3 research outputs found

    Frictional resistance calculation and jacking force prediction of rectangular pipe jacking

    No full text
    Abstract In practical engineering, whilst estimating the jacking force of rectangular pipe jacking using an empirical formula, the results obtained from said formula deviate from reality and manifest inadequate engineering guidance. The equations governing the applied force during the installation of rectangular pipe jacking have been derived for various contact states involving the interaction between the pipe, slurry, and soil. The distinct stress conditions in the pipe jacking process as well as the shear-friction mechanism between the pipe and the surrounding soil have been taken into account. The displacement control method is introduced to simulate the pipe–slurry–soil contact friction during the pipe jacking process in FLAC3D. Additionally, the pipe jacking behavior, pipe–slurry–soil contact frictional force, and variation law of the jacking force are also simulated. Mutual verification was carried out using the results obtained from field monitoring, numerical and theoretical. The findings are as follows: the established equations for calculating pipe jacking force are highly applicable across various conditions of pipe–slurry–soil contact, and the outcomes derived from theoretical formulas align remarkably well with those obtained through field monitoring and numerical simulation. During the jacking process, the sidewalls exhibit initial partial sliding followed by a complete movement as the jacking force intensifies and subsequently diminishes, eventually attaining stability during the behavior adjustment phase. Moreover, the bottom pipe–soil contact is the most common situation in actual construction

    The prevalence of premature thelarche in girls and gynecomastia in boys and the associated factors in children in Southern China

    No full text
    Abstract Background To investigate the prevalence and risk factors of premature thelarche (PT) in girls and gynecomastia (GM) in boys in Southern China. Methods We conducted a cross-sectional study of preschool children across 9 cities in Zhejiang province. A total of 6273 children in the age-group of 2–7 years were recruited from January 2014 to March 2015. Relevant information was collected from mothers through face-to-face interviews. Logistic regression models were used to examine the correlates of PT and GM. Odds ratios (ORs) with 95% confidence intervals (CIs) are reported. Results The prevalence of PT among girls was 4.8% and that of GM among boys was 0.8%. One hundred girls were diagnosed with PT before the age of 2 years; 69 (69.0%) of these girls experienced spontaneous resolution of PT. Twenty-four boys were diagnosed with GM before the age of 2 years; 10 (41.7%) of these experienced spontaneous resolution of GM. Children borne of mothers with early onset of menarche and those belonging to high-income families were at a higher risk of premature breast development. Greater consumption of eggs was associated with premature breast development in early childhood. Conclusions Socioeconomic status of family, early onset of menarche in mother, and consumption of eggs were strongly associated with premature breast development in early childhood
    corecore