Maximum Inclination Research Articles

On the seafloor horizontal displacement from cGPS and compass data in the Campi Flegrei caldera

Seafloor deformation monitoring is now routinely performed in the marine sector of the Campi Flegrei volcanic area (Southern Italy). The MEDUSA infrastructure is formed by four buoys deployed at a water depth ranging from 40 to 96 m, and equipped with cGPS receivers, accelerometers and magnetic compasses to monitor the buoy status and a seafloor module with a bottom pressure recorder and other onboard instruments. The analysis of the time series data acquired by the MEDUSA monitoring infrastructure system allows to study the seafloor deformation in the Campi Flegrei caldera with geodetic accuracy. In a previous work, we show that the time series acquired by the Campi Flegrei cGPS onland network and MEDUSA over the period 2017–2020 are in good agreement with the ground deformation field predicted by a Mogi model which is widely used to describe the observed deformation of an active volcano in terms of magma intrusion. Only for one of the buoys, CFBA (A), the data differ significantly from the model prediction, at a level of simeq 6.9 sigma and of simeq 23.7 sigma for the seafloor horizontal speed and direction, respectively. For this reason, we devised a new method to reconstruct the horizontal sea bottom displacement considering in the analysis both cGPS and compass data. The method, applied to the CFBA buoy measurements and validated also on the CFBC (C) buoy, uses compass data to correct cGPS positions accounting for the pole inclination. Including also systematic errors, the internal consistency, always within sim 3 sigma for the speed and sim 2 sigma for the angle, between the results derived for different maximum inclinations of the buoy pole (up to 3.5^{circ }) indicates that the method allows to significantly reduce the impact of the pole inclination which, if not properly taken into account, can alter the estimation of the horizontal seafloor deformation. In particular, we find a good convergence of the retrieved velocity and deformation angle as we include in the analysis data from increasing values of the buoy pole inclination. Taking the result derived assuming the maximum allowed cutoff and accounting for statistical and systematic errors, we found a speed v = (3.521 ± 0.039 (stat) ± 0.352 (syst)) cm/yr and a deformation direction angle alpha = (-115.159 ± 0.670 (stat) ± 7.630 (syst))^{circ } (statistical errors at 1 sigma quoted from the rms of their values, main systematic errors added linearly). The relative impact of the main potential systematic (statistical) effects increases (decreases) with the cutoff. Our analysis provides a horizontal speed consistent with the model at a level of simeq 5.2 sigma (stat only) or of simeq 0.5 sigma (stat and syst added linearly), and a deformation angle consistent with the model at simeq 4.3 sigma level (stat only) or at simeq 0.3 sigma level (stat and syst added linearly). Correspondingly, the module of the vectorial difference between the velocity retrieved from the data and the velocity of the adopted Mogi model diminishes by a factor of simeq 7.65 ± 1.23 (stat) or ± 5.78 (stat + syst) with respect to the previous work. A list of potential improvements to be implemented in the system and instruments is also discussed.

ST-segment elevation myocardial infarction and the clinical significance of differentiated electrocardiogram

Aim. To evaluate the markers of changing dynamics recorded by digital processing of routine ECG using own diagnostic complex software “Smart-ECG” in patients with ST-segment elevation myocardial infarction (STEMI) based on the results of a 40-day follow-up. Materials and methods. The main group consisted of 20 patients with STEMI according to the ESC guidelines (2017) (mean age of males 56.11 ± 11.62, n = 10; mean age of females 58.22 ± 13.11, n = 10). ECG were analyzed using own developed diagnostic complex software “Smart-ECG” on the 1st, 10th, 40th day after STEMI. The first derivative of T wave – ratio of maximum velocity (MVR), inclination angle (β) and inclination height (H) of ST segment was calculated. The control group – 20 apparently healthy people. Results. MVR indicators decreased by 61.90 %, 68.20 % and 51.48 % on the 1st, 10th and 40th day, respectively, after STEMI as compared to those of the control group (p < 0.01). At the moment of the maximum ST segment elevation, the height (H) of ST inclination was 347.7 % increased (p < 0.01); on the 40th day, H was 25 % increased, close to control indicators, with ST segment shift to isoline (р > 0.05). During the acutest period, the angle β increased by 172.2 % (p < 0.01) and then decreased by 15.8 % at the recovery phase, but insignificantly. Conclusions. Self-developed medical software “Smart-ECG” for qualitative evaluation of ECG is an effective tool to diagnose pathological changes in the myocardium, makes it possible to improve the specificity, sensitivity and prognostic significance of ECG in STEMI. The significant decrease in MVR has been detected at all stages of STEMI, which was associated with a violation of electrogenesis in the repolarization phase; the critical increase in ST slope indicators (angle β and height H) on the 1st day has been found as a characteristic of ST elevation, as well as its decrease on the 40th day as a sign of reduced potential difference between healthy and damaged areas of the myocardium during the recovery stage.

