Vision-Based Approach in Contact Modelling between the Footpad of the Lander and the Analogue Representing Surface of Phobos

Identifying solar system surface properties of celestial bodies requires the conducting of many tests and experiments in conditions similar to those found on various objects. One of the first tasks to be solved by engineers is determining the contact condition between the lander and the surface of a given celestial body during landing in a microgravity environment. This paper presents the results of experimental studies and numerical simulations of the contact phenomenon between the lander foot model and the Phobos analogue. The main goal of the experimental tests was to obtain measured deformation data of the studied analogues using 2D and 3D vision systems, which were employed to analyze the behavior of the lander foot and the surface of the studied analogue itself and to calibrate the numerical models. The analogue representing the Phobos surface was foam concrete. The variable parameters in the study were the analogue thickness and the lander foot velocity at the time of contact. Tests were conducted for three different contact velocities of 1.2 m/s, 3.0 m/s, and 3.5 m/s. Taking into account the mass of the lander foot model, kinetic energies of 30.28 J, 189.22 J, and 257.56 J were obtained. The results showed that at low contact velocities, and thus low kinetic energies, no significant differences in behavior of the material directly under the lander foot were observed, and similar values of forces in the lander foot were obtained. For higher contact velocities, the behavior of analogues with varying thicknesses was different, resulting in different values of analogue deformation and dynamics of increments and decrements of force in the lander foot itself. Although performed on a single material, the experiments revealed different behaviors depending on its thickness at the same impact energy. This is an essential guideline for engineers who need to take this fact into account when designing the lander itself.

Study on Deformation and Stability of Rock-Like Materials Retaining Structure during Collaborative Construction of Super-Adjacent Underground Project

The collaborative construction of undercrossing tunneling of Gongchang Road and the adjacent Metro Line 6 extension station section in Shenzhen is difficult and of high risk. In view of these characteristics, this paper studied the deformation and stability of rock-like material retaining structures in the process of underground engineering collaboration by combining the measured deformation data and the circular slide theory based on the limit equilibrium method. The results show that due to the difference between the supporting systems of rock-like materials on both sides and other reasons, the upper part of the retaining structure and the limited soil in the adjacent area tilt greatly to one side at the same time, and the surface settlement in the limited soil area also increases with the increase of the excavation depth of the foundation pit. On the basis of measured deformation data analysis, the mechanical model for calculating the stability concerning the relationship between the adjacent distance L of the deep foundation pit and the vertical distance D ′ between the lowest support of the foundation pit and the bottom of retaining structures was established. Then, the calculation formula for the against basal heave stability covering different adjacent degrees was established. Besides, the applicability of the calculation method was verified by combining it with the actual engineering and related prediction theories, which further proves that the research results have certain theoretical value and engineering significance, and can provide a reference for the rock-like material retaining structures design and stability analysis of similar projects.

Different Deformation Patterns in High Core Wall Rockfill Dams: A Case Study of the Maoergai and Qiaoqi Dams

The time-dependent behaviour of high rockfill dams is complex and not easy to accurately predict. Many discrepancies were revealed by the comparison of the observed deformation histories of different dams, and the deformation of some high rockfill dams did not correspond to the general deformation law. Field monitoring is therefore an effective method for understanding complex dam deformation behaviour. In this paper, actual measured deformation data resulting from continuous monitoring of the Maoergai and Qiaoqi dams are analysed. These two dams have similar heights, crest lengths, and alluvium overburden thicknesses. Our aim is to explain the actual deformation histories on the basis of the mechanical behaviours of these dams in order to warn engineers about potential problems that cannot be predicted. The results indicate that the deformation patterns of the two dams are completely different. The dam construction and water impoundment schedule is the major reason for the different horizontal displacement patterns. The reservoir filling rates and rainfall are the main reasons for the different settlement patterns. The case histories are useful for understanding the wide range of possible postconstruction deformation in a dam.

Alüviyal Ortamda Derin Kazı Problemi

The basement needs that emerged in the city centers have led to a more frequent encounter with deep excavation problems, which is one of the important issues of Geotechnical Engineering. This situation requires additional care and experience for soil and rock environments especially in deep excavations where different shear resistance parameters can be mobilized both in the short term and in the long term. In this paper, the stages of soil investigation, analysis, manufacturing and measured deformation were evaluated within the scope of the deep excavation planned and carried out in Adapazari city center. Following the excavation and filling phase at a depth of 4 m following the construction of the secant piles, the deformation readings were particularly noticeable on the eastern border. SAU Geotechnical Working Group conducted an investigation study to understand the causes of the incident and to take the necessary measures, if any. After the investigation, the reason of the deformations was estimated to be due to the sudden drainage of groundwater during the construction of the piles, and subsequent consolidation of the clayey layers beneath the existing 5-storey structure adjacent to it. The excavation has been successfully completed with the projected horizontal support system and it has been observed that the application of strut in the deep excavation support system creates practical difficulties especially in small parcels during the excavation phase.

Spring Deformation Gauge for Measuring Local Deformations in Triaxial Apparatus

Local measurement of deformations of a soil specimen has become inevitable for accurate determination of soil stiffness in triaxial tests. Although there are now many devices that can be used to perform this task, each has its own advantages and limitations that render development of new devices with better desirable features. This paper presents an innovative device called spring deformation gauge (SDG) that has many advantages over many of the existing devices and can be readily manufactured in both research and commercial laboratories. The device is based on using a highly flexible, yet very strong metal strip of spring steel secured between two stiff, stainless steel L-shaped legs; the spring strip is provided with four strain gauges. With this arrangement, local deformation of a specimen is transferred into significant bending in the metal strip and elongation or shortening of the strain gauges. In addition to being very cost effective, the SDG is characterized by the ability to control both range and resolution of measured deformation, its linear output, and a clever pinning mechanism that protects it from being damaged when it goes out of range. Success of the SDG was demonstrated in a true K0 test on carbonate sand.

Derivation of Ply Specific Stiffness Parameters of Fiber Reinforced Polymer Laminates via Inverse Solution of Classical Laminate Theory

The realistic estimation of the ply stiffness parameters of polymer composite laminates is a big challenge nowadays in industrial practice. In this paper a new, innovative concept is introduced that is based on the backward use of Classical Laminate Theory (CLT). The innovation in this new concept is (amongst others): possibility to infer the stiffness constants from the simple mechanical tests of specimens with multidirectional ply stack-up identical to the part to design. In addition the new method is manifested in a form of a compact equation that surely returns the measured deformation of the tested specimen on laminate level. The mathematical background of this concept is slightly more complex than what the conventional techniques offer, however its explicit form allows to code it in any automatic systems (e.g. user script) that can be run in Finite Element environment or as part of the software of a mechanical testing frame.