Consolidation in Soft Soil – Case Study on Prefabricated Vertical Drains (PVDs)

Background: Constructing on soft ground is one of the challenges of geotechnical engineering. The unpredictable behaviour and characteristics of soft soil can cause much damage resulting in high maintenance costs in the post-construction phase. Objective: The purpose of this study is to analyse the consolidation process and ground improvement method using surcharge and a prefabricated vertical drain by measuring the accuracy of the prediction settlement value with the actual site settlement results. Methods: An effective ground improvement method is the application of a surcharge and prefabricated vertical drains (PVDs). Various methods can be used to predict the settlement effectively, one such method being PLAXIS 3D simulation. A case study on ground improvement works was selected for this research, where PVDs were constructed and implemented at the site. A few undisturbed samples were collected from the site to generate the parameters based on the lab test conducted in the simulation process. This parameter was carefully studied and representing the principal input for the 3D model, which is generated and represents the actual ground improvement method for the selected case study. The analysis was performed using a borehole and soft soil model to generate the diagram. The prediction settlement value was generated from the PLAXIS 3D analysis as the baseline comparing to the actual results. The factors that influence the settlement value, such as the length and spacing of the prefabricated vertical drain, construction method, and soil characteristics, are also discussed. Results: A predicted settlement of 2553 mm was generated by the simulation, while the actual settlement outcome at the site was 2096 mm, a difference of 457 mm, and a prediction accuracy of 82.1%. Conclusion: The study found that the combination of surcharge and prefabricated vertical drain in the ground improvement worked well. Also, discussed were the factors that influenced the accuracy of the prediction and the site results.

Vacuum-induced lateral deformation around a vertical drain in dredged slurry

The horizontal strain in the vacuum preloading/dewatering of dredged slurry is significant to the apparent clogging effect and estimation of surface settlement around a drain; however, it has seldom been investigated in previous studies. In this study, a vacuum consolidation model test assisted with the particle image velocimetry (PIV) technology was conducted. The displacement vector field was obtained through PIV analysis and image processing; it was used to visually observe the deformation features around a drain. Based on the displacement field, the vertical/horizontal strains at varied radial distances were calculated to explain the “soil pile” and apparent clogging effect. From the strain distribution with radial distances, a significant lateral compression zone near the drain and an extension zone at farther areas were confirmed. Furthermore, a simple explicit model was established to evaluate the horizontal strain within a prefabricated vertical drain unit cell considering a horizontal attenuated vacuum and compression/extension zone. Finally, this method was applied to predict the horizontal displacement in the model test. The results showed that the proposed method can estimate the lateral displacement of soft clay slurry fairly well.

PLANNING TO REPAIR THE APPROACH SLABS BRIDGE MUARA TABIRAI, RANTAU – KANDANGAN

Muara Tabirai Bridge is on the border between Rantau and Kandangan District ,which is precisely is on the street of Kalumpang-Margasari, the village of Paci, Kalumpang subdistrict. Increasing economic growth has led to the economy of the population being affected by the development of the city, gradually increasing in economic sectors as a result of global economic growth. The increase in this economy is due to the growing industry in the area. This is accompanied by the increase and needs of the population in the area that resides in the region. Unfortunately, after one year of construction of Muara Tabirai Bridge, the approach slabs bridge in the direction Kandangan on the right side suffered a decrease in the soil to damage the asphalt, due to the possibility of a landslide on the side of the road, then the implementers make alternative repairs by using a bronjong which makes the load heavier than before so that the ground that supports the burden of the heap, bronjong and traffic load can not withstand and So in this final task is done repair on the ground soil and design a retaining wall that is more suitable for the condition of the landThe basic soil repair method used is by a phased heap (Preloading) combined with the Prefabricated Vertical Drain (PVD) ,which serves as a water and air release on the soil, thus experiencing a consolidated degree of 90%. And for retaining wall against the side of the heap is used sheet pile with the type of free-standing ,which is suitable for the location of the pile located in the river. After that, the calculation of budget plan (RAB) on the Land, improvement Project,From the result of calculation obtained, a gradual heap (Preloading) carried out 0.2 m/week ,and ,a high critical heap (HCR) obtained on the high end of the plan (HR) 3.14 m obtained a security figure (SF) of 1.148 so that the heap used the soil reinforcement that is Mini pile erection so that the safety number (SF) reaches more than equal to 1.5 Prefabricated Vertical Drain (PVD) is used specification of the product PT. Teknindo Superior System installed when before done the filling is on the ground ground, planning Prefabricated Vertical Drain (PVD) using a triangular mounting pattern with a distance between PVD 1.25 m, depth 28 m and the time required is 21 weeks. Planning of soil retaining structure used is cantilever sheet pile type, obtained a total length of sheet pile of 20.938 m at STA 0 + 275 on the left and right side of the bridge. The budget plan for this basic land improvement project is Rp. 30,886,527,167

Analytical Solutions for the Radial Consolidation of Unsaturated Foundation with Prefabricated Vertical Drain Based on Fourier Series Expansion Theory

This paper presents the analytical solution of the radial consolidation of a prefabricated vertical drain (PVD) foundation under the unsaturated condition. In the proposed modeling, air and water phases in the foundation are thought to dissipate horizontally toward to the drain, and the smear effect, drain resistance and external time-dependent loading are fully considered. The analytical mathematical tools, namely the general integration method, Fourier series expansion method, decoupling method and the constant variation method, are utilized to solve the partial differential equations. Moreover, the current solutions are verified with existing solutions in the literature. Finally, a case study considering the ramp loading and exponential loading is conducted to investigate the consolidation patterns under various loading parameters. The results show that smear effect and drain resistance can significantly hinder the dissipation process of excess pore pressures, and different external loading types will lead to various dissipation characteristics (i.e., peak values).