Mechanical Properties of Sheet Pile Cofferdam during Adjacent Open Cut Tunnel Construction near Lake Bottom

In water-related projects, the application of steel sheet pile cofferdams is becoming more and more widespread, and the influence of tunnel construction on the mechanical properties of adjacent cofferdams is important. In this study, the object of research was the mechanical properties of large-span steel sheet pile cofferdams. The open-cut tunnel project was located in Suzhou Yinshan Lake, China. According to the actual construction steps of the tunnel foundation pit, assuming that the soil was a small strain hardening soil model, combined with on-site monitoring data, a three-dimensional elastoplastic finite difference model was established. The results show that during tunnel construction, the maximum settlement of the cofferdam appeared at 0.27~0.53 m on the side of the foundation pit; the maximum horizontal displacement of the steel sheet pile occurred at the pile bottom of foundation pit side, and the seepage gradually increased during construction, eventually resulting in water gushing at the bottom of the foundation pit. After the completion of tunnel construction, the settlement value of the cofferdam presented a pattern that first increased and then decreased from the side of the foundation pit to the side of the adjacent lakeside; the steel cofferdam tilted toward the side of the foundation pit, with a maximum inclination angle of 3.37°. It should be pointed out that as the construction progressed, the axial force of the tie rods in the steel cofferdam changed from a U-shaped distribution to a V-shaped distribution. This study could provide a reference for the impact of tunnel foundation pit construction on adjacent steel cofferdam and could also provide a reference for the safety research of open-cut tunnel construction.

A New Approach for Structural Monitoring Based on Terrestrial Laser Scan Data Using Control Planes

Laser scanning is a survey method that enables the obtaining of several data points on surfaces through the observation of horizontal and vertical angles and electronic distance measurements. The result of these observations is a set of 3D points named point clouds, which can be obtained from scans using total stations or the Terrestrial Laser Scanner (TLS). Currently, the use of TLS in geodetic structural deformation monitoring activities is under evaluation, since this technique can provide a greater number of points in a shorter period, when compared to scans performed by total stations. In this research, the feasibility of using control planes for geodetic monitoring was investigated in a controlled laboratory environment, exploring the current trend of parameterization of point clouds. From the development of an Experimental Plane Control (EPC) containing a flat surface that could be inclined in a controlled way, simultaneous scans with TLS and total station were carried out at different inclinations of the control plane. Both surveys were done in frontal scan mode (minimum plane inclination of 0º53’ and maximum plane inclination of 3º28’) and in oblique mode (plane inclination of 1º09’), where the plane inclination angles were generated by the rotation in EPC base, considering the first plane position as reference to inclination calculating. From parametrization of point clouds, a new approach was developed to test the significance of the estimated inclination angle of the plane in relation to a reference position. The results showed that it is possible to confirm that the inclined angles were statistically significant, but that the TLS scanning position can interfere in the determination of these data for monitoring purposes.

