Usaha Peningkatan Daya Dukung Tanah Lempung Menggunakan Layer Krikil, Anyaman Bambu dan Kombinasi Kolom-Layer Pasir

ABSTRACT Clay soil is soil that has a low value of pressure strength and bearing capacity. The purpose of this study is using a layer of gravel, woven bamboo, and a combination of column-layer sand as an alternative to improve the carrying capacity of clay soil, then the results from the tests are compared with each other. The method in this study is experimental. The samples of soil were taken from Kalangan, Kasihan, Bantul, D.I. Yogyakarta. The foundation soil model using steel tub size 100x100x40 cm, with soil volume 100x100x30 cm. Soil loading uses steel plates that are loaded with hydraulic jacks, equipped with a proving ring as a load reader. The column-layer combination consists of 3 sand layers, 1 cm thick horizontal position and 5 cm spacing between layers. The sand column is 1 cm in diameter with a hole depth of 20 cm. The gravel layer pattern consists of 3 layers of gravel with a layer thickness of 2 cm, the distance between the layers is 5 cm. Woven bamboo pattern: 1 layer with a length of 20x20 cm. Placement of woven bamboo at a depth of 2 cm from the ground. The results of the research are; (1) The Soil is a high plasticity (CH) inorganic clay based on the USCS system, including the medium to poor clay soil group (A-7-6 (40)) based on the AASHTO system. (2) The Strengthening of gravel layer increases the ultimate bearing capacity by 2.5 times or 159.02%, while bamboo matting provides an increase in bearing capacity by 2.7 times or 170.49%, and the combination of column-layer sand by 2.2 times. or 127, 87%. (3) The reinforcement of bamboo mats provides the highest increase in bearing capacity in clay soil between the gravel layer and the combined reinforcement of the sand column and the sand layer. This shows that the use of woven bamboo is more effective as a material for strengthening clay. ABSTRAKTanah lempung adalah tanah yang mempunyai nilai kekuatan tekanan serta nilai daya dukung rendah. Tujuan penelitian ini adalah penggunaan layer kerikil, anyaman bambu, dan kombinasi kolom-layer pasir sebagai alternatif perbaikan peningkatan daya dukung tanah lempung, kemudian hasil dari pengujian dibandingkan satu sama lain. Metode yang digunakan adalah experimen. Sampel tanah diambil dari Kalangan, Kasihan, Bantul, D.I. Yogyakarta. Pemodelan tanah pondasi menggunakan bak baja ukuran 100x100x40cm, volume tanah 100x100x30cm. Pembebanan tanah menggunakan pelat baja yang dibebani dengan dongkrak hidrolik, dilengkapi proving ring sebagai pembaca beban. Kombinasi kolom-layer pasir terdiri dari 3 lapis pasir, posisi horizontal tebal 1 cm dan jarak antar lapisan 5 cm. Kolom pasir diamter 1 cm dengan kedalaman lubang 20 cm. Pola layer kerikil terdiri 3 lapis kerikil dengan ketebalan lapisan 2 cm, jarak antar lapisan 5 cm. Pola anyaman bambu:1 lapis dengan panjang-lebar anyaman 20x20 cm. Penempatan anyaman bambu pada kedalaman 2 cm dari permukaan tanah. Hasil penelitian yaitu ; (1) Tanah merupakan tanah lempung anorganik plastisitas tinggi (CH) berdasarkan sistem USCS, termasuk kelompok tanah berlempung kualitas sedang sampai buruk (A-7-6(40)) berdasarkan sistem AASHTO. (2) Perkuatan layer kerikil meningkatkan daya dukung ultimit sebesar 2,5 kali atau 159,02 %, sedangkan anyaman bambu memberikan peningkatan daya dukung sebesar 2,7 kali atau 170,49 %, dan kombinasi kolom-layer pasir sebesar 2,2 kali atau 127, 87%. (3) Perkuatan anyaman bambu memberikan peningkatan daya dukung paling tinggi pada tanah lempung diantara bahan perkuatan layer kerikil dan perkuatan gabungan kolom pasir dan layer pasir. Hal ini menunjukkan bahwa penggunaan anyaman bambu lebih efektif sebagai bahan perkuatan tanah lempung.