ANALISIS PENGARUH METODE PERBAIKAN TANAH VACUUM PRELOADING TERHADAP STRUKTUR ABUTMENT DI SEKITARNYA

Soft soil in Indonesia is problematic in infrastructure development because of its low bearing capacity and takes a long time to consolidate. In general, the method used to overcome soft soil is vacuum preloading combined with prefabricated vertical drain, PVD. The purpose of the initial loading is to consolidate the soft soil layer with a load equal to or greater than the soil load during and after construction. Meanwhile, vertical can support the consolidation process. However, this method can also cause lateral movement which also affects the area outside the repair. Thus, it is necessary to model the influence distance analysis from the circumference of the repair area outside the repair. Analysis and modeling using 2D finite program elements that will be compared with results in field. The results of the comparison of the settlement for 260 days shows a different chart pattern but a corresponding final settlement. The modeling shows that the largest influence distance due to the lateral movement is cell 2, which is 11,23mTanah lunak di Indonesia menjadi problematika pada pembangunan infrastruktur dikarenakan daya dukung yang rendah serta memakan waktu penurunan konsolidasi yang lama. Pada umumnya, perbaikan tanah yang digunakan untuk mengatasi tanah lunak adalah vacuum preloading yang dikombinasikan dengan prefabricated vertical drain, PVD. Tujuan pembebanan awal adalah untuk mengkonsolidasikan lapisan tanah lunak dengan beban sama atau lebih besar dari beban tanah selama dan setelah konstruksi. Sementara drainase vertikal dapat mempercepat proses konsolidasi. Namun, metode ini juga dapat penyebabkan pergerakan lateral yang juga mempengaruhi area diluar perbaikan. Sehingga, dibutuhkan pemodelan analisis jarak pengaruh dari keliling daerah perbaikan ke daerah luar perbaikan. Analisis dan pemodelan menggunakan program elemen hingga 2D yang akan dibandingkan dengan hasil lapangan. Hasil perbandingan penurunan selama 260 hari menunjukan pola grafik yang berbeda namun penurunan akhir yang sesuai. Pemodelan menunjukan jarak pengaruh terbesar akibat pergerakan lateral berada pada cell 2 yaitu 11,23m.

Analisis Penurunan Tanah dengan Plaxis 2D dan 3D Pada Proyek Reklamasi Belawan

Penurunan tanah adalah masalah yang sering ditemukan pada konstruksi diatas tanah lunak selain pergerakan tanah dan pergeseran tanah. Tanah dengan konsistensi lunak dan memiliki permeabilitas rendah akan lambat mengalirkan air pori dalam tanah sehingga diperlukan penanganan khusus untuk mempercepat prosesnya. Salah satu metode untuk mempercepat proses pengaliran air pori pada tanah dasar yaitu dengan memberikan beban Preloading dan pemancang PVD (Pre-fabricated Vertical Drain). PVD mampu mempercepat keluarnya air pori tanah sehingga proses konsolidasi bisa berlangsung lebih cepat. Data harian penurunan tanah yang terjadi di lapangan dicatat dari settlement plate yang dipasang di lapangan. Analisis ini bertujuan untuk mengetahui perbandingan antara penurunan tanah yang dihitung menggunakan program Plaxis 2D dan 3D dibandingkan dengan penurunan yang tercatat pada settlement plate. Analisis menunjukkan bahwa besar penurunan yang terjadi pada Plaxis 2D adalah 6,47 meter dan dari analisis Plaxis 3D adalah 6,356 meter. Penurunan yang terjadi menurut pengamatan settlement plate di lapangan adalah 6,32 meter. Dapat disimpulkan bahwa analisis dengan menggunakan Plaxis 3D lebih mendekati penurunan hasil observasi dibandingkan dengan menggunakan Plaxis 2D.

PENURUNAN OPRIT JEMBATAN SEMARANG LINGKAR UTARA DAN JEMBATAN KALI JAJAR DEMAK JAWA TENGAH DENGAN PRE-FABRICATED VERTICAL DRAIN

<p><em>Construction on soft soil, often creates problems. The Semarang North Ring Bridge and Kali Jajar Bridge are the Recent soft Marine Alluvium zones located in the Pantura area which have very soft soil characteristics with a depth of more than -30.0 meters this has resulted in a very large settlement due to very small grains, flood, rob, pore water pressure increases so that the shear strength of the soil will be small, the compression is large and the permeability coefficient is small so that if the construction load exceeds the critical bearing capacity, the damage to the foundation soil will occur. To get the increase in soil bearing capacity, it can be achieved by changing the properties of the soil from the shear angle (</em>f<em>), cohesion (c) and unit weight (</em>g<em>). The settlement can be reduced by increasing the cavity density from the compression of the soil particles (Wesley, 1977). Soil improvement takes a long time, aiming to increase shear resistance so that it requires a fast time in this case is to use Pre-Fabricated Vertical Drain (Bowles 1981). The results of the analysis of the pattern of decline and the effectiveness of the use of PVD (pre-fabricated vertical drain) at the Oprit Bridge in the two research locations have the same decrease in the range of the same heap height at (H = 4 meters) there is a decrease of 117.53 cm at 64 months on the bridge. Kali Jajar (STA. 3 + 200) and there was a decrease of 268.94 cm at 37 months at the Semarang North Ring Bridge</em></p>