prefabricated vertical drain

http://pandu-equator.com/prefabricated-vertical-drain-pvd/
1. Pendahuluan Suatu struktur bangunan karena alasan teknis, ekonomi, sosial, atau strategis terpaksa harus didirikan di atas tanah lunak, maka biasanya ada dua masalah geoteknik yang harus diselesaikan yaitu daya dukung yang rendah dan penurunan serta beda penurunan yang relatif besar. Walaupun pondasi dalam dapat mengatasi kedua masalah tersebut, penyelesaian ini menjadi tidak ekonomis bila konstruksi berdiri di atas daerah yang luas, misalnya : embankment jalan, landas pacu pesawat, kompleks perumahan, pabrik, tanki-tanki di kilang minyak, dan proyek reklamasi. Salah satu metode untuk mengatasi masalah tersebut adalah dengan menggunakan teknik prakompresi. Prakompresi adalah suatu proses pemampatan tanah pondasi dengan jalan pemberian pembebanan sementara (prabeban/preloading)sebelum konstruksi yang sesungguhnya didirikan. Proses konsolidasi akan semakin cepat terjadi dengan menggunakan metode prakompresi yang dikombinasikan dengan pemasangan Prefabricated Vertical Drain (PVD). Gambar 1 Pemasangan Prefabricated Vertical Drain (PVD)

The Construction of Suvarnabhumi Airport (or Second Bangkok International Airport) has been planned since 1960s to accommodate the rapid growth of air traffic in this region. The Suvarnabhumi Airport (SA) will not simply substitute the existing Bangkok International Airport at Don Muang, but will also develop Bangkok into an international aviation hub in Southeast Asia. The first phase of SA

In the modern world of Civil Engineering, challenges arise during the various phases of construction, starting from the project development phase to the completion of the project. One of the main factors to be considered before commencing any infrastructure project is the foundation of where it is to be built. Without a strong foundation, it’s not possible to proceed further to subsequent stages and in some cases, significant improvements may be required before starting the construction process. Although there are several different available methods for soil improvement in Civil Engineering, preloading using vacuum pressure with prefabricated vertical drains (Vacuum Consolidation Method) is one of the commonly applied techniques. Nowadays, it is widely used in countries having soft soil settlement problems. This paper presents the observations made from a soil improvement project using VCM including the site conditions and methodologies adopted during the process. The field data related to parameters such as pore pressure, settlement and shear strength improvement in natural soft clay have been presented and discussed. The degree of consolidation in the field has been back-calculated from settlement data and compared with values obtained from the 1-D consolidation equation. Field investigation tests, such as borehole tests and field vane shear tests, were performed before and after the soil improvement and it was found that the soft soil properties can be enhanced using vacuum consolidation without the use of any surcharge loading as well.

In the present study, the effect of soil disturbance on prefabricated vertical drain (PVD)-enhanced soft soil consolidation was studied using finite element (FE) analysis. Both square and triangular PVD installation arrangements were considered. The actual shapes of the PVD, disturbed zone and unit cell were preserved in the FE analysis. A parametric study for a wide range of possible hydraulic conductivity profiles with a sigmoidal shape indicated that the degree of disturbance in the immediate vicinity of the PVD and the extent of the disturbed zone are the two factors that significantly affect the consolidation rate. Proper evaluation of these factors is therefore necessary for satisfactory PVD design. A comparison was made between the degree of consolidation calculated using an analytical solution assuming a bilinear hydraulic conductivity profile and FE analysis assuming a sigmoidal hydraulic conductivity profile in the disturbed zone surrounding the PVD. The curves of degree o...

This paper presents the performance of a full-scale test embankment constructed on soft Bangkok clay with prefabricated vertical drains (PVDs) at the site of the new Bangkok International Airport in Thailand. The embankment was square in plan with a maximum height of 4.2 m, 3H:1V side slopes, and base dimensions of 40 m by 40 m. The piezometric level with depth is characterized by negative drawdown starting at around 8-10 m depth caused by excessive withdrawal of groundwater. Instrumentation was provided to monitor both horizontal and vertical movements of the test embankment. The measured increases in undrained shear strengths with depth are in agreement with the values calculated from the SHANSEP technique. The secondary compression ratio, Cα, was 0.018, or within the normal values for marine clays. The coefficient of horizontal consolidation measured in the field, Ch(field), was higher for soil at 4 and 10 m depths than for the weakest soil at 6 m depth. The back-calculated Ch(fi...