C1 anatomy and dimensions relative to pedicle screw placement

The recent C1 pedicle screw technique for upper cervical vertebral stabilization allows longer screws to be implanted by setting the screw entry point through the posterior arch of C1, which could provide better biomechanics. However, there is controversy regarding the placement of C1 pedicle screws at different angles. We retrospectively reviewed the computed tomography (CT) scans of 300 patients. The trajectories of medial inclination of 0°, 5°, 10°, and 15° and trajectory of the maximum medial inclination angle were designed for each C1 pedicle on CT images. Screw track length at each angle, the angle of maximum medial inclination, pedicle height, distance from the screw entry point to the midpoint of the C1 posterior tubercle, and screw perforation rate at each angle were measured. The average maximum inclination angle was 17.01°, the maximum inclination angle screw track length was 31.05 mm, and the distance from the screw entry point to the midpoint of the C1 posterior nodule was 21.65 mm. The screw perforation rate was 46.73% at 15° of medial inclination, but only 5.61% at 10°, and no screw perforation at 5°. 26.47% C1 pedicle height < 4 mm. There was no significant difference between the measured data on the left and right sides(P > 0.05), and the measurement of female patients was usually smaller and significantly different from that of male patients(p < 0.05). Our data indicate that a reasonable screw inclination angle of 10° and the safety zone of screw angle can provide safety and avoid screw perforation. However, personalized measurement before surgery is essential.

Full-Scale investigation on inclined ballastless cant track using concrete slab panel at high temperature setting

The topography condition in the mountainous region has limited the construction of high-speed railways. Therefore, the proposed research aims to develop a new cant track model which is designed at a maximum inclination of 180 mm to simulate the curved sections on these highland areas. This construction methodology incorporates the advantages of the strong stress-bearing property of concrete slab panels and the robust stress distribution ability of the asphalt concrete trackbed. The installment of concrete slab and optimized asphalt concrete mixture were also used to counter the negative impact of the high temperature during summer in South Korea on the asphalt concrete layer. In this research, the performance of the cant track system was analyzed by using the Rail Load System built by the Korea Railroad Institute. There are two featured loading stages including the static load and cyclic load. The static load was designed in the loading and unloading process between 0 and 210kN with an amplitude of 30kN. Concerning the dynamic behavior on the testbed section, 3 million cyclic train loads were applied at a frequency of 7 Hz to simulate the train speed of 350 km/h. The thermal air blow system was installed surrounding the cant track to keep the temperature at the core asphalt concrete at a constant value. Overall, the full-scale testbed results confirm the positive applicability of the cant track since stress can be homogenously distributed along the track substructure. Moreover, the rail plastic displacement and tensile strain of asphalt concrete roadbed were noticeably reduced compared to the conventional long sleeper ballastless track.

Steep freeform measurement method based on a normal transverse differential confocal.

A normal transverse laser differential confocal freeform measurement (NTDCFM) method was proposed to address the high-precision measurement difficulty of steep freeform surfaces with large variations in inclination, scattering, and reflectance. Using D-shaped diaphragm technology, the freeform surface under test (FSUT) axial variation transformed into a spot transverse movement on the detection focal plane. Meanwhile, a 2D position sensitive detector (PSD) was used to obtain the normal vector of the sampling points so that the measuring sensor's optical axis could track the FSUT normal direction. The focus tracking method extended the sensor measurement range. Theoretical analysis and experimental results showed that the axial resolution of the NTDCFM was better than 0.5 nm, the direction resolution of the normal vector was 0.1°, the maximum surface inclination could be measured up to 90°, the sensor range was 5 mm, and the measurement repeatability of the FSUT was better than 9 nm. It provides an effective new anti-inclination, anti-scattering, and anti-reflectivity method for accurately measuring steep freeform surfaces.

