Extremely large post-liquefaction deformations of saturated sand under cyclic torsional shear loading

The effect of static shear stress on the undrained cyclic behavior of saturated Toyoura sand was studied by conducting a series of torsional shear tests up to double amplitude shear strain of about 100%. After being isotropically consolidated, the specimens were subjected to drained monotonic torsional shear loading, and then, cyclic torsional shear stress was applied under undrained condition. The amplitude of combined static and cyclic shear stress was kept constant by correcting the measured value for the effect of membrane force. Based on these test results, it was found that the effective stress path and the stress-strain curve were affected by the initial static shear stress. Accumulation of shear strain was clearly noticed in the same direction where the static shear stress was applied. Localization of specimen deformation, which increases with the shear strain level, was observed

Simplified procedures to compute earthquake-induced sliding and overturning displacements of retaining walls

特集2 耐震構造学研究グループ (ERS

Suppression of Propionibacterium acnes

Purpose. Macrophages serve as sweepers of microbes and inflammation-derived wastes and regulators of inflammation. Some traditional Japanese medicines are reported to have adjuvant effects by modifying macrophages. Our aim was to characterize the actions of jumihaidokuto (JHT) for treatment of skin inflammations including acne vulgaris, in which Propionibacterium acnes has pathogenic roles. Methods. Dermatitis was induced in rat ears by intradermal injection of P. acnes. JHT or prednisolone (PDN) was given orally, and ear thickness and histology were evaluated. The effects of constituents and metabolites of JHT on monocytes were tested by cell-based assays using the human monocytic THP-1 cell. Results. JHT and PDN suppressed the ear thickness induced by P. acnes injection. Histological examinations revealed that JHT, but not PDN, promoted macrophage accumulation at 24 h after the injection. PDN suppressed the macrophage chemokine MCP-1 in the inflamed ears, while JHT did not affect it. The JHT constituents liquiritigenin and isoliquiritin increased expression of CD86 (type-1 macrophage marker) and CD192 (MCP-1 receptor) and enhanced phagocytosis by THP-1. Conclusions. JHT suppressed dermatitis, probably by enhancing type-1 macrophage functions, with an action different from PDN. JHT may be a beneficial drug in treatment of skin inflammation induced by P. acnes

Experimental study on anisotropy of strength characteristics of cement treated sand

特集 都市基盤の安全とICUSの活

Osteoclasts adapt to physioxia perturbation through DNA demethylation

Oxygen plays an important role in diverse biological processes. However, since quantitation of the partial pressure of cellular oxygen in vivo is challenging, the extent of oxygen perturbation in situ and its cellular response remains underexplored. Using two-photon phosphorescence lifetime imaging microscopy, we determine the physiological range of oxygen tension in osteoclasts of live mice. We find that oxygen tension ranges from 17.4 to 36.4 mmHg, under hypoxic and normoxic conditions, respectively. Physiological normoxia thus corresponds to 5% and hypoxia to 2% oxygen in osteoclasts. Hypoxia in this range severely limits osteoclastogenesis, independent of energy metabolism and hypoxia-inducible factor activity. We observe that hypoxia decreases ten-eleven translocation (TET) activity. Tet2/3 cooperatively induces Prdm1 expression via oxygen-dependent DNA demethylation, which in turn activates NFATc1 required for osteoclastogenesis. Taken together, our results reveal that TET enzymes, acting as functional oxygen sensors, regulate osteoclastogenesis within the physiological range of oxygen tension, thus opening new avenues for research on in vivo response to oxygen perturbation.Nishikawa K., Seno S., Yoshihara T., et al. Osteoclasts adapt to physioxia perturbation through DNA demethylation. EMBO Reports 22, e53035 (2021); https://doi.org/10.15252/embr.202153035

