Stability Analysis of Large Section Rocky Tunnel Support Structure

In order to study the stress characteristics of the initial support and secondary lining of the large section tunnel and to solve the problem of secondary lining cracking during operation. Taking the large section tunnel in Zihong village, Qi County as the research object, a numerical simulation method was used to establish a finite element model of the large section tunnel. So as to simulate and analyze the stress characteristics of the support structure of this tunnel. Through the simulation of the initial support and second lining of this large section tunnel in terms of displacement, stress, plastic zone damage and anchor shaft force, the results show that as the excavation progresses, the stress and displacement on the surface of the newly excavated tunnel profile is faster, especially at the side walls and arch footings, the stress and displacement values are slightly larger than other characteristic points, but the final values are stable and converge, and are basically consistent with the field monitoring results, which indicates that this support system is basically in stable state. Therefore, during the tunnel excavation and support process, special attention should be paid to the stability of the sidewalls and footings, and the results of this study will be of great practical significance for tunnel construction and maintenance.

Dynamic evolution in mechanical characteristics of complex supporting structures during large section tunnel construction

The shallow tunnelling method(STM)often uses temporary supports to divide large section tunnels into several closed or semiclosed sections so as to share the upper load.The complex support system composed of primary and temporary supports can ensure safety during tunnel construction.Based on the large section tunnel of Beijing Subway Line 12,the mechanical characteristics of support system by the double-side-drift method(DSDM)during excavation and demolition were analyzed through numerical simulation and monitoring.The study showed that the middle cave excavation was the most critical stage of the DSDM,during which the load on the supporting structure increased significantly.The temporary vertical support bore most of the new load during middle cave excavation.During the demolition stage,the load was redistributed,which caused arch settlement and section convergence.The removal of the temporary vertical support exerted the greatest impact in this process.The lateral temporary inverted arch changed from axial compression to axial tension after the middle and lower caves were excavated.Based on the mechanical characteristics of the support system,some engineering suggestions were proposed for large section tunnel construction.These research results can provide reference for the design and construction of similar large section tunnels.

Development of Non-Quenched Prehardened Steel for Large Section Plastic Mould

In order to meet the demand of prehardened steel for large section plastic mould and save energy, a nonquenched prehardened （NQP） steel is developed. The temperature field of a large block is researched by finite element method simulation and 9 test steels are designed in the laboratory. Their microstructures and hardness are investigated when they are air cooled and control cooled at cooling rate similar to the simulation. The result shows that the hardness uniformity through section is closely correlated to bainitic hardenability for the NQP steel, and the hardness of one test steel （0.27C-1.95Mn-1.04Cr-0.45Mo-0.1V） fluctuates between HRC 40 and 43 under both cooling conditions. The test steel has better machinability compared with C45 steel, and the NQP steel is produced successfully in the factory based on the laboratory results. Its microstructure is bainite, and it is distributed uniformly through the size of 460 mm×800 mm×3 200 mm.

Application of the Largest Movable Mold EMS on a Large Section Size CC Bloom

The largest movable mold EMS developed by POSCO in collaboration with Daineli-Rotelec for improving internal quality of a large CC bloom is being used at a large size bloom caster of POSCO since 2011.Internal quality of carbon steel CC bloom of 700×700 mm~2 section size with the mold EMS was much improved compared with without the mold EMS.Equiaxed zone ratio increased from 50%to 100%and the grain of equiaxed structure became globular and fine.Top shrinkage was also much reduced by applying the movable mold EMS.

Crack elongation and its width of large depth reinforced concrete beams

In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.

Artificial intelligence recognition of pathological T stage and tumor invasion in rectal cancer based on large panoramic pathological sections

Background The incidence of colorectal cancer is increasing worldwide,and it currently ranks third among all cancers.Moreover,pathological diagnosis is becoming increasingly arduous.Artificial intelligence has demon-strated the ability to fully excavate image features and assist doctors in making decisions.Large panoramic patho-logical sections contain considerable amounts of pathological information.In this study,we used large panoramic pathological sections to establish a deep learning model to assist pathologists in identifying cancerous areas on whole-slide images of rectal cancer,as well as for T staging and prognostic analysis.Methods We collected 126 cases of primary rectal cancer from the Affiliated Hospital of Qingdao University West Coast Hospital District(internal dataset)and 42 cases from Shinan and Laoshan Hospital District(external dataset)that had tissue surgically removed from January to September 2019.After sectioning,staining,and scanning,a total of 2350 hematoxylin-eosin-stained whole-slide images were obtained.The patients in the internal dataset were randomly divided into a training cohort(n=88)and a test cohort(n=38)at a ratio of 7:3.We chose DeepLabV3+and ResNet50 as target models for our experiment.We used the Dice similarity coefficient,accuracy,sensitivity,specificity,receiver operating characteristic(ROC)curve,and area under the curve(AUC)to evaluate the performance of the artificial intelligence platform in the test set and validation set.Finally,we followed up patients and examined their prognosis and short-term survival to corroborate the value of T-staging investigations.Results In the test set,the accuracy of image segmentation was 95.8%,the Dice coefficient was 0.92,the accuracy of automatic T-staging recognition was 86%,and the ROC AUC value was 0.93.In the validation set,the accuracy of image segmentation was 95.3%,the Dice coefficient was 0.90,the accuracy of automatic classification was 85%,the ROC AUC value was 0.92,and the image analysis time was 0.2 s.There was a difference in survival in patients with local recurrence or distant metastasis as the outcome at follow-up.Univariate analysis showed that T stage,N stage,preoperative carcinoembryonic antigen(CEA)level,and tumor location were risk factors for postoperative recurrence or metastasis in patients with rectal cancer.When these factors were included in a multivariate analysis,only preoperative CEA level and N stage showed significant differences.Conclusion The deep convolutional neural networks we have establish can assist clinicians in making decisions of T-stage judgment and improve diagnostic efficiency.Using large panoramic pathological sections enables better judgment of the condition of tumors and accurate pathological diagnoses,which has certain clinical application value.