Prediction of the lateral stability of a forestry chassis with an articulated body and fitted with luffing wheel-legs

Due to the roads in forest being short of structured terrain, lateral stability of chassis is crucial for forestry vehicles. A forestry chassis with a novel articulated body and fitted luffing wheel-legs (AB + LWL) is proposed in this paper. The novel articulated body with three degrees of freedom which improves the ability to adapt to terrain is described. In particular, a luffing wheel-leg which enhances the lateral stability to run in forestry terrain, is proposed. After performing a detailed theoretical analysis of the mechanism equivalent, a new accurate the lateral stability model for the without driven luffing wheel-legs is derived. The new model predicts the lateral stability by analysis tyre contact forces, which is different from most models established by the geometrical position of centre of gravity. Significantly, a lateral stability model for an articulated body with driven luffing wheel-legs is derived. To verify the theoretical analysis, simulations that describe the lateral rollover for the chassis are established in ADAMS. The simulation is considered into two conditions, without driven luffing wheel-legs and with driven luffing wheel-legs. For the chassis without driven luffing wheel-legs, the lateral rollover is caused by the rear up-slope wheel when the inclination angle of slope reaches 34.8°. The maximum absolute percent difference of the rear up-slope wheel contact force with the theoretical analysis relative to the simulation is only 2.8%. For the chassis with driven wheel-legs, the lateral rollover which is also caused by the rear up-slope wheel will occur when the inclination angle of slope reaches 40.3°. The front or rear frame can be levelled by regulating the luffing wheel-legs when the inclination angle of slope is less than 15.29°. Compared with the chassis without driven luffing wheel-legs, the maximum inclination angle of slope increased 15.8%. The maximum absolute percent difference of the rear up-slope wheel contact force with the theoretical analysis relative to the simulation is only 1.6%. Simulation results validate the effectiveness of the proposed lateral stability models of the chassis in the two conditions. • Novel forestry chassis is proposed. • Lateral stability models not using geometric centre of gravity derived. • Simulations validated effectiveness of proposed lateral stability models. • New lateral stability models more accurate and more generic. • Articulated chassis with different active body control could be examined by models.

A magnetic soft robot with rolling and grasping capabilities

Soft robots offer a great application potential in the field of military, medical, and industry. In this study, a rolling gait was adopted to the design of the soft robot so as to improve the locomotion velocity of the soft robot actuated by the magnetic field. The soft robot was fabricated as a square frame structure (6 × 6 × 0.6 mm) to achieve grasping function. The experimental results indicated that the designed soft robot could roll on a slope with a maximum inclination around 30° under the given conditions. The velocity of the soft robot during the rolling process would decrease with the increase of the inclination. Meanwhile, the soft robot could carry objects 3.75 times its own weight when it rolled on a level pavement. Further analysis and experiments suggested that the rolling locomotion of the soft robot relied on the magnetic torque and the friction force. The locomotion velocity of the soft robot was related to the perimeter of the contour composed of the soft robot and the object being grasped. Moreover, a modular assembly strategy was proposed to improve the locomotion and grasping performance of the soft robot. The findings of this work will help to promote the application of untethered soft robots.

Structural Evaluation of the Effect of Bone Quality on the Mechanical Interaction between Dental Implants and Bone

When one or more teeth are lost for any reason such as accident, caries, and gum disease, they should be replaced with dentures. Researchers discovered that titanium successfully bonds to bone because of the development of osteoblasts on its rough surface. However, the success of dental implants depends on biological, mechanical, and chemical factors. Each of these factors is itself a function of different parameters that, any changes in these factors affect the mechanism of transfering from the prosthesis to the implant and from implant to bone. The role determinant in the success of implant therapy is the function of the geometry and mechanical properties of the implant, jaw and bone-implant joint. Now, due to the increasing use of dental implants, various companies are constantly launching their new products and, as a result, express many benefits of these products, which in most cases are based on their claims. It is not a long-term study, and therefore it is not possible to make an accurate judgment on the designs, macroscopic and microscopic properties, and benefits offered, due to the lack of accurate and practical comparisons between systems. It will not be possible to prove the effectiveness of each of them. Therefore, understanding the design method and its philosophy, along with familiarity with the types of systems available in the market, is a determining factor in the clinical success of dental implant treatment. The presence of threads prevents overload on the surface of the cortical bone and reduces this load by up to 36%. Reducing the thread pitch contributes to the stability of the implant, and increasing the depth of the thread stabilizes patients with poor bone quality. The behavior of the bone and its relation to the implant with regard to applied loads with a maximum inclination angle of 15° have been evaluated by evaluating the tension in the bony areas of the cortex and trabecular bone.