Soil Sample Assay Uncertainty and the Geographic Distribution of Contaminants: Error Impacts on Syracuse Trace Metal Soil Loading Analysis Results

A research team collected 3609 useful soil samples across the city of Syracuse, NY; this data collection fieldwork occurred during the two consecutive summers (mid-May to mid-August) of 2003 and 2004. Each soil sample had fifteen heavy metals (As, Cr, Cu, Co, Fe, Hg, Mo, Mn, Ni, Pb, Rb, Se, Sr, Zn, and Zr), measured during its assaying; errors for these measurements are analyzed in this paper, with an objective of contributing to the geography of error literature. Geochemistry measurements are in milligrams of heavy metal per kilogram of soil, or ppm, together with accompanying analytical measurement errors. The purpose of this paper is to summarize and portray the geographic distribution of these selected heavy metals measurement errors across the city of Syracuse. Doing so both illustrates the value of the SAAR software’s uncertainty mapping module and uncovers heavy metal characteristics in the geographic distribution of Syracuse’s soil. In addition to uncertainty visualization portraying and indicating reliability information about heavy metal levels and their geographic patterns, SAAR also provides optimized map classifications of heavy metal levels based upon their uncertainty (utilizing the Sun-Wong separability criterion) as well as an optimality criterion that simultaneously accounts for heavy metal levels and their affiliated uncertainty. One major outcome is a summary and portrayal of the geographic distribution of As, Cr, Cu, Co, Fe, Hg, Mo, Mn, Ni, Pb, Rb, Se, Sr, Zn, and Zr measurement error across the city of Syracuse.

Investigation of Corrosion Rate and Rust Expansion Form of Segment Reinforcement for Shield Tunnel by Combined Action of Soil Loading, Chloride Ion and Stray Current

Segment reinforcement corrosion can cause bearing-capacity degradation of shield tunnel, which is unsafe for the metro operation. Therefore, a three-dimensional computational model was proposed in this paper to study the corrosion rate and rust expansion form of segment reinforcement by the combined action of soil loading, chloride ion and stray current. The results show that the arch waist segment steel corrosion rate in the middle is larger than the ends. The rust expansion form of segment reinforcement appears be an eccentric circle. The radius size and circular center are related to the non-uniform corrosion coefficient and the maximum corrosion current density.

Effect of Soil Loading and Unloading on Its Acoustic Behavior

The aim of the study was to understand the changes of ultrasound-wave speed (US) and acoustic emission (AE) as a result of soil loading and unloading. The soil was dune Sand, Poorly graded, i.e., “SP” according to the Unified Soil Classification System (USCS). Natural dune sand, as well as ‎its three extracted fractions as follows: 2.36–0.6, 0.6–0.3, and 0.3–0.075 mm, were studied. The dried sand ‎samples were studied using an oedometer instrument with simultaneous measurement of load and ‎stain level. The stress range was 0 to 143.5 kPa. Each sample was loaded and unloaded while measuring US p-wave speed and AE ‎activity (number of hits) at each loading and unloading stage. The results portray the difference in the behavior of the two studied phenomena. In the ‎stress increase branch, there is a gradual increase in p-wave speed and sharp excitation of AE activity, while in ‎the stress relaxation branch there is an abrupt decrease in p-wave speed and a minor excitation of AE signals.

Dynamics of soil ingestion by growing bulls during grazing on a high sward height in the French West Indies

Free-range livestock are exposed to environmental contaminants by ingesting contaminated matrices mainly soil. Several works evaluated precisely the soil ingestion and its variation factors in ruminants. Contrary to temperate grazing systems, tropical ones were poorly documented whereas weather or traditional grazing practices may change models established in temperate systems. The study was performed in the French West Indies, which are concerned by a widespread environmental chlordecone contamination. The work evaluated daily soil and grass ingestions by tethered growing bulls grazing on a very high sward close to 50 cm for 11 days without being moved. This grazing management is representative to local practices by small farmers or not professional holders and allows completing the results previously obtained. Daily soil ingestion did not significantly increase across time and was on average 26.9 g dry matter/100 kg body weight (i.e. 1.4% of the total mass ingested). Marked individual variations indicated that exposure risk assessments would require experimental designs based on a sufficient number of individuals. This study was also the first to investigate the changes in sward soiling with respect to the distance from the stake and reported lower soil loading on grass in the peripheral than central and intermediate areas.

