Search

Water can deteriorate the compositional properties of rock through softening and dissolution. The water content rate of rock has a certain effect and can cause changes in rock properties caused by the water action. In this research, to study the effects of the water content rate on the strength and brittle plasticity of limestone, uniaxial compression tests with different water content rate states were conducted, and the form of limestone damage under different water content rate conditions was analyzed. The effects of the different water content rates on the modulus of elasticity, uniaxial compressive strength, brittleness index B value, and brittleness correction index BIM value (BIM: the ratio of dissipated strain energy to releasable elastic strain energy at the peak point of the specimen) of limestone were investigated. It was found that as the rate of water content in the limestone increased from 0% to 0.27%, the penetration shear surface on the limestone's damaged surface decreased. The modulus of elasticity decreased from 8.85 to 6.76 GPa, the uniaxial compressive strength decreased from 74.11 to 57.60 MPa, the brittleness index B value decreased from 1.17 to 1.04, and the brittleness correction index BIM value increased from 0.09 to 0.26. As the rate of water content on the limestone increased, the rock's modulus of elasticity and uniaxial compressive strength decreased. Additionally, the rock's brittleness decreased, and the percentage of plastic deformation in the total deformation increased. [ABSTRACT FROM AUTHOR]

When urban subway tunnels cross existing bridge pile foundations, having a pile foundation underpinning that ensures the safe operation of existing bridges while enabling the safe construction of subway tunnels is the focus of attention. This paper takes the running tunnel project from Huaguoyuan West Station to Huaguoyuan East Station of Rail Transit Line 3 in Guiyang City, Guizhou Province as the background. The reasonableness and feasibility of the passive underpinning construction scheme for the Guihuang Viaduct was studied. The construction plan includes the following steps: underpinning pile construction, foundation pit excavation, the concreting of the underpinning bearing platform, and existing pile truncation. In order to ensure the structural safety of the existing viaduct during the construction of the pile foundation underpinning, a 3D numerical model of the construction of pile foundation underpinning and the whole process of tunnel construction was established. The settlement calculation results of the foundation pit and bridge pier were compared and analyzed with the field monitoring data to verify the accuracy of the numerical model. Further detailed analysis of the settlement of the bridge deck, the deformation of the existing piles, the axial forces of the existing piles, and the forces on the underpinning bearing platform was carried out. The results show that the bridge superstructure load can be transferred to the underpinning bearing platform smoothly after the existing pile truncation construction. The removal of obstacle piles during tunnel excavation has a very limited impact on the superstructure of the bridge, proving the reasonableness and feasibility of the construction plan. [ABSTRACT FROM AUTHOR]

The interaction mechanism between a two-lane shield tunnel and an existing tunnel during oblique underpass is a matter of widespread concern in the engineering community, and knowledge in this area remains crude. In the construction of subway tunnels in mountainous cities with huge topographical fluctuations, internal forces and deformations are inevitable in existing tunnels. To verify the applicability of existing shield construction technology and empirical parameters to the Guiyang area, a systematic and refined numerical analysis was conducted on the shield passing under the existing tunnel section of the Tao-Hua interval of Guiyang Metro Line 3. In this paper, the accuracy of the numerical simulation is verified by comparing the calculated results with the data measured in the field; the settlement pattern that appeared above the existing tunnel during the construction of the shield with slurry hardening is analyzed; the internal forces, lateral deformation, and torsional deformation of the existing tunnel caused during the excavation of the new tunnel are obtained based on the numerical simulation results; finally, the effect of the old and new tunnels on the torsional deformation and settlement of the existing tunnel under different spatial intersection angles is studied. The results show that the internal forces, lateral deformation, and surface settlement of the existing tunnel due to the diagonal underpass show obvious asymmetric characteristics. Additionally, the existing tunnel experiences local irrecoverable torsional deformation, with the maximum torsional deformation occurring at the intersection of the old and new tunnels, and the spatial intersection angle of the old and new tunnels has a great influence on the maximum settlement of the tunnel vault and arch bottom, which shows a negative correlation. [ABSTRACT FROM AUTHOR]

Direct shear tests were carried out on nonthrough jointed rock masses (NTJRM) with three types of joints under five normal stresses. The strength characteristics of shear strength, initial crack strength, and residual strength and the deformation characteristics of tangential displacement and dilatancy displacement as well as the transformation of failure mode and the variation of shear parameters of rock mass with different joint morphology are studied. Under the same normal stress, with the increase of joint undulation, the shear strength of NTJRM increases, and the corresponding tangential displacement of NTJRM increases. Two typical failure modes are observed: TTTS mode and TSSS mode. TTTS model indicates that the initial failure, extension failure, and final failure of rock mass are caused by tensile action, while the failure mode of through plane is formed by shear action. The initial failure of TSSS mode rock mass is caused by tensile action, while the expansion and final failure are caused by shear action, and the failure mode of through plane is formed under shear action. When the joint undulation is small and the normal stress is small, NTJRM will fail in TTTS mode; when the joint undulation is large and the normal stress is large, NTJRM will fail in TSSS mode. The results show that the shear parameters of NTJRM are related to the joint morphology, the bond force increases with the increase of joint undulation, and the internal friction angle increases with the increase of joint undulation. The research results of direct shear test of nonthrough jointed rock mass can provide reference for related research. [ABSTRACT FROM AUTHOR]

Although studies have reported the association of two insertion/deletion (indel) polymorphisms in the 3'-untranslated region (UTR) of the RTN4 gene with the risk of tumorigenesis, the findings are inconsistent and require further explanation. Comprehensive literature searches were undertaken in Pubmed, Embase, Web of Science, China National Knowledge Infrastructure, and WangFang database. The risk of tumorigenesis was determined using odds ratios (ORs) and 95% confidence intervals (CIs) based on STATA 12.0 software. A total of four case-control studies with 1214 patients and 1850 controls focused on the RTN4 gene TATC/- polymorphism and five case-control studies with 1625 patients and 2321 controls on the RTN4 gene CAA/- polymorphism. Pooled analysis showed that the TATC/- polymorphism was not associated with the risk of tumorigenesis under all genetic models and the CAA/- polymorphism was significantly associated with the risk of tumorigenesis under the homozygote genetic model (Del/Del vs. Ins/Ins: OR=1.32, 95%CI=1.04-1.68, P=0.02). In conclusion, the current findings suggested that the CAA/- polymorphism in the 3'-UTR of the RTN4 gene was significantly associated with the risk of tumorigenesis in the Chinese population and may serve as a valuable marker for predicting tumor risk.