Adaptative Friction Shock Absorbers and Reverse Thrust for Fast Multirotor Landing on Inclined Surfaces

Small multirotors are not capable of landing in complex situations, such as on inclined surfaces, in wind gusts or at high impact velocities. This paper explores the use of lightweight friction shock absorbers, combined with rapid thrust reversal, to increase the landing envelope of a quadrotor. The friction shock absorbers serve to dissipate the drone’s kinetic energy and the reverse thrust increases the maximum slope inclination at which it can land. A landing gear prototype was designed and implemented on a DJI F450, and a model was created to generate landing maps to evaluate its benefits. Finally, the technology was tested in real outdoor conditions. The overall system enables drones to safely land on surfaces of up to 60° and at vertical speeds of up to 2.75 m/s, thus increasing the landing envelope by a factor of 8, compared to traditional multirotors.

Research on Foundation Deformation and Structural Stress Variation of Shaft Tower under the Influence of Frost Heave and Thaw Settlement

As the laws of structure deformation and structural stress variation under freezing construction around high-rise buildings are not clear and no engineering experience can be referred to, freezing method construction in this situation is paired with huge safety risks. In this paper, freezing construction was successfully carried out around the main shaft tower in Chensilou Coal Mine by taking the following protective measures: symmetrical drilling, local freezing and hot water circulation. The elevation of the shaft tower foundation is continuously measured during the process of drilling, frost heaving and thaw settlement (hereinafter referred to as the DHS process). Benefiting from these protective measures, the maximum inclination value (−0.406 mm/m) of the shaft tower is controlled at well below the allowable value. The observation data informed the settlement and inclination of the tower foundation during the DHS process. A numerical model of the shaft tower is further established based on the observation data to reveal the tower structure’s law of stress variation during the DHS process. In addition, the fitting equation between the tower inclination value and the structural stress is obtained, which can provide a reference for freezing construction of similar high-rise buildings.

Modeling and estimation of the optimal tilt angle, maximum incident solar radiation, and global radiation index of the photovoltaic system

This research was designed to apply measured and theoretically derived models to estimate the optimal tilt angle (β), maximum incident solar radiation (HT), and global radiation index (GRI) in Lagos and 37 metropolitan cities in Nigeria. Six modules were mounted at different tilt angles with two modules north-facing, three south-facing, and one positioned horizontally to determine the orientation and tilt angle performance. Overall, the 16.8° module 4 south-facing tilted emerged as the best performing module for HT, with maximum output power, and much more than 6.174 annual earned energy reported on module 6 mounted horizontally. The GRI obtained from the six solar modules revealed a significant coefficient of 1.0269 for module 1 north-facing, 0.9923 for module 2 north-facing, 1.0217 for module 3 south-facing, 0.9609 for module 4 south-facing, and 1.0232 for module 5 south-facing for the values obtained from the horizontally positioned module 6. In-depth statistical analysis of the effectiveness of values observed against the predicted values to estimate the optimal and maximum inclination angle of incident solar radiation using error metrics and GPI revealed that model 5, model 12, model 14, model 17, and model 14 outperform the other estimation models in their respective categories. A similar statistical analysis of model 14 with the best performance was performed to estimate the best inclination angle in 37 metropolitan cities in Nigeria compared to two models consolidated in the literature; model 14 performed admirably in terms of accuracy compared to the two models obtained from the literature.

Solid-State and Super Solidus Liquid Phase Sintering of 4340 Steel SLM Powders Shaped by Fused Filament Fabrication

4340 steel powders were processed with an additive manufacturing process using the FFF (Fused Filament Fabrication) technique. A composite filament was developed to print samples and study the effect of the bed and nozzle temperatures on its physical and microstructural properties. The printed samples were debinded and sintered by: Solid State (SS) at 1300 °C or SLPS (Supersolidus Liquid Phase Sintering) at 1420 °C. Metallography and scanning electron microscopy (SEM) identified the microstructure and phases. The hardness of the sintered samples was measured with the Vickers method. The SLPS process contributes to better densification and volume contraction; however, it promotes geometrical distortion of the samples compared to the SS samples. The microstructure of the sintered samples consists of ferrite situated in the original austenite grain and bainite. The sintering mechanism significantly influenced the hardness of the samples. Finally, a part was designed, printed, debinded, and sintered with the aim of studying the maximum inclination angle, the minimum vertical and horizontal holes, and the minimum vertical layer thickness, which can be obtained through the whole process.

