % and 5.2 %, respectively. The relative errors of the dynamic soil rate of the front furrow opener and the rear furrow opener were 0.25 % and 5.12 %, respectively.

Energy saving and environment protection solution for the submarine pipelines based on deep learning technology

Underwater flowlines (pipelines and cables) have become a popular option worldwide as communication lines. Correspondingly the demand for underwater trenching increased with the most desirable method internationally, jet trenching for its benefits in protecting the flowlines from external hazards. However, the trenching method is suffering from a main problem that can affect the construction and operation phases. This problem is the use of maximum jetting pressure needed for underwater trenching which leads to extra costs in the construction phase. Furthermore, the unstraightening of the trench can cause extra stress on the flowline requiring extra maintenance in the operation phase. The key cause of this problem is the classification of the underwater soil, as if the underwater soils cannot be classified as accurately as possible, the suitable jetting pressure required to trench these soils could not be applied correctly. Therefore, this research aims to develop a machine learning classifier for soil classification as a solution for enhancing the performance of the underwater trenching process. This classifier was constructed, trained, and evaluated by MATLAB R2020a to classify the underwater soil type by analyzing the soil image samples by an artificial neural network (ANN). Then a prototype that mimics exactly the real trenching mechanism was built to test the developed classifier based on three different types of soil (sand, clay & gravel). The results showed that the classifier successfully identify and classify the three different types of soil used. Finally, the results confirmed that the classifier will enhance the trenching processes. As it eliminates the need for soil classification by conventional methods while executing it in an easy fast process that will save energy, and cost, and decrease the need for future maintenance processes.

The Role of Cu-Based Intermetallic on the Direct Growth of a ZnAl LDH Film on AA2024

The direct ZnAl layered double hydroxide growth on AA2024 is a fast-occurring reaction, yet is characterized by an inhomogeneous film thickness. It has been shown that at the periphery of Cu-rich intermetallic, the flakes tend to be larger and denser. A combination of in situ and ex situ measurements were used to monitor the changes in the layered double hydroxide film grown on the regions of intermetallics. Immediately after immersion, an activation of the intermetallic phases is observed due to the dealloying process with an almost immediate film growth. Dealloying is followed by trenching of the adjacent Al matrix leading to an excessive production of large and dense layered double hydroxide flakes at the periphery of the intermetallic. However, the scanning electron microscopy cross-section images revealed that the trenching process leads to defects in the area surrounding the intermetallic. This could weaken the corrosion resistance performance of the layered double hydroxide conversion coating and lead to adhesion failure of consecutive polymer coatings. Nevertheless, this work highlights a few advantages and drawbacks of the layered double hydroxide conversion coatings and pathways to its potential optimization and improvement.

A FEM model for simulating trenching process around a MnS inclusion embedded in stainless steel

A finite element method model has been elaborated to study the localized corrosion around a MnS inclusion particle in stainless steel, taking into account the three electrochemically active phases of the matrix, passive film and MnS inclusion. The simulation results show the evolution of this micro-galvanic corrosion process, which is initiated by MnS dissolution, followed by the simultaneous dissolution of the inclusion and matrix, and finally, the MnS inclusion stops dissolving and turns to be cathodic, leaving the matrix as the only corroding phase (“trenching” process). The deposition kinetics of the corrosion products and pH distribution around the corroding area are also predicted.

十字槽开沟器横刀后掠角对土壤扰动的影响

The cross-slot opener is a new type of seeding opener. The sweep angle, which is a key structural parameter of the cross knife, has an important influence on soil disturbance. In this paper, discrete element method and tracer method are used to study the conditions of working speed of 0.83m/s and ditching depth of 130mm, the sweep angles of the transverse knife are 0°, 10°, 20°, 30°, 40°, respectively. The influence of time opener on soil disturbance and working resistance. The simulation analysis of the operation process of the cross groove opener shows that the trenching process under different sweep angles of the transverse knife is basically the same, and the standing knife is the main cause of soil disturbance; both the tracer method and the simulation results show the surface and shallow soil particle disturbance. The proportional and horizontal working resistance first decrease and then increase with the increase of the sweep angle of the cross-slot opener. When the sweep angle of the cross-slot opener is 20°, the micro-disturbance of soil particles and the horizontal work resistance are the least; The relative error of the soil disturbance ratio obtained by the tracer method and the discrete element method are both within 15%, and the relative error of the horizontal working resistance is 6.5%. The established discrete element simulation model can more accurately simulate the soil disturbance process of the cross-slot opener.

