Masaru Tateyama

Application of high-speed digital CCD cameras to observe static and dynamic deformation characteristics of sand

A mesh-printed membrane was often used to evaluate the deformation of soil quantitatively, in bearing capacity tests or plain strain compression tests. The deformation of soil can be evaluated quantitatively by measuring the displacement of each mesh captured by taking pictures. However, this method requires much time to obtain the displacement and cannot be applied to the dynamic field, such as shaking table tests, because of the limitation of frame rate of the conventional analog camera. In this study, a new image processing system using a high-speed digital CCD camera was established to make it possible to evaluate the deformation characteristics of models quantitatively and automatically in both static and dynamic fields. Further, this system was applied to the shaking table tests on a retaining wall model, and the magnitude of seismic earth pressure was found to be influenced strongly by the seismic behavior of the backfill soil.

Bridge Abutment Made of Cement-Mixed Gravel Backfill

Abstract This chapter describes a new type of bridge abutment consisting of the backfill of geogrid-reinforced, cement-mixed gravely soil and a thin reinforced concrete (RC) parapet structure (i.e., a parapet) supporting a bridge girder, which was completed in 2003 for a new bullet train line in Kyushu, Japan. The backfill and the parapet are firmly fixed to each other with geogrid layers embedded in the cement-mixed backfill. This structure is very unique in that the backfill supports laterally the RC parapet rather than exerting static and dynamic earth pressure on the back face of the parapet as in the conventional-type bridge abutment, which consists of a relatively massive RC structure supporting the backfill of uncemented soil. It is shown that the new type of bridge abutment is very cost-effective. A series of model shaking table tests were performed to evaluate the seismic stability of conventional-type bridge abutments as well as several new types of bridge abutments, including the one that was actually employed to construct the prototype. Results from a series of drained triaxial compression tests on cement-mixed gravely soil are reported. It is shown that cement-mixed gravely soil should be mixed at the optimum water content for compaction energy used to construct the backfill. It is shown that the compressive strength of cement-mixed gravely soil increases considerably with compacted dry density. The design, in comparison to that of the conventional-type bridge abutment, and the staged construction procedure of the prototype bridge abutment are described. Results from field full-scale lateral loading tests on the abutment performed to ensure the design conditions are reported. The prototype bridge abutment performed very well, showing highly integrated behavior with very high connection strength between the backfill and the parapet.

Chapter 29 Bridge abutment made of cement-mixed gravel back-fill

Abstract This report describes a new type bridge abutment consisting of the backfill of geogrid-reinforced, cement-mixed gravely soil and a thin RC parapet structure (i.e., a parapet) supporting a bridge girder, which was completed in 2003 for a new bullet train line in Kyushu, Japan. The backfill and the parapet are firmly fixed to each other with geogrid layers embedded in the cement-mixed backfill. This structure is very unique in that the backfill supports laterally the RC parapet, rather than exerting static and dynamic earth pressure on the back face of the parapet in comparison with the conventional-type bridge abutment consisting of a relatively massive reinforced concrete structure supporting the backfill of uncemented soil. It is shown that the new type bridge abutment is very cost-effective. A series of model shaking table tests were performed to evaluate the seismic stability of conventional-type bridge abutments as well as several new type bridge abutments including the one that was actually employed to construct the prototype one. Results from a series of drained triaxial compression tests on cement-mixed gravely soil are reported. It is shown that cement-mixed gravely soil should be mixed at the optimum water content for compaction energy used to construct the backfill. It is shown that the compressive strength of cement-mixed gravely soil increases considerably with compacted dry density. The design, in comparison to the one of the conventional-type bridge abutment, and the staged construction procedure of the prototype bridge abutment are described. Results from field full-scale lateral loading tests on the abutment performed to ensure the design conditions are reported. The prototype bridge abutment performed very well showing highly integrated behaviour with very high connection strength between the backfill and the parapet.

A new simple method to substantially increase the seismic stability of reinforced soil structures

A preloading and prestressing (PLPS) method has been proposed to substantially decrease the transient and residual vertical compression of geosynthetic-reinforced soil (GRS) structures subjected to long-term traffic load. It is shown that by using a newly developed device (called the ratchet system) in addition to the PLPS procedure, the seismic stability of PLPS GRS structures becomes very high. The ratchet system can not only maintain high prestress when the backfill tends to contract but also prevent the expansion of the backfill, both effectively restraining the shear and bending deformation of the structure subjected to seismic load.