Load Deformation Effect of CBD Ground Cluster in Zhengzhou City

With the increase of the number of urban cluster buildings, it is bound to cause land subsidence near cluster buildings. Based on Farrell’s load deformation theory, this paper studies the surface deformation and geoid change caused by Zhengzhou CBD cluster buildings. The results show that the maximum horizontal displacement of the International Convention and Exhibition Center is 0.1 mm, the maximum vertical displacement is 0.33 mm, and the maximum geoid fluctuation is 17.4 mm; the maximum inclination of geoid is 1.89 s. In addition, the influence of independent single buildings on ground deformation is centered on the single building and diffuses outward; the influence of cluster load buildings on the ground deformation of a single building is nonlinear attenuation and superimposed with each other.

Effects of Key Influencing Factors on the Flame Inclination of Low Concentration Methane (LCM) Combustion in Porous Burner

ABSTRACT In present work, a local thermal non-equilibrium numerical model of low concentration methane combustion in porous media is established. The modified thermal effective thermal conductivity of foam ceramics was introduced. The heat and mass dispersion effect as well as the influence of porous media structure on the heat transfer were fully considered. Studies found that the combustion flame front of low concentration methane in porous media always show a S-shaped state under special conditions. The influencing factors of inlet velocity, methane concentration, wall heat loss, and the porous burner size were analyzed. Results show that without initial thermal perturbation and the absence of defects in the porous media, the flame front in porous burner still has the possibility of inclination. As the inclination of the flame front continues to increase, the flame keeps approaching the burner outlet until blow off. Among the considered four influencing factors, the size of porous burner has the greatest influence on the inclination of flame front. As the burner diameter increases from 0.04 m to 0.12 m, the inclination angle of the flame front increases continuously, and the maximum inclination angle is 36°. The flame inclination will cause uneven temperature distribution downstream of the burner and local heat concentration. With the increase of wall heat loss, the high-temperature zone downstream of the burner will evolve into a local high-temperature zone near the flame front. With the reducing of porous burner diameter, the inclinational instability could be suppressed to some extent.

Optimal Pitwall Shapes to Increase Financial Return and Decrease Carbon Footprint of Open Pit Mines

The steepness of the slopes of an open pit mine has a substantial influence on the financial return of the mine. The paper proposes a novel design methodology where overall steeper pitwalls are employed without compromising the safety of the mine. In current design practice, pitwall profiles are often planar in cross-section within each rock layer; i.e., the profile inclination across each layer tends to be constant. Here instead, a new geotechnical software, OptimalSlope, is employed to determine optimal pitwall profiles of depth varying inclination. OptimalSlope seeks the solution of a mathematical optimization problem where the overall steepness of the pitwall, from crest to toe, is maximized for an assigned lithology, geotechnical properties, and factor of safety (FoS). Bench geometries (bench height, face inclination, minimum berm width) are imposed in the optimization as constraints which bind the maximum local inclination of the sought optimal profile together with any other constraints such as geological discontinuities that may influence slope failure. The obtained optimal profiles are always steeper than their planar counterparts (i.e., the planar profiles exhibiting the same FoS) up to 8° depending on rock type and severity of constraints on local inclinations. The design of a copper mine is first carried out employing planar pitwalls, secondly adopting the optimal pitwall profiles determined by OptimalSlope. The adoption of optimal slope profiles leads to a 34% higher net present value and reductions of carbon footprint and energy consumption of 0.17 Mt CO2 eq and 82.5 million MJ respectively due to a 15% reduction of rockwaste volume.

