Abstract Considering the influence of tensile plastic strain of intact rock on tensile strength and elastic modulus. The influence of arch curvature and height of the straight wall on the progressive failure of surrounding rock under different confining pressures are simulated based on the Mohr-Coulomb constitutive model and the nonlinear CWFS criterion of friction strengthening and cohesion weakening. The results show that when λ 1 = 0.2, the difference between vertical load and horizontal load is large, the buckling failure of rock burst and slab cracking is obvious, and the sectional curvature effect is obvious. When λ 3 = 0.5, the buckling failure of rock burst and slab cracking is very limited, the sectional curvature effect is reduced, and the confining pressure effect of rock burst and slab cracking is obvious. The shear yield localization of the surrounding rock is sensitive to sectional curvature, and the sectional curvature effect of shear failure under different lateral pressure coefficients is obvious. The numerical calculation results are consistent with the failure law of surrounding rock obtained from field and laboratory tests, which can provide a reference for tunnel excavation and support design.
Aiming at the development and utilization of underground space in soft soil area, in order to study the influence of pipe jacking construction on the deformation disturbance of existing subway tunnels in soft soil area, the LSTM deep learning algorithm is used to train and verify the LSTM network model, and the settlement deformation of measuring points is predicted. The calculation results show that the variation law of the predicted value is very close to the measured value. The model predicts that the error range of the existing subway tunnel deformation during the pipe jacking construction process can be controlled at the millimeter level, within the allowable error range, and the implementation process is convenient and quick, without too much manual intervention. Under certain conditions, it can replace numerical calculations that are time-consuming and sensitive to grid and constitutive parameters.
Based on the construction method of reserved underpass space for shield tunneling and Hangzhou Metro Line 7 under Qianjiang Century City construction project. A three-dimensional calculation model of soil reinforcement with reserved underpass space was established by using numerical simulation method, and the mechanical disturbance of soil around the tunnel during the shield tunneling process was analyzed. The results show that under the condition of local soil reinforcement, heave deformation exists in the strengthened area, resulting in a large relative displacement between the local strengthened area and surrounding soil. That results in stress concentration at the interface between the reinforcement area and the surrounding soil. The isolation and protection effect of the diaphragm wall and reducing pile on the soil is revealed by monitoring the displacement.
The EPC project is the tendency of China′s AEC industries development. However, due to the low level of information management in the domestic AEC industries, the advantages of EPC projects are difficult to be shown. Through the integration of BIM technologies and EPC mode, the complementary advantages of the two can make EPC management in a more scientific and efficient way. This paper takes the urban tunnel engineering EPC project as the carrier to conduct the exploration and practice of BIM technologies in EPC project management. It focuses on the feasibility and scientific combination of EPC mode and BIM technologies from the perspectives of design, schedule management, safety and civilized construction.
Abstract Rock breaking technology based on dry ice and energy-gathered agent has been developed and successfully applied in trench excavation for construction of oil pipeline. The vibration velocity waveform induced by this technology was monitored in site test to determine the attenuation law of vibration velocity with hypocentral distance. The results show that this rock breaking technology is effective method of trench excavation. It does not excessively damage the adjacent rock mass, ensuring the integrity of ditch walls. The vibration velocity induced by this technology is decay with the increase of hypocentral distance. At the hypocentral distance of 10m, the vibration velocity reduces to less than 20mm/s, which meets the requirements of the safety standard of blasting vibration in general buildings engineering. The results of this experiment have an important guiding effect on the field engineering practice and application of rock breaking technology based on dry ice and energy-gathered agent.
A rigorous semi-analytical method is proposed for the consolidation analysis of soft soils reinforced with stone columns, which is subjected to haversine cyclic loadings. The closed-form solutions of effective vertical stress, excess pore pressure, and average degree of consolidation are derived using Fourier harmonic analysis, where the effects of the smear and well resistance of stone columns on the consolidation behaviour are considered. From a numerical parametric study, it is indicated that the consolidation behaviour of the clay layer reinforced with stone columns is dependent on the physical and mechanical properties of soft soils and stone columns, and the applied cyclic loadings. The numerical results also show that an increase in number of loading cycles can cause the response of reinforced soft soil to achieve a steady state, whereas the frequency, the elastic modulus ratio, the permeability ratio, and the radius ratio of stone columns to soil influence the consolidation behaviour of soft clay reinforced with stone columns.
Summary Drought is an abiotic stress that affects plant growth, and lipids are the main economic factor in the agricultural production of oil crops. However, the molecular mechanisms of drought response function in lipid metabolism remain little known. In this study, overexpression ( OE ) of different copies of the drought response genes LEA 3 and VOC enhanced both drought tolerance and oil content in Brassica napus and Arabidopsis . Meanwhile, seed size, membrane stability and seed weight were also improved in OE lines. In contrast, oil content and drought tolerance were decreased in the At LEA 3 mutant ( atlea3 ) and At VOC ‐ RNA i of Arabidopsis and in both Bn LEA ‐ RNA i and Bn VOC ‐ RNA i B. napus RNA i lines. Hybrids between two lines with increased or reduced expression ( LEA 3‐ OE with VOC ‐ OE , atlea3 with At VOC ‐ RNA i) showed corresponding stronger trends in drought tolerance and lipid metabolism. Comparative transcriptomic analysis revealed the mechanisms of drought response gene function in lipid accumulation and drought tolerance. Gene networks involved in fatty acid ( FA ) synthesis and FA degradation were up‐ and down‐regulated in OE lines, respectively. Key genes in the photosynthetic system and reactive oxygen species ( ROS ) metabolism were up‐regulated in OE lines and down‐regulated in atlea3 and At VOC ‐ RNA i lines, including LACS 9 , LIPASE 1 , PSAN , LOX 2 and SOD 1 . Further analysis of photosynthetic and ROS enzymatic activities confirmed that the drought response genes LEA 3 and VOC altered lipid accumulation mainly via enhancing photosynthetic efficiency and reducing ROS . The present study provides a novel way to improve lipid accumulation in plants, especially in oil production crops.
In traditional explosive blasting, the elevation amplification effect is an important aspect that cannot be ignored in the study of vibration disasters. Compared with this type of vibration, the elevation amplification effect of vibration induced by pneumatic rock breaking with carbon dioxide ice pow-der was explored through on-site vibration monitoring experiments. The results showed peak particle velocity increased when the sensor was higher than the vibration source, indicating that vibration induced by pneumatic rock breaking with carbon dioxide ice powder, like explosive blasting, has an elevation amplification effect. However, the elevation effect of vibration induced by pneumatic rock breaking with carbon dioxide ice powder mainly manifests as an amplification of the low-frequency vibration component, suppressing and weakening the high-frequency vibration. Others, the elevation amplification effect is only reflected within a certain distance. As the distance to the vibration source increases, peak particle velocity returns to its standard value and follows the existing attenuation rule. The elevation factor no longer affects the propagation and attenuation of vibration within the rock mass.
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