000018406 001__ 18406
000018406 005__ 20170118182220.0
000018406 04107 $$aeng
000018406 046__ $$k2017-01-09
000018406 100__ $$aHara, Tadashi
000018406 24500 $$aDamage Analysis of a Compound Retaining Wall Collapsed During the 2014 Earthquake in Northern Nagano

000018406 24630 $$n16.$$pProceedings of the 16th World Conference on Earthquake Engineering
000018406 260__ $$b
000018406 506__ $$arestricted
000018406 520__ $$2eng$$aA lot of structures were damaged at Horinouchi area of Hakuba village, Nagano prefecture due to the 2014 earthquake in Northern Nagano (Mw=6.3), occurred on November 22th, 2014. In this area, we found that a compound retaining wall, which has a vertical wall on a block stacking wall, has collapsed. The total height of the wall is about 5m, which has a block stacking wall about 3.5m high and a vertical wall about 1.5m high. In this research, we focused on the compound wall, analyzed the cause of damage based on field investigations. First we conducted field investigations on the compound wall. Three investigations were conducted. The first one was just after the earthquake, on November 28th, 2014. We observed the damage situation around the wall. The second one was after a month, on December 21st, 2014. We performed microtremor measurements, and sampled soils at 5 points with thin walled tube to perform static compression tests. The third one was after five months, on April 21st, 2015. We performed some simple measuring to confirm a shape and a size of the wall, and two in-situ investigations, portable dynamic cone penetration (PDCP) tests and surface wave survey. We also sampled soils at more 5 points with thin walled tube to perform cyclic triaxial tests, and soils at 36 points using core cutter to examine water content and density of the soil. In the field investigations and laboratory tests, we found out two typical features of the site. First, the back ground of the wall has alternation strata that consist of cohesive soil, whose fine contents are about 80%, and sandy soil, whose fine contents are about 30%. We can also find some traces of piping at the back ground of the wall. Second, the back ground and the foundation ground have a poor subsurface layer and steep dip in a basement layer. The poor layer whose shear velocity is 100m/s or less, from the surface to about 2m in depth. Focusing on the layer whose shear velocity is over 200m/s, in the back ground it is found from the surface to about 9m in depth, while in the foundation ground it is found from the surface to more about 12m in depth. These results reveal that the dip of the basement layer around the wall is steep, and thick poor soil deposit on the basement layer. From the result of microtremor measurements, we can find that the ratio of the horizontal component at the top of the wall and the one at the bottom of the wall is about six times in a frequency band of around 1Hz. From the above results, it is supposed that the ground motion greatly amplified at the back ground of the wall, and it seems the main factor of the damage.

000018406 540__ $$aText je chráněný podle autorského zákona č. 121/2000 Sb.
000018406 653__ $$aretaining wall, in-situ test, laboratory test

000018406 7112_ $$a16th World Conference on Earthquake Engineering$$cSantiago (CL)$$d2017-01-09 / 2017-01-13$$gWCEE16
000018406 720__ $$aHara, Tadashi$$iHazarika, Hemanta$$iTakezawa, Koichiro$$iShinagawa, Daichi$$iKuribayashi, Kentaro
000018406 8560_ $$ffischerc@itam.cas.cz
000018406 8564_ $$s1326780$$uhttps://invenio.itam.cas.cz/record/18406/files/1397.pdf$$yOriginal version of the author's contribution as presented on USB, paper 1397.
000018406 962__ $$r16048
000018406 980__ $$aPAPER