A method for assessing failure behavior of sand with initial static shear

In sloped ground, soil elements are subjected to an initial static shear stress on the horizontal plane or an assumed failure surface. During earthquake shaking, these elements are subjected to additional cyclic shear stress due to shear waves propagating vertically upward from bedrock. The superimposition of static and cyclic shear stresses can have major effects on the response of the soil, leading to liquefaction-induced failure behavior of natural and artificial slopes of sandy deposits and the consequent development of extremely large ground deformation. In order to address the above issue, in this paper, a method to assess the failure behavior of sand specimens with initial static shear under undrained cyclic shear loading is presented. Its applicability has been investigated on a wide range of combinations of static and cyclic shear stresses on very loose, loose and dense sand by referring to: (i) the results of undrained cyclic torsional shear tests carried out on saturated Toyoura sand specimens; and (ii) a number of single-element numerical simulations by employing an elasto-plastic constitutive model developed at the Institute of Industrial Science (IIS), University of Tokyo

Liquefaction and failure mechanisms of sandy sloped ground during earthquakes: a comparison between laboratory and field observations

Prediction of ground failure involving earthquake-induced liquefaction of sloped sandy deposits is a major challenge in geomechanics due to the great number of factors that need to be considered such as initial static shear stress, cyclic shear stress, density state, confining pressure, loading conditions etc. This paper briefly describes the triggers (stress conditions) and the consequences (deformation behaviour) for three distinct failure modes that can be produced by an earthquake on sloped ground consisting of loose saturated sand. Such failure mechanisms were observed in the laboratory by performing undrained monotonic and cyclic torsional simple shear tests on Toyoura sand specimens. Most importantly, a practical method for assessing the failure behaviour of sandy-sloped ground undergoing undrained cyclic shearing based on sand failure characteristics observed in the laboratory is also presented. As an example, this method was used to satisfactorily predict slope failure that occurred in Ebigase area (Niigata City, Japan) during the 1964 Niigata earthquake

Effects of initial static shear on liquefaction and large deformation properties of loose saturated Toyoura sand in undrained cyclic torsional shear tests

This study focused on the role which static shear plays on the large deformation behavior of loose saturated sand during undrained cyclic loading. A series of undrained cyclic torsional shear tests was performed on saturated Toyoura sand specimens up to single amplitude shear strain exceeding 50%. Three types of cyclic loading patterns, i.e., stress reversal, intermediate and non-reversal, were employed by varying the initial static shear level and the cyclic shear stress amplitude. The observed types of failure could be distinguished into liquefaction (cyclic and rapid flow) and residual deformation by comparing both monotonic and cyclic undrained behavior. It was found that the presence of initial static shear does not always lead to an increase in the resistance to liquefaction or strain accumulation; they could either increase or decrease with an increasing initial static shear level depending on the type of loading pattern and failure behavior. In addition, according to the failure behavior which the specimens exhibited, three modes of development of large residual deformation were observed

Utekočinjenje tal v porečju reke Tone med potresom ob vzhodni obali Japonske 2011

A brief report about the liquefaction damage in the Tone river basin, caused by the 2011 earthquake off the Pacific coast of Tohoku, is presented. It includes sand boiling, damage to river dikes, the settlement and tilt of superstructures, the uplift of light underground structures and lateral spreading. A history of land reclamation along the Tone river is briefly presented to understand why extensive liquefaction took place predominantly inreclaimed land. The recorded ground motions near the river were analyzed andcompared to near-source ground motions. The effects of the site location and the ground conditions during the peak ground acceleration are discussed.Članek na kratko poroča o primerih utekočinjenja tal v porečju reke Tone zaradi potresa ob vzhodni obali Japonske leta 2011. Predstavljeni so primeri pojava kipečih peskov, poškodbe na rečnih nasipih, posedki in nagibanja objektov, dvižki lahkih podzemnih objektov in bočno razrivanje površja. Za lažje razumevanje vzrokov pojava velikega števila primerov utekočinjenja tal na melioriranih področjih, je na kratko predstavljena zgodovina poteka melioracij ob reki Tone. V članku so presojani zapisi premikov tal na območju reke. Izvedena je njihova primerjava s premiki iz območij bližje žarišču potresa. Prispevek razpravlja tudi o vplivih lokacije in sestavi tal na največje pospeške temeljnih tal