Stability Metric Based on Sensitivity Analysis Applied to Electrical Repowering System

Stability metrics are used to quantify a system’s ability to maintain equilibrium under disturbances. We did not identify the proposition of a stability metric using sensitivity analysis within the literature. This work proposes a system stability metric and its application to an electrical repowering system. The methodology for applying the proposed metric comprises: (i) system parameters sensitivity analysis and spider diagram construction, (ii) determining the array containing the line segments inclination angles of each spider diagram curve, and (iii) stability calculation using the array mean and maximum inclination value of a line segment. After simulating the model built for the electrical repowering system and applying the methodology, we obtain results regarding the sensitivity indices and stability values of system inputs relative to their outputs, considering the original system and with reduced parameters. Using the stability study, it was possible to determine different stability categories for the system parameters, which indicates the need for different analysis levels.

Experimental study on the migration and expansion of liquid nitrogen in loose media with different dip angles

ABSTRACT The goaf is the main disaster area for natural fires in mines, and liquid nitrogen has become an essential medium for fire prevention in goafs due to its excellent cooling and inerting properties.At present, there is no in-depth research on the transport and vaporization of liquid nitrogen after injection into the goaf, and it is impossible to quantitatively evaluate the cooling inerting effect after liquid nitrogen injection. To address the above problems, this project proposes to carry out the following research: to study the effects of different inclination angles on the transport and vaporization of liquid nitrogen and temperature distribution in the loose medium in confined space by monitoring the temperature field changes during the pressure injection of liquid nitrogen in the loose medium in confined space.The results show that the temperature field distribution is very uneven after liquid nitrogen is injected into the loose medium in the restricted space.It is found that the vaporization rate of liquid nitrogen decreases with the increase of diffusion time and diffusion area, and the instantaneous vaporization rate of liquid nitrogen decreases with the larger inclination angle under the same injection position. Compared with the horizontal state, the maximum vaporization rate decreased 84.79% when the maximum inclination angle was 15°, which indicates that the vaporization rate was greatly affected by the inclination angle of the surface. In the vertical direction of the experimental box, the cooling area of liquid nitrogen in the experimental box is mainly concentrated within 0.05 m height from the bottom of the experimental box, and the changes of the “cooling restricted zone” after liquid nitrogen injection into the goaf are further explained during the experiment.It is found that the “cooling restricted zone” mainly exists in the upper part of the goaf, under the inclined condition, and the area increases with the increase of the inclination angle, so the increase of the angle is not conducive to the effective cooling effect of liquid nitrogen.The research results of the project will help to improve the theory of liquid nitrogen fire prevention in mines and provide theoretical support for the fire prevention technology of liquid nitrogen direct injection in goafs.

Design of an open-pit gold mine by optimal pitwall profiles

ABSTRACT The overall steepness of pitwalls significantly influences the financial return of an open pit mine. In current practice, pitwall profiles are planar in cross-section. In this paper, a new geotechnical software, OptimalSlope, is employed to determine depth-varying optimal pitwall profiles for each slope sector of the mine. OptimalSlope solves a mathematical optimization problem where the overall steepness of the pitwall is maximized for the assigned stratigraphy, rock properties, and Factor of Safety (FoS). Bench geometries (bench height, bench-face inclination, and minimum berm width) are incorporated into the optimization as constraints that bind the maximum local inclination of the sought optimal profile together with any other constraint related to any geological discontinuities that may influence slope failure. The optimal profiles are always steeper than their planar counterparts—that is, the profile exhibiting the same FoS, generally up to 8 degrees, depending on rock type and constraints. To showcase the financial gains that can be achieved via OptimalSlope, the design of a gold mine in a complex geology dominated by weak rocks was initially carried out for planar pitwalls and then for optimal pitwall profiles. The pit has been divided into five geotechnical sectors, each requiring a different pitwall profile design. Adopting optimal slope profiles led to a 52.7% higher net present value and reductions in the carbon footprint and energy consumption of 0.0613 million tonnes CO2 eq and 31.3 million MJ, respectively, due to a 3.5% reduction of rock waste volume.