Preliminary Study on Different Materials of Geogrid by using Finite Element Model

In recent years, environmental concerns related to the overexploitation of natural resources and the need to manage large amounts of wastes arising from construction activities have intensified. This paper presents a preliminary study carried out to characterize the interaction impact with different material geogrids (a polyester (PET), high-density polyethylene (HDPE), and polyurethane (PU) geogrid through Finite Element Model (FEM) simulation. The effects of the geogrid specimen size, displacement rate by the pressure through the geogrids are evaluated. The results show that the measured peak pullout resistance of the geogrid increases with the specimen size imposed displacement rate The pressure ranged from 10 000 N/m2 and 50 000 N/m2. The FEM analysis result is important due to quantify the benefit-cost ratio of geosynthetics application in pavements needed for a detailed Life-Cycle Cost Analysis (LCCA).

Deformation Characteristics of the Surrounding Rock of a Six-Lane Multiarch Tunnel under Different Excavation Conditions

Highway tunnel plays an increasingly prominent role in the development of high-grade highway traffic in mountainous countries or regions. Therefore, it is necessary to explore the deformation characteristics of the surrounding rock of a six-lane multiarch tunnel under different excavation conditions. Using the three-dimensional indoor model test and finite element analysis, this paper studies the dynamic mechanical behavior of a six-lane construction, reveals the whole process of the surrounding rock deformation process of class II surrounding rock under different excavation conditions, and puts forward the best construction and excavation method. The results show that the maximum displacement rate of excavation scheme III is the largest, and the maximum displacement rate of excavation scheme I is basically the same as that of excavation scheme II. Therefore, in terms of controlling the displacement rate of the surrounding rock, the effect of excavation scheme I is basically the same as that of excavation scheme II, while that of excavation scheme III is poor. In terms of construction technology, scheme II is simpler than scheme I and can ensure the integrity of the secondary lining. Therefore, in class II surrounding rock of the supporting project, it is recommended to adopt scheme II for construction.

Development of a Controlled Continuous Low-Dose Feeding Process

This paper proposes a feed rate control strategy for a novel volumetric micro-feeder, which can accomplish low-dose feeding of pharmaceutical raw materials with significantly different powder properties. The developed feed-forward control strategy enables a constant feed rate with a minimum deviation from the set-point, even for materials that are typically difficult to accurately feed (e.g., due to high cohesion or low density) using conventional continuous feeders. Density variations observed during the feeding process were characterized via a displacement feed factor profile for each powder. The characterized effective displacement density profile was applied in the micro-feeder system to proactively control the feed rate by manipulating the powder displacement rate (i.e., computing the feed rate from the powder displacement rate). Based on the displacement feed factor profile, the feed rate can be predicted during the feeding process and at any feed rate set-point. Three pharmaceutically relevant materials were used for the micro-feeder evaluation: di-calcium phosphate (large-particle system, high density), croscarmellose sodium (small-particle system, medium density), and barium sulfate (very small-particle <10 μm, high density). A significant improvement in the feeding performance was achieved for all investigated materials. The feed rate deviation from the set-point and its relative standard deviation were minimal compared to operations without the control strategy.

Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part I: sintering and densification

Five TiAl–Ti3AlC2 composite samples containing (10, 15, 20, 25 and 30 wt% Ti3AlC2 MAX phase) were prepared by spark plasma sintering technique at 900 °C for 7 min under 40 MPa. For this purpose, metallic titanium and aluminum powders (aiming at the in-situ formation of the TiAl matrix phase) were ball-milled with predetermined contents of Ti3AlC2 MAX phase, which already was synthesized using the same metallic powders as well as graphite flakes. Displacement-time-temperature variations during the heating and sintering steps, displacement rate versus temperature, displacement rate versus time, and densification behavior were studied. Two sharp changes were detected in the diagrams: the first one, ~16 min after the start of the heating process due to the melting of Al, and the second one, after ~35 min because of the sintering progression and the applied final pressure. The highest relative densities were measured for the samples doped with 20 and 25 wt% Ti3AlC2 additives. More Ti3AlC2 addition resulted in decreased relative density because of the agglomeration of MAX phase particles.

RATE-DEPENDENT COMPACTION AND RELAXATION RESPONSE OF UNCURED PREPREGS UNDER HIGH-PRESSURE CONDITIONS

The compaction-relaxation response at different compaction rates and fiber volume fractions plays a key role in understanding the viscoelastic response of uncured prepregs. Hence, this study characterizes the time-dependent behavior of un-cured 4- layer prepregs subjected to compaction-stress relaxation test at different displacement rates i.e., 0.1 mm/min, 1.0 mm/min, and 10 mm/min, at 0.65 fiber volume fraction and allowed to relax for two hours. In this study, the complete deformation history of the Hexply M26T multilayer prepregs is measured from a stress-free state to the cured state. The effects of rate-dependent compaction-relaxation at different rates on percentages of compaction, recovery, stress change during relaxation, and permanent deformation of prepregs are computed. It was concluded that the 0.1 / displacement rate showed the lowest peak stress level and the lowest stress relaxation and permanent deformation. A viscoelastic model was used to fit the experimental data and the results showed a good agreement. The void content was determined analytically and from the XCT-aided geometrical model. It was observed that for a given test condition, the void content increases as the displacement rate increases, due to the high applied pressure. This study highlights the importance of rate-dependent compaction-relaxation behavior and the need to determine the suitable process parameters and models to manufacture high-quality aerospace composite structures.