Investigation of Rebar Exposure Issues of Diaphragm Wall and Influencing Factors Analysis

The exposure of rebar in diaphragm wall was discovered after excavation in more than 20 subway stations, along the lines 1 to 4 in Suzhou, China. Such phenomena were investigated from strata formation, hydrogeological condition, construction techniques, adjacent surcharge load and other aspects. Based on field investigation, in situ testing and numerical simulation, the disturbance of trenching operations and the main factors that affect the stability of the diaphragm wall during the trenching process are analyzed comprehensively. The results show that the deformation behavior and stability of slurry trench walls are mainly influenced by strata characteristics, adjacent surcharge loading, formation of bentonite filter cake on trench walls, pressure of a confined aquifer, height of slurry filling and slurry density. The underground water pressure in the confined aquifer of silty soil layers is considered as one of the main controlling factors, which is verified by the subsequently dewatering and trenching tests. During the construction process, the deformation and stability of the trench walls can be improved by adjusting and controlling the crucial controlling factors. Further, relevant remedial measures as well as the preventive methods during the process of constructing diaphragm walls and subsequent soil excavation are addressed.

Embedded Metal Microstructures in Glass Substrates by a Combined Laser Trenching and Printing Process

Embedded Metal Microstructures in Glass Substrates by a Combined Laser Trenching and Printing Process

The influence of trenching diaphragm wall panels on deflection and bending moment of existing piles within piled foundation

Conducting deep excavations for underground construction inside the cities requires diaphragm wall due to space limitation. The ground surface is affected by the trenching process. The construction of the diaphragm walls near deep foundations may not be avoided specially in the crowded cities. This research focuses on the deflection and bending moment of piled foundations near slurry trench. Since the trench is considered as a three-dimensional problem, a three-dimensional numerical analysis was used in this research. It was conducted using a commercial analysis software known as FLAC 3D. The numerical analysis method was verified using two case histories, one in Hong Kong and another one in Giza, Egypt. The results from the numerical analysis were in quite a good contrast with the field data results. This indicates that the trenching process could be numerically modeled with the proposed method and provides good results. The verified numerical analysis method was used to conduct a numerical parametric sric study that discusses the effect of multiple panels on adjacent connected pile groups or piled raft foundation. The parametric study showed that the pile deflection and bending moment are affected by the panel construction stages, pile location within the foundation. The pile deflection and bending moment are affected by the stages of construction. The piles near the trench are affected by the trenching process, while the piles far from the trench are affected by the dragging force of the pile near the trench.

MPM Simulations of the Interaction Between Water Jet and Soil Bed

In offshore engineering, pipelines are often buried in the seabed to avoid the damage caused by ocean waves, currents, fishing activities, etc. For its reliability, the high-speed water jet has been increasingly used for constructing the pipe trenches. The jet-soil interaction is a highly complicated two-phase problem. A three-dimensional Material Point Method (MPM) model, Anura3D (www.anura3d.com), is used to simulate the jet trenching processes. In this preliminary study, the effect of the water jet speed on the trenching process is simulated. The research demonstrates the advantages of the MPM model in handling the free surface and soil-water interaction problems, and the results are useful for the offshore oil and gas industry. In future research, the different controlling parameters of the trenching operation, including the jet size, water pressure, translational speed and soil strength, will be tested to optimize the trenching operation to achieve high efficiency.

Tractive performance evaluation of seafloor tracked trencher based on laboratory mechanical measurements

To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model). To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture), was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.

