Studies on Suction-Assisted Installation Behavior of Suction Caissons in Clay Under Various Undrained Shear Strengths

Suction caissons are widely used for anchoring floating platform and offshore wind turbines.Penetration of the suction caisson into the desired position under the combination of its self-weight and applied suction resulted from pumping out the encased water is integral to practical engineering.Model tests were carried out to investigate the suctionassisted installation of suction caissons in clay under various undrained shear strengths.It was found that there exists a critical penetration depth value.When the penetration depth is smaller than the critical value,the soil plug undrained shear strength is higher than intact clay(i.e.,clay prior to installation).However,when the penetration depth is greater than the critical penetration depth,the undrained shear strength of soil plug is lower than intact clay.The critical value decreases with the increasing consolidation time and undrained shear strength of clay.During suction-assisted installation,cracks occur around suction caissons.The installation way has little effect on the crack formation.The influence range(i.e.,the maximum distance between the crack and the suction caisson edge)was found to increase with the increasing friction coefficient of interface between the suction caisson wall and soil and decreases with the increasing soil undrained shear strength.In addition,the drained condition of the clay during installation is dominated by the caisson aspect ratio,the undrained shear strength and the friction coefficient between the caisson wall and clay.Equations to estimate the penetration resistance and the required suction to install the suction caisson are summarized.

Resistance Factor of Caisson-Tip with Internal Fillet for Suction Caissons Penetrating into Clay

This paper presents failure mechanisms of the soil at the caisson-tip with fillet during suction-assisted penetration of suction caissons in undrained clay.Theoretical solutions of resistance factor N_c of the caisson-tip are obtained in terms of the caisson-tip geometry ratio of the flat section of the caisson-tip to the caisson wall thickness m/t and adhesion factorsα_i along inside of caisson wall andα_b at the base of the caisson-tip.It is indicated that the factor N_c increases with the increase of m/t,α_i and a_b.The resistance factors N_c for the rough base(α_b=1)are larger by 0.57than that for the smooth base(α_b=0).Besides,the factors N_c of caisson-tip with flat base(m=t)are larger by 1.14 than that with full internal fillet(m=0).The required suction to penetrate suction caissons with various fillets is obtained in terms of the force equilibrium in vertical direction.The finite element limit analysis and centrifuge model test results are used to verify the rationality of the presented failure mechanisms and theoretical predictions.

Safety and efficacy of surgical treatments for axillary osmidrosis: a retrospective cohort study comparing conventional open excision with cartilage-shaver closed curettage

Aim:The aim of this study was to evaluate the usefulness of suction-assisted cartilage shaver(SACS)system closed curettage by comparing it with open excision regarding safety and efficacy.Methods:A retrospective chart review was conducted for patients with axillary osmidrosis(AO)who underwent either open excision or SACS closed curettage between 2006 and 2018.We investigated the demographic data of patients and compared the postoperative complications and outcomes of the patients undergoing the two procedures.Results:A total of 91 patients underwent SACS closed curettage and 188 patients underwent open excision.The complication rate in the SACS group(10.4%)was significantly lower than that in the open excision group(20.7%).Each procedure led to unsuccessful outcomes for two patients.Conclusion:SACS closed curettage was safer than open excision for AO.Both procedures were extremely effective.Although decision-making for surgical treatment options for AO is affected by such other factors as discomfort in dressing,recovery time,scar formation,and cost,our results should be helpful for both surgeons and patients.