SIMULATION MODEL OF THE BRUSH CUTTER ROTOR WITH SIX BLADES

Brush cutters are used in forestry for the care of forest plantations in operations for cutting unwanted tree and shrub vegetation (TSV). Rotors can be used as working bodies. The rotor we are considering is a flywheel, on the outer sides of which the blades are hinged. When cutting DKR with blades, a cutting moment arises, which is transmitted through the knife to the axis of its rotation and then to the shaft driving the flywheel. When designing a brush cutter structure, the impact from the cutting forces of the DKR is decisive for the choice of drive power and rotor parameters. We designed the brush cutter rotor in CAD Solidworks to study the cutting process of the DKR. Its geometric and mass parameters were set; the kinematic links of the links were established. The input motion characteristics were set in the Motion Solidworks module and the cutting moment was applied to the knives. Virtual sensors were installed on the model to record movement characteristics. As a result of a computer experiment for three options, which differ in cutting force and the presence of a damper, the trajectories of the knives and the power consumption of the drive were established

Dynamic Evolution Mechanism of A Rock Slope with Discontinuities Under Earthquake Motions Using Shaking Table Tests

Under the impact of earthquake, even if the slopes do not fail, the integrity of rock slope structure would be damaged subjected to the seismic motion. The process of damage, destruction and failure for slopes is characterized by the dynamic evolution of stability. In the areas with active tectonic activities, frequent earthquakes have a significant effect on the attenuation of slope stability. To investigate the dynamic evolution of a rock slope under earthquake motions, a series of shaking table tests were performed. An artificial synthetic earthquake seismic wave was adopted to investigate the horizontal acceleration response. The results show that the wave field propagation results in MPGA values for the slope body above the tuff structural surface are larger than those inside the slope, and a maximum value of 3.7 is observed at slope crest. The structural surface results in a mutation of the acceleration response, which is not conducive to the slope stability. The modeled slope entered the plastic stage (input motion of 2.97 m/s2) earlier than landslides occurred (input motion of 4.46 m/s2). In addition, the safety factor of the sliding blocks was calculated based on pseudo static analysis. A good correspondence was found between the safety factors and the failure mode of the slope. The damage evolution process for the rock slope can be divided into three stages: an elastic stage (Ks=1.6–4.7), a plastic stage (Ks=0.8–1.6), and a damage stage (Ks<0.8).

Seismic Performance of Deposit Slopes with Underlying Bedrock before and after Reinforcement by Stabilizing Piles

The seismic performance of stabilizing piles used to reinforce underlying bedrock in a deposit slope is a complex soil–structure interaction problem. Two centrifuge shaking table model testswere conducted to ascertain the dynamic responses of the underlying bedrock deposit slopes without and with the use of stabilizing piles during an earthquake. Multi-stage seismic waves with various peak accelerations were applied from the bottom of each model. The differencesin the response accelerations between the deposit and bedrock increase significantly with the increase in amplitude of the input seismic waves. The presence of the rock-socketed stabilizing piles can bridge the uncoordinated movement of the bedrock and the overlying deposit to some extent. The resultant force arising from a distributed load increment on the piles caused by an earthquake is mainly concentrated in the upper part. With increases in the peak ground acceleration of the input motion, the resistance of the bedrock in front of the stabilizing piles increases and the peak resistance under the bedrock surface of the stabilizing piles gradually moves downwards.This finding indicates that the strong seismic motion significantly changes the embedded working state of the stabilizing pile.

Effect of Characteristics of Ground Motion on Seismically Induced Sliding Surface of Slopes

The seismic performance of slopes is typically evaluated with a pseudo-static method using equivalent horizontal load or with Newmark sliding block analysis. In both procedures, the definition of the potential sliding surface is a required input. The sliding surface has been reported to be marginally influenced by the input ground motion and, therefore, is most often assumed from a pseudo-static procedure. In this study, extensive series of two-dimensional dynamic nonlinear finite element analyses are performed to evaluate the sensitivity of the sliding surface on the slope geometry, soil strength parameters, and input ground motion characteristics. It is demonstrated that the sliding surface may vary with the intensity and frequency characteristics of the input motion. Slopes with inclination angle equal or less than 35° are shown to be marginally influenced by motion intensity if the mean period (Tm) < 0.3 s. However, slopes inclined at 45° are revealed to be more sensitive to the motion intensity and Tm. For motions with Tm > 0.3 s, the sliding surface is demonstrated to widen with an increase in the intensity of the input ground motions. The degree of widening increases proportionally with an increase in Tm. It is, therefore, recommended to derive sliding surfaces from a dynamic analysis for steep slopes.

Simulation-based site amplification model for shallow bedrock sites in Korea

A new simulation-based site amplification model for shallow sites with thickness less than 30 m in Korea is developed. The site amplification model consists of linear and nonlinear components that are developed from one-dimensional linear and nonlinear site response analyses. A suite of measured shear wave velocity profiles is used to develop corresponding randomized profiles. A VS30 scaled linear amplification model and a model dependent on both VS30 and site period are developed. The proposed linear models compare well with the amplification equations developed for the western United States (WUS) at short periods but show a distinct curved bump between 0.1 and 0.5 s that corresponds to the range of site natural periods of shallow sites. The response at periods longer than 0.5 s is demonstrated to be lower than those of the WUS models. The functional form widely used in both WUS and central and eastern North America (CENA), for the nonlinear component of the site amplification model, is employed in this study. The slope of the proposed nonlinear component with respect to the input motion intensity is demonstrated to be higher than those of both the WUS and CENA models, particularly for soft sites with VS30 < 300 m/s and at periods shorter than 0.2 s. The nonlinear component deviates from the models for generic sites even at low ground motion intensities. The comparisons highlight the uniqueness of the amplification characteristics of shallow sites that a generic site amplification model is unable to capture.

Effects of Stratification on Soil–Foundation–Structure Interaction: Centrifugal Observation and Numerical Simulation

It is essential to reduce structural damages caused by earthquakes in severe conditions, such as layered ground, especially when a soft soil layer is close to the surface. In this study, the kinematic and inertial interactions, two mechanisms of soil–foundation–structure interaction (SFSI), of different soil–foundation–structure systems (SFS) were investigated on uniform and layered grounds. Two layered soil profiles composed of a low stiffness layer laid over another were prepared in an equivalent shear beam container. Nine centrifuge experiments were carried out for three structures located on the surface of each ground and exposed to the Hachinohe earthquake while increasing the peak acceleration of the input motion. Numerical simulations were performed to simulate the centrifuge tests. It was found that roof motion (RM) of the tall structure increased in layered profile even though the free-field motion (FFM) decreased compared to homogeneous ground. The appearance of a soft layer beneath structures modifies the SFS system’s stiffness that causes kinematic and inertial interactions to alter to those on uniform soil profile.