Effect of Groundwater Table Rising and Slurry Reduction during Diaphragm Wall Trenching on Stability of Adjacent Piles

The process of diaphragm wall trenching normally affects the surrounding environment. The piles near a diaphragm wall trench are commonly affected by the trenching process as well. During trenching the slurry level and the natural groundwater level are assumed to be constant. However flooding may cause damage to the slurry trenches due to the increase of the groundwater table. Another possible scenario for the trench failure is due to reduction of the slurry level. The reduction of the slurry level could be due to the presence of cavities or a very coarse soil layer. Piles located near a trench could be affected greatly if the trench is subjected to reduction of slurry or increase of the groundwater level. This research focuses on studying numerically the stability of piles adjacent to the diaphragm wall during the trenching process, especially in cause of slurry reduction or increase of groundwater level. The slurry reduction were simulated numerically with the finite different analysis and compared with previous laboratory work. The increase of groundwater level is simulated for a case study in Giza, Egypt. Groundwater level was assumed to increase in the area. Piles are generally affected by the trenching process. The behaviour of the pile is related to its position from the slurry trench. The stability of the pile may not be affected greatly by a normal and successful trenching process. However slurry reduction or increase in the groundwater level may cause a great effect on the stability of the nearby piles. Trenching in general causes an increase in pile settlement, horizontal displacement and bending moment. The pile skin friction and end bearing are affected as well. The percentage of the change in slurry or groundwater levels affects piles deflection and bending moment.

Construction Techniques of Deep Diaphragm Wall in the Yellow River-Crossing Project in South-to-North Water Transfer

Yellow River-Crossing Project in South-to-North Water Transfer approach through the use of shield tunnel and its north bank departure shaft adopts diaphragm wall as enclosure structure. The depth of continuous wall of its shielding starting shaft is 76.6m, which is the deepest at present in china. The continuous diaphragm wall travels through the layer of silver sand, medium sand and loam from top to bottom, where the geological conditions are poor with large difficulty of construction. This paper sets forth construction of guide wall, reinforcing measures before construction, Trenching process, groove segment connections, innovative technologies of uplifting huge reinforcing cage and so on, which will provide guidance and lessons for the similar project

The development of montane arroyos and gullies

Field investigations in the Front Range of Colorado, U.S.A., confirm that the spatial distribution of vegetation in watersheds exerts strong control on the entrenchment of streams in the montane zone. When tractive force in channels exceeds threshold values of resistance on the valley floors, cutting of arroyos begins, producing forms that change allometrically. An algorithm based on the Cooke Method for discharge, the Manning Equation for depth of flow, and the DuBoys Equation for tractive force can be used to evaluate force for observed and experimental conditions. In small (<5 km2) basins in the Front Range of Colorado, forces for the 10-year discharge commonly range from 1 to 5 dynes, but the resistance offered by valley floors is usually unable to withstand forces from channel flows greater than 2 dynes. Biomass of vegetation on the valley floor exerts significant control on the trenching process, with threshold values of biomass commonly between 1.5 and 9 kg/m2, the range of semi-arid vegetation cover. Thresholds exist in the montane erosion system for gradient, mean biomass in the basin, biomass on the valley floor, channel roughness, and channel width. Each threshold value, however, depends on the interrelationships among other variables in the system. Manipulation of the vegetation cover is the primary human impact on the montane channels, and management of the distribution of vegetation offers the most efficient method of maintaining the stability of channels.

Aeronautical research laboratory

To evaluate the tractive performance of tracked trencher on seafloor surface, a new shear stress-displacement empirical model was proposed for saturated soft-plastic soil (SSP model). To validate the SSP model, a test platform, where track segment shear test can be performed in seafloor soil simulacrum (bentonite water mixture), was built. Series shear tests were carried out. Test results indicate that the SSP model can describe the mechanical behavior of track segment with good approximation in seafloor soil simulacrum. Through analyzing the main external forces applied to seafloor tracked trencher during the uniform linear trenching process, a drawbar pull prediction model was deduced with the SSP model. A tracked walking mechanism of the seafloor tracked trencher prototype was built, and verification tests were carried out. Test results indicate that this prediction model was feasible and effective; moreover, from another side, this conclusion also proved that the SSP model was effective.