Study on Seismic Performance of Geogrid Reinforced Soil Retaining Walls and Deformation Characteristics of Backfill Soil

Based on results from a series of shaking table model tests on geogrid reinforced soil retaining walls, effects of material properties (i.e. pullout resistances, rupture strength and tensile rigidities) on seismic performance of reinforced soil retaining walls are discussed. Although the material properties of two geogrid models used in this study were largely different, residual displacements of wall facing were almost equal to each other. It is also attempted to obtain deformation characteristics of reinforced backfill soil from its dynamic responses and displacements of wall facing by assuming that the reinforced backfill would behave as one macro element.

Seismic design, construction and performance of geosynthetic-reinforced soil retaining walls and bridge abutments for railways in Japan

Permanent geosynthetic-reinforced soil (GRS) retaining walls (RWs) with staged-constructed full-height rigid (FHR) facing for railways, including high-speed train lines, and motorways and others have been constructed for a total length of more than 135 km in Japan. A series of small and full-scale model tests and numerical analyses were performed for the last nearly three decades to develop this technology. During the 1995 Kobe and the 2011 Great East Japan Earthquakes, a number of GRS RWs of this type performed very well. A number of embankments and conventional type RWs that collapsed by these and other earthquakes, as well as heavy rains and floods, were reconstructed to GRS RWs of this type. Based on this technology, the GRS integral bridge system was developed, which comprises a continuous girder integrated to a pair of RC facing not using bearings and backfill reinforced with geogrid layers firmly connected to the facings. The first prototype was constructed in 2011 - 2012 for a new high-speed train line in Hokkaido, Japan. This technology will be used to reconstruct two conventional type bridges that fully collapsed by tsunami during the 2011 Great East Japan Earthquake and to newly construct bridges to be highly cost-effective while highly seismic-resistant.

Application of Cement-Mixed Gravel Reinforced by Geogrid for Soft Ground Improvement

The strength of gravel increased dramatically by adding a little amount of cement and equivalent to that of concrete materials. So, the cement-mixed gravel is expected to be effective to be used as bending member. In this paper, we have described the bending member tests as conducted to investigate the bending deformation characteristics and evaluate the reinforcement by geogrid. It revealed that the peak strength of the cement-mixed gravel did not decrease when the specimen reinforced by geogrid. We proposed slab for ground improvement on soft ground additionally, as the application of bending members. Usually, on soft ground, ground-improvement piles used for the support of embankment is often excessive because of the limitation of the deformation between the piles. Therefore, the ratio of the improvement piles could be reduced by using the slab between soil structure and piles. The efficiency was evaluated by conducting shaking table tests of liquefiable soft ground. In the case of using this slab, the deformation of soft ground and embankment was less, so the efficiency of this method was satisfactorily proven.

Estimation of Ground Resistance Characteristics of Piles used in Different Construction Methods Based on a Load Test Database

The design bearing capacity of piles can be calculated by multiplying the characteristic value with its corresponding resistance factor. In this study, we proposed a method for calculating these parameters from a loading test database of several different construction methods. Initially, we proposed the formula for calculating the characteristic value by using results from a ground investigation. Secondly, we proposed the resistance factor obtained from the statistical analysis of the loading test database by use of the first-order reliability method. The proposed method can be used to compare the effectiveness of various pile construction methods with the same reliability.

STUDY ON DESIGNING METHOD OF GRS INTEGRAL BRIDGE

現在，模型実験等により高性能化が確認されたＧＲＳ一体橋梁の実用化に向け，試験橋梁を構築し，動態観測を行っている．実用展開するにあたっては，設計手法の確立が必要不可欠となるが，現時点では確立されていない．しかし，本構造の挙動のメカニズムから，補強土工法およびラーメン高架橋の設計手法が適用できると考えられる．そこで，本検討では，これらの設計手法を基に，本橋梁に対する試設計を行い，設計に関する特徴を整理することとした．

EXPERIMENTAL STUDY OF THE SPARYING PROCESSABILITY OF CONTINUOUS FIBER REINFORCED SOIL

長繊維混入補強土を用いた吹付け施工による壁面工において，壁面を構築する際には混合土と長繊維が均一に混合されなければならない．そこで本研究においては、施工性の観点を中心に、補強繊維に関する実験的研究を行った．長繊維は吹付けノズル先にて混合土と混合するため、長繊維の太さ、曲げこわさも、それぞれあまり大きい場合には均一な混合状態が得られず、これらも好適な範囲が存在することが明らかになった．繊維種類に関しては、セメント混合土を用いることから、セメントとの親和性に優れ、弾性率、強度の高いビニロンを中心に検討した結果、施工条件については検討の余地を残すものの、従来の吹付け機を用いて、従来と同等の吹付け施工に適用することが可能であることが明らかになった．