Improved prediction method for ground surface thawing settlement caused by the melting of tunnel horizontal frozen wall

With the rapid development of urban subway tunnel, artificial ground freezing technology is becoming more and more mature. With the natural thawing of horizontal frozen wall, thawing settlement will occur on stratum due to the thawing of frozen soil and the consolidation of thawed soil, which will inevitably bring adverse impact on the surrounding environment of subway tunnel. Therefore, the establishment of a reasonable ground surface thawing settlement prediction method will provide a favorable theoretical support for predicting the ground surface deformation in advance and taking active thawing settlement control measures. In the paper, the time functions of ground surface thawing settlement and consolidation settlement of tunnel horizontal frozen wall are established based on the stochastic medium theory during natural thawing period, and the calculation methods of thawing front radius, inner radius of thawing shrinkage region and inner radius of consolidation region are proposed. The results show that the cumulative ground surface thawing settlement is larger than that of Cai et al. after considering the consolidation of the thawed soil, which fully indicates that the ground surface settlement caused by the drainage and consolidation of the thawed soil cannot be ignored. In addition, the thawing displacement rate of frozen soil is greater than the consolidation displacement rate of thawed soil during the natural thawing and the thawed soil will be consolidated at a lower settlement rate for a long time after the natural thawing period.

The Disaster Mitigation of Slow-Landslide Movement Induced By Rainfall Based on Ps-Insar Method

Disaster management is a big issue in the past few years. Talking about the disaster, an aspect that should be focussed on is mitigation. The development and the ability of Remote sensing technology have a significant impact on disaster management and significantly contribute to disaster mitigation, such as for the disaster monitoring system. The slow-landslide movement is rarely considered in disaster mitigation, even though the acceleration can increase time by time and will be more dangerous than usual. Therefore, the observation of the remote sensing technology is needed for disaster mitigation. PS-InSAR as a space-based observation method can observe the continuous movement on a site location. Thus, this study illustrates the slow-landslide movement mechanism based on remote sensing technology using the PS-InSAR method compared with rainfall data. In this study, the Sentinel-1 images and STAMPS/MTI by Hooper (2004) successfully detect the displacement rate of the Kalibawang Village, Special Region of Yogyakarta, Indonesia, with the maximum displacement rate -23 mm/year along the Line of Sight (LoS) of the satellite. The PS-InSAR result was also compared with the rainfall data, and shows a correlation of the movement during the rainfall season. Therefore, further mitigation is needed to reduce the risk of the disaster.

Displacement Rate Effects on the Mode II Shear Delamination Behavior of Carbon Fiber/Epoxy Composites

This paper studies the influence of displacement rate on mode II delamination of unidirectional carbon/epoxy composites. End-notched flexure test is performed at displacement rates of 1, 10, 100 and 500 mm/min. Experimental results reveal that the mode II fracture toughness GIIC increases with the displacement, with a maximum increment of 45% at 100 mm/min. In addition, scanning electron micrographs depict that fiber/matrix interface debonding is the major damage mechanism at 1 mm/min. At higher speeds, significant matrix-dominated shear cusps are observed contributing to higher GIIC. Besides, it is demonstrated that the proposed rate-dependent model is able to fit the experimental data from the current study and the open literature generally well. The mode II fracture toughness measured from the experiment or deduced from the proposed model can be used in the cohesive element model to predict failure. Good agreement is found between the experimental and numerical results, with a maximum difference of 10%. The numerical analyses indicate crack jump occurs suddenly after the peak load is attained, which leads to the unstable crack propagation seen in the experiment.

Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

Incorporating Persistent Scatterer Interferometry and Radon Anomaly to Understand the Anar Fault Mechanism and Observing New Evidence of Intensified Activity

Interferometric Synthetic Aperture Radar (InSAR) monitors surface change and displacement over a large area with millimeter-level precision and meter-level resolution. Anar fault, with a length of ~200 km, is located in central Iran. Recent seismological studies on the fault indicated that it is approaching the end of its seismic cycle. Although a large earthquake is imminent, the mechanism of the fault is not well understood. Therefore, understanding and discovering the mechanism of Anar fault remains a challenge. Here, we present an approach of displacement fault analysis utilizing a combination of InSAR data obtained from the persistent scatterer interferometry (PSI) method and 178 Sentinel-1 images (ascending and descending) (2017–2020). We incorporated groundwater samples from 40 wells, radon concentration anomaly mapping, Global Positioning System (GPS), and 3D displacement measurement acquired over four years (2016–2020). We investigated and monitored the deformation of the fault plate’s behavior over the last three years (2017–2020) to explore new evidence and signature of displacement. The results show that the time series analysis in the fault range has an increasing displacement rate in all dimensions. We observed that the line-of-sight (LOS) displacement rate varied from −15 mm to 5 mm per year. Our calculations show that the E–W, N–S, and vertical displacement rates of the fault blocks are 2 mm to −2 mm, 6 mm to −6 mm, and 2 mm to −4 mm per year, respectively. An anomaly map of the radon concentration shows that the complete alignment of the high concentration ranges with the fault strike and the radon concentration increased on average from 23.85 Bq/L to 25.30 Bq/L over these three years. Therefore, we predict rising the radon concentration is due to the increase in activity which resulted in a deformation. Finally, our findings show that the Anar fault is an oblique and right-lateral strike-slip with a normal component mechanism. We validated the proposed method and our results by comparing the GPS field data and PSI measurements. The root mean square error (RMSE) of the PSI measurement is estimated to be 0.142 mm. Based on the supporting evidence and signature, we conclude that the Anar fault activity increased between 2017 and 2020.