Case study of sand bag well applied on soft soil reinforcement in road widening project
Based on the case study of soft soil reinforcement on Baian interchange, Gaofu Road, Shunde District, Foshan, the designing method and monitoring program of sand bag well applied on the soft soil reinforcement in road widening project were introduced systematically. The settlement monitoring results during the preloading process indicated that the raise of the preloading height significantly increased the consolidation and settlement of soft soil ground. The settlemental rate was much greater at the beginning and medium-term of the preloading. While during the later proloading and the followed consolidating period, the settlement rate slowed down obviously. Therefore, it is very important to control the magnitude of each loading grade and the settlement rate at the beginning and medium-term of preloading. It was found that there was a desirable reinforcement effect and economic benefit applying sand bag well method to consolidate the soft soil ground at the case of overpass extension engineering in road widening project. The sand bag well method is valued being applied in similar projects.
On Distress Characteristics and Mechanism in Road Widening Engineering
When the width of a road is insufficient to meet current National Highway Standards or the need of increased traffic loading, it will be widened. But some facility distresses often appear in road widening engineering, especially the pavement distresses near the position of existing-widening subgrades integration. Several existing widened roads in Chongqing and Shanghai were chosen to investigate the facility distresses in road widening engineering. Based on the investigation and a classification of the combining modes between the existing subgrade and the widening one,the distress characteristics and mechanism in road widening engineering are proposed in this paper. It is shown that the distress resulted essentially from the instable integration and the incoordinate deformation between the existing subgrade and the widening one.
Use of Geogrid-Reinforced and Pile-Supported Earth Structures
When designing structures that will impose a significant load over a large area, such as buildings, tanks, walls, slopes or embankments, the geotechnical engineers must address the following situations, especially when dealing with weak foundation soils: bearing capacity failures, intolerable total and differential settlements, large lateral pressures and movement, and slope instability. Geogrid-reinforced and pile-supported platforms have been successfully used for supporting earth structures. In this system, geogrids create a stiffened platform that spans weak soils and prevents deflection between piles (or columns by ground improvement techniques) or pile caps from being reflected to the surface. This paper briefly discusses the mechanisms of this system and then focuses on three case studies in which geogrid-reinforced and pile-supported platforms were used for supporting segmental walls in Brazil, embankments, and a building in the US. The first two sites have peat deposits and the foundation soils are very soft. The third site had a large cut and fill situation and the anticipated differential settlement is substantial if no ground improvement is implemented. The three projects adopted three different deep foundation techniques: vibro-concrete columns (VCC), jet-grouting columns, and cast-in-place concrete piles. In this paper, each case study provides a description of the site, the design solution, construction, and performance. The performance of each project was investigated by survey, instrumentation, and/or observation. Satisfactory performances of these projects have proved the effectiveness of this technique in reducing total and differential settlements.