In this article, a method and procedure is proposed based on the observed significant negative side skin friction occurred to pile foundations, employed the concept of creep and relaxation and through a series of study which consisted of monitoring of settlements of various soil stratum and the induced pore water pressure during pile installation, instrumented full scale pile load test, and artificial surcharge test fill. By using the data collected, an analytical model using t-z curves may be used to evaluate the variation of negative skin friction and the future behavior of the pile foundations under additional loads.
Viaducts are commonly used in the transportation engineering in non-urban area in Taiwan recently. Because of poor underground condition, pile foundations are required for most viaducts in the Yunlin-Chiayi alluvial plain. Although piling methods are diversified in Taiwan, two piling methods, Reverse-circulation and All-casing, are most frequently used in plain area. For new viaducts constructed in the vicinity of existing viaducts, the possible adverse effects of adjacent piling on the existing foundation becomes an engineering subject to examine. This paper introduces tests conducted to evaluate the influence of piling on the adjacent underground strata at Taipo Chiayi. The tests included the monitoring of underground response when two different piling methods, an all casing and a reverse circulation , were used. According to the monitoring results, there are evidences to show that piling will disturb the adjacent underground soil strata. Such disturbance may influence the existing adjacent structures. The All-casing method had a greater disturbance on sandy soils because sandy soils may flow into the drilling casing and result in ground settlement and lateral displacement.
Various published papers and pile load testing results had shown that base-grouting the pile tip can significantly improve the allowable bearing capacity of bored piles. However, base-grouting may change the ratio between skin friction and end bearing. Therefore care must be taken to correctly interpret the load test results of a base-grouted pile. This paper describes pile load testing results of several sites where instrumented bored piles had been base-grouted and tested. The effects of base-grouting on the distribution of axial force, skin friction and end bearing were evaluated based on measurements of rebar stress transducers.
To accommodate the construction of long span bridges and to resist severe near-fault seismic forces, deeper and larger foundations capable of providing extremely large bearing capacities are often adopted in modern day bridge foundation design. This paper provides case histories to illustrate the advantages and disadvantages of selecting between large size pile foundation and caisson foundation. Design and construction procedures together with pile load test results of these high capacity foundations are addressed. Problems/solutions associated with the design/construction of these high capacity bridge foundations are discussed as well
In order to alleviate the traffic congestion problem among the Taipei metropolitan areas, the Bali-Shinden line of East-West Expressway System project is designed to satisfy both the traffic volume and also the safety of driving during the rush hour traffic. This project is designed with the long and large-diameter pile, which increases the risk of occurrence of construction difficulty. The construction difficulties occurred during the casings installation of pier numbers of NO.1R and NO.2L, in which cases, casing were restrained by the surrounding soil and thus stopped the machine from further driving and withdrawing the casing. This paper summarizes the event of this construction difficulty and investigates its causes by reviewing the local geology and pile design process. The discussion at the end of paper provides possible causes of the restrained casing situation and suggests possible revisions for future pile design.
Hsuehshan Tunnel, 12.94 kilometers long, is the longest tunnel of Taipei-Yilan Expressway. Hsuehshan Tunnel is located within the Hsuehshan Range sub-province, which is composed of slightly metamorphosed sedimentary rocks. The rocks have been folded, deformed and sheared by tectonic activities. Locally large quantity of groundwater inflow and cave-ins were encountered due to very high permeability of the rocks and high groundwater table during tunnel excavation.
Hsuehshan Tunnel deeply below the groundwater table is designed as a drainage tunnel. The inflow to the hydrological influence of the neighboring areas was studied, and treatments of cave-ins owing to large quantity of inflow in geological weak zones were established during tunnel excavation. Slight leakage occurred due to the bad working condition and structural complexities of the intersections. The leakage treatments have been established after completion of tunnel lining.
The experiences of treatments of cave-ins and leakage are described in delail as references for similar engineering encounters in future.
Taiwan is located at an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin in which fissures, joints, beddings, and even faults prevail in most of mountainous areas. While existing joints and fractures provide ideal conduits for water to flow, large volumes of groundwater are stored in aquifers in which water inflows are often encountered during tunneling. Recently, several case studies of tunneling in Taiwan demonstrate that the water inflow is the major cause for the failure. As a consequence of groundwater loss, the problem of environmental arguments may also arise. In this paper, a case study of Tsengwen reservoir transbasin diversion tunnel with emphasis on the topics of hydrogeology was presented. Several major issues, including (1) the hydrogeological field testing technique, (2) the establishment of conceptual model, (3) the modeling of three-dimensional groundwater flow, (4) the calibration and verification of the conceptual model, (5) the prediction of tunnel inflow, were introduced. The application of each approach was described in details. It is believed that the predicted results may provide useful information for reducing the uncertainties of tunnel inflow and may also clarify the impact of environment issues.