Large Deformation Characteristics of Surrounding Rock and Support Technology of Shallow-Buried Soft Rock Roadway: A Case Study

The coal resources in the coal-rich area of western China are mostly located in the late diagenetic Cretaceous and Jurassic strata. In this paper, a study on the support of soft rock roadways was carried out in the background of the soft rock track roadway in the Jiebangou coal mine. The field investigation showed that the surrounding rocks of the roadway were weak, soft, and broken, and the surrounding rocks were cemented, with the roadway local deformation exceeding 1 m. The borehole television results showed that the surrounding rocks were mainly weak sandy mudstone and yellow mudstone. The average uniaxial compressive strength of the surrounding rock was 15.49 MPa. The roadway is a shallow buried soft rock roadway; site investigation revealed that the original U-shaped steel shed had an extremely low resistance to slip, the filling body behind the U-shaped steel shed fell off, the interaction between the U-shaped steel shed and the surrounding rock was poor, the U-shaped steel shed could not provide sufficient timely support resistance, and the bearing capacity of the U-shaped steel shed was far from consideration. The floor was not effectively supported. The floor had different degrees of the bottom drum, and frequent undercover caused new stress disturbances, which loosened the bottom corners of both rock types and made the shed legs move continuously inward, reducing the bearing capacity and actual support resistance of the bracket. Numerical calculations were performed to study the deformation characteristics of the surrounding rock of the tunnel and the yielding damage characteristics of the brace. The results showed that the current U-shack support strength was insufficient, the two sides were deformed by 950 mm, the bottom of the roadway bulged by 540 mm, and the surrounding rock was mainly shear damaged. The fall of the filler behind the shed caused damage to the U-shaped steel shed spire. Through site investigation results and numerical calculations, the deformation and damage characteristics of the soft rock roadway and its damage causes were analyzed, and the support technology system of ‘strengthening support for weak structural parts’ was proposed. This improved the mechanical properties of the weak structural support body, the stress state of the local surrounding rock, and the bearing capacity of the support structure, and effectively controlled the deformation, damage, and instability of the surrounding rock of the roadway, and deformation, damage, and destabilization of the roadway, thereby achieving overall stability for the surrounding rock of the roadway.

Improvement of Strength and Strain Characteristics of Lightweight Fiber Concrete by Electromagnetic Activation in a Vortex Layer Apparatus

The relevant problem of choosing effective materials for enclosing structures is compliance with the requirements of increased thermal resistance, reduced mass of buildings and structures, and reduced material consumption, labor intensity, and construction costs. These requirements are satisfied by structures made of lightweight fiber-reinforced concrete, which are the subject of attention of many scientists and engineers. One of the most rational requirements for industrial use is the activation of untreated components of the concrete mixture. This article is devoted to studying the influence of the activation of fiber-reinforced concrete elements in the vortex layer apparatus on concrete strength and structural characteristics. The effect of the raw component processing time of the concrete mixture on the strength and deformation characteristics of the lightweight fiber-reinforced concrete was studied. The optimal processing time for the cement–sand mortar in the VLA-75-85s was determined. It was shown that the activation of the vortex layer in the apparatus leads to an increase in strength from 27% to 61% and an improvement in the deformation characteristics of lightweight fiber-reinforced concrete by up to 12%. Furthermore, it was found that the use of activation in VLA leads to an increase in the coefficient of constructive quality for all experimentally determined strength characteristics of lightweight fiber-reinforced concrete by up to 27%.

Design and Fabrication of Pneumatically Actuated Valveless Pumps

In this study, a valveless pump was successfully designed and fabricated for the purpose of medium transportation. Different from traditional pumps, the newly designed pump utilizes an actuated or a deflected membrane, and it serves as the function of a check valve at the same time. For achieving the valveless property, an inlet or outlet port positioned in an upper- or lower-layer thin membrane was designed to be connected to an entrance or exit channel. Theoretical analysis and numerical simulation were conducted simultaneously to investigate the large deformation characteristics of the membranes and to determine the proper location of the inlet or outlet port on the proposed pump. Then, the valveless pump was fabricated on the basis of the proposed design. In the experiment, the maximum flow rate of the proposed pump exceeded 12.47 mL/min at a driving frequency of 5.0 Hz and driving pressure of 68.95 kPa.

Improving Machining Accuracy for a Robotic Arm with Hybrid Kinematic Chains Based on Deformation Characteristics

The joint deformation has great influence on machining accuracy for a robotic arm. In this paper, the deformation characteristics of the robotic arm with hybrid kinematic chains is investigated in order to improve its machining accuracy. Firstly, the deformation model of the joints has been established based on the Strain energy method and Castigliano theorem according to the robot structure. Secondly, the deformation influence coefficient (DIC) is defined to investigate the deformation influence of main components on the end-effector, and the deformation characteristics are evaluated by the simulation. Finally, a small size robotic arm prototype is established and robotic drilling comparative experiments are conducted. The theoretical and experiment results show that the machining method can be selected according to the DIC, which the force can be applied to the components with better stiffness. On the other hand, the deformation of driving components can also be reduced when the DIC cannot be adjusted to meet the accuracy requirement.

Creep Modelling of Rootstock during Holding in Watermelon Grafting

The fragile structure of a rootstock predisposes the stem to mechanical damage during grafting. Thus, it is necessary to take into account the rootstock’s rheological properties under mechanical compression when designing a clamping mechanism. This study focused on cucurbit, a typical rootstock for watermelon grafting. Firstly, we adopted a four-element Burgers model to analyze viscoelastic behavior and deformation characteristics of the rootstock, then conducted creep tests to obtain the parameters of the viscoelastic model. Next, we developed a model for the rootstock during holding based on viscoelastic parameters, loading force and contact time. Moreover, we evaluated the effect of various loading forces and test velocities on creep deformation to reveal the least damage on the rootstock. Results showed that the influence of loading force on the creep deformation was greater than test velocity. Finally, the holding test indicated that the clamping mechanism with silicone rubber can effectively prevent the damage to the stem. Specifically, the loading force should be controlled below 4 N to reduce the associated damage. Taken together, our findings provide a theoretical basis for analyzing the holding damage mechanism during watermelon grafting.