This Paper discusses the difference of soft ground excavation methodologies used in China Mainland and Taiwan. A construction site in Shanghai was taken as an example. Based on the subsoil properties and basement design, 7 excavation proposals were received for analysis. It indicates the retaining methods in proposals from China are mainly gravity type” contiguous pile wall augmented with ground improvement. Bracing system appears to be less important. However, in proposals from Taiwan, diaphragm wall or PIP wall are considered as a beam system” supported by internal bracings. This analysis allows predictions of wall movement and ground settlements to be made. This Paper compares the various proposals and finally make suggestions from the Author’spoint of view.
To understand the characteristic of deep excavation in soft ground, deep excavation data in “Tien-Mou” area along MRT Tam-Shui Line were collected. Soil improvement with jet grout is used in all cases. The soil profile, parameters and monitoring data of all cases are carefully evaluated. The relationship between diaphragm wall deflection and jet grout ratio is discussed. The wall deflections after grouting and after excavation are studied, respectively. The axial force of struts are summarized and presented as enveloped earth pressure diagram for design reference. Finally, undrained shear strength and modulus of sub-grade reaction of clay are evaluated by back-analysis.
In today’s urban area, where newly developed construction sites are frequently adjacent to existing buildings. It is of great importance to consider suitable building protection measures prior to construction to avoid possible damages.
In this paper, a case history is presented to illustrate the procedure of evaluating ground improvement for the protection of adjacent buildings during excavation. Monitoring results during excavation are also presented and discussed in order to confirm the effectiveness of the adopted measures.
A case study of slope open-cut and self-stand two-row sheet piles used in excavation is presented in this paper. The involving stiffness and deformation behaviors of self-stand two-row sheet piles during excavation are interpreted and summarized in this paper based on the data resulting from fied monitoring and observation. Although the measured deflections of sheet piles in-situ are more larger than estimation and braced system is adopted to finish excavation finally. We still expect to have some help in understanding and further research of this technique.
This paper narrated cause of building damaged induced by the SMW method, which is regarded as a construction method that will not cause soil disturbance and damaged to adjacent buildings. In reality, SMW method disturbs the earth like Bored-pile method when it is constructed, particularly in soft clay with N≦4 orω≧LL, and in loose sand with N≦10. In these soils , the SMW walls may contain mud and leak. To protect adjacent buildings, the SMW method most adopt the same precautious measures as the Bored-pile method.
The application of optimization procedure in back-analysis for soil parameters during deep excavation in Taipei basin is investigated in this paper, and an integrated system RUIP based on RIDO program is developed. Simplex method is adopted as the optimization calculation and the sum of squares of differences between measured wall deflection and calculated wall deflection is used as the objective function to obtain the soil parameters. The results show that the ratio of strength parameter Su/σv?is about 0.3, the ratio, Ku/Su, ranges from 50 m-1 to 100 m-1 for Taipei clayey layers obtained from case histories, and the ratio Kh/N of Taipei sandy layers varies from 50 t/m3to 200 t/m3.
House-moving Method has been used to erect houses with shallow footingsin Taiwan for a long time. The concept of the above method is applicableto erect some excavation-induced, tilted buildings, and to replace the singlefootings with combined footings or raft foundation of some excavation-inducedtilted buildings. Case studies are presented to clarity the suitabilityand economic concerns in applying the House-moving Method.