PERENCANAAN PREFABRICATED VERTICAL DRAIN MENGGUNAKAN METODE ELEMEN UNTUK MEMPEROLEH POLA DAN JARAK YANG EFEKTIF

As a city develops, less areas will be available for constructions. Out of these available lands, a large quantity of areas has low soil bearing capacity and great amount of settlement. For this type of soil, loading is required in order to stabilize it. This will push out porewater contained inside the soil. However, reaching the expected settlement requires a long time, which can be solved by using prefabricated vertical drain to speed up the process. This is possible because prefabricated vertical drain decreases the travel distance of porewater to half of the vertical drain. Calculations for this thesis are done using one dimensional consolidation method, finite element method, and asaoka method for actual data calculation from the field. Using one dimensional consolidation method, with prefabricated vertical drain distance of 1.2 m in triangular pattern, resulted in settlement level of 2.048 m for 110 days. Using finite element method resulted in settlement level of 2.604 m for 120 days. On the other hand, using asaoka method resulted in settlement level of 1.422 m for 102 days. This difference is caused by lack of depth data from the laboratory.Semakin berkembangnya jaman maka pembangunan semakin banyak sehingga lahan untuk dilakukannya pembangunan semakin sedikit. Sekarang banyak tanah yang memiliki daya dukung kecil dan penurunan yang besar contohnya seperti tanah lunak. Agar tanah model ini dapat memiliki kondisi yang stabil , maka solusinya diberi beban sehingga air pori dari dalam tanah dapat tertekan keluar. Namun untuk mencapai penurunan yang diinginkan membutuhkan waktu yang cukup lama, disini digunakan metode prefabricated vertical drain untuk mempercepat penurunan. Prefabricated vertical drain disini membuat jarak tempuh air pori tanah yang sebelumnya setebal tanah lunak, menjadi setengah jarak antar prefabricated vertical drain. Perhitungan analisa pada skripsi ini menggunakan metode one dimensional consolidation, metode elemen hingga, dan metode asaoka sebagai perhitungan hasil aktual dari data lapangan. Penurunan total menggunakan metode one dimensional consolidation dengan jarak antar prefabricated vertical drain 1.2m dengan pola segitiga sebesar 2.048 m selama 110 hari, sedangkan dari metode elemen hingga didapatkan penurunan sebesar 2.604 m selama 120 hari. Dari data settlement recording yang dihitung menggunakan metode asaoka terjadi penurunan sebesar 1.422 m selama 102 hari. Perbedaan disini disebabkan oleh kurang banyaknya sample kedalaman dari data laboratorium.

Numerical techniques for design calculations of longitudinal bending in buried steel pipes subjected to lateral Earth movements

This paper presents simplified finite-element analysis procedures based on geometrical nonlinearity and ductile Mohr–Coulomb–Davis plasticity for analysis of bending behaviour of steel pipes subjected to lateral soil loading. A simple, and easy to implement, user-defined subroutine to represent soil stiffness using the Janbu model is also presented and discussed. The development of a three-dimensional (3D) finite-element model is presented, and its evaluation against experimental measurements is discussed. Data are presented for different burial depths of the pipe, including soil loading on the pipe as well as 3D responses, longitudinal bending deflections and pressure distribution along the pipe. It was shown that numerical analyses which include soil modulus dependency on confining pressure lead to effective 3D calculations of pulling forces, bending moments along the pipeline and flexural deformations, based on measured soil parameters. The 3D analysis model requires the use of lower order (linear displacement) elements, which overestimated peak mobilized load. However, those 3D calculations effectively provided the progress of both the load–deflection and longitudinal bending response of the steel pipe at embedment ratios up to 5 where most energy pipelines are buried.