Theoretical Method of Chamber Pressure for EPB Shield Tunneling Under-Crossing Existing Metro Tunnels

Hongpeng Lai,Tengteng Wang,Zuo Kang,Rui Chen,Qiuyang Hong 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

As an increasing number of metro lines have been planned or executed in urban area, new tunnel undercrossing existing tunnels has been commonly practiced. Construction of the existing tunnel causes disturbance to the surrounding soil and hence affects the operational parameters of undercrossing tunneling especially the chamber pressure of EPB machine. However, very limited research studies this effect. To fill the gap of knowledge, this paper proposed a new method for calculating the chamber pressure of EPB tunneling machine in undercrossing project. First, the effect of existing tunnel on surrounding soil is classified as removal-and-replacement effect, excavation-induced-disturbance effect, and elastic foundation beam effect. Second, based on analysis of the mutual interaction between existing tunnel and the undercrossing tunneling, three zones have been identified to study the chamber pressure of EPB machine. Next, a new method is proposed to calculate the chamber pressure in the process of undercrossing existing tunnel. Finally, the proposed method has been verified with measured data from two engineering cases. The comparison results show that the proposed method is in good agreement with the measured data, indicating that it is reasonable with high accuracy.

A New Method based on Centrifuge Model Test for Evaluating Ground Settlement Induced by Tunneling

Hongpeng Lai,Jian Zhang,Lianyang Zhang,Rui Chen,Wanjing Yang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.6

Current methods for evaluating the ground settlement due to tunneling in loess do not fully consider the special engineering properties of loess. This paper first studied the ground settlement due to tunnel construction in loess by conducting a uniquely designed centrifuge model test. Then the ground settlements were calculated using a currently widely used method and compared with the measured values from the centrifuge model test. The results indicated a substantial difference between the calculated and measured settlement profiles. For the stratum at shallow depth, the calculated settlement profiles were flatter with smaller maximum settlement Smax at the tunnel centerline and larger settlement far from the centerline than those from the centrifuge model test; while for the stratum near the tunnel crown, the opposite was obtained. The main reason for the difference is because of the large void structure and high compressibility of loess which causes additional settlement at shallow depth. Based on the centrifuge model test results, a new method which properly considers the special engineering characteristics of loess was proposed to evaluate the settlement due to tunnel construction in loess. The calculated settlement profiles using the new method were in good agreement with those from the centrifuge model test. Finally, the new method was used to evaluate the ground settlement caused by the construction of a Metro tunnel in loess and satisfactory results were obtained.

Tip60 and p300 function antagonistically in the epigenetic regulation of HPV18 E6/E7 genes in cervical cancer HeLa cells

Yongwei Lai,Zhao He,Aowei Zhang,Zhinan Yan,Xiao Zhang,Shiyue Hu,Nan Wang,Hongpeng He 한국유전학회 2020 Genes & Genomics Vol.42 No.6

Background High-risk HPV is a causative factor of cervical cancer. HPV DNA fragments integrate into host genome resulting in the constitutive expression of HPV genes E6 and E7 under the regulation of transcription factors, such as p300 and Tip60. Interestingly, Tip60, a factor with HAT (histone acetyl transferase) activity, represses HPV18 E6/E7 genes while another HAT p300 activates the transcription of HPV18 E6/E7. Objective To explore the mechanism for the opposite roles of Tip60 and p300 in the virus gene regulation, and the influence of Tip60 and p300 in histone modifications in the regulatory sequence of HPV18 genes. Methods Tip60 or p300 was either knocked down or overexpressed in HeLa cells. The effects on HPV E6E7 expression were determined with RT-qPCR. The association of RNA polymerase II and the enrichment of acetylated or methylated histones in HPV promoter region were measured by ChIP assays with specific antibodies. Results ChIP results showed that Tip60 and p300 differently affected the modifications of histone H3K9 and the deposition of nucleosomes in HPV18 long control region (LCR). HPV18 LCR in HeLa cells is bivalent chromatin carrying both the active histone H3K9 acetylation mark and the repressive histone H3K9 trimethylation mark, the balance is maintained by Tip60 and p300. Conclusion(s) Based on the roles of Tip60 and p300 in HPV gene regulation, chemical compounds targeting Tip60 or p300 are potential anti-cervical cancer drugs.

A Study on the Formation Mechanism and Calculation Method of Surrounding Rock Pressure in Shallow-buried Loess Tunnel Considering the Influence of Vertical Joints

Mingkun Zhao,Hongpeng Lai,Yuyang Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.4

Vertical joints have significant effects on the stability of shallow-buried loess tunnel. Due to the presence of vertical joints distributed widely in loess, the formation mechanisms of surrounding rock pressure on shallow-buried loess tunnel and its computational method are far different from those in other types of soil tunnel. In this study, the distribution characteristics of surrounding rock pressure in shallow-buried loess tunnel were investigated, and discrete element software 3DEC was used to analyze the formation mechanism and development process of surrounding rock pressure in loess tunnel under the influence of joints. We correlated the stratum deformation characteristic with the frictional force caused by the mutual dislocation between joints, and revised the semi-empirical method (Chinese Code methods) in China. The results show that the measured data of radial surrounding rock pressure of shallow-buried loess tunnel are generally between 0 − 600 kPa, and 80% in the range of 0 − 200 kPa. The surrounding rock pressure increases with the burial depth, while the distribution of lateral pressure coefficient is relatively discrete. The existence of loess vertical joints (LVJs) aggravates the uneven distribution of the vertical pressure above the tunnel, and the reduction of the lateral earth pressure coefficient at rest under the influence of joints leads to an increase in pressure near the arch shoulder, these two constitute the essence of the joints action on the surrounding rock pressure. The surrounding rock pressure of the shallow-buried loess tunnel reaches the peak stress at about 0.5D from the tunnel face (D is the tunnel span), which is about 1.04 − 1.32 times of the initial stress. After the excavation of the upper step, the stress of the tunnel crown monitoring point decreased to about 60% of the initial stress. Compared with ignoring the influence of joints, the time of reaching the peak stress at the arch shoulder monitoring point is earlier, and the final stress release degree is smaller. The comparison of the analytical results (proposed method) with the numerical results and the field data exhibits good agreement, proving the proposed method's correctness.

A Novel Model for Mechanics and Safety Calculation of Pipe Roof Based on the Load Transfer Mechanism

Yang Zhou,Hongpeng Lai,Yuanpei Chen,Zhilei Li 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

A novel model is created in this paper to realize the systematic evaluation of the mechanical properties and construction safety of the pipe roof support system. The pipe roof is split into supported area, unloading area, and stable area based on the load distribution characteristics. Combining a statically indeterminate beam (for the area of unloading) with an elastic foundation beam (supported area and stability area) takes into account the mechanical effect of the pipe roof. The new model can better reflect the load transfer mechanism and the stability of the tunnel face under the pre-support. It is demonstrated that the novel model, when compared to the existing theoretical solution, is more closely related to the measured and simulated results than typical engineering cases and is practical for field application. It can provide a new idea for the design of pipe roof support and the safety evaluation of field construction.