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Soil

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Soil Test, Masalah dan Aplikasinya pada Tanah Lunak
Ir. Muhrozi, MS
Lab. Mekanika Tanah Jurusan Teknik Sipil Universitas Diponegoro

Pendahuluan Keberhasilan pelaksanaan suatu proyek sangat ditentukan oleh : input data (data penyelidikan tanah) dengan ketelitian yang tinggi, perencanaan (dokumen kontrak/gambar) yang mantap, dan pelaksanaan konstruksi dengan metode kerja yang tepat serta kontrol/pengawasan pada saat pelaksanaan dilakukan secara ketat. Pada akhir-akhir ini banyak masyarakat umum yang menanyakan kepada kita (orang sipil) dengan nada heran dan menyindir sebagai berikut : mengapa akhir-akhir ini banyak bangunan sipil yang runtuh dibanding dengan masa lalu (zaman Belanda) ?, padahal insinyur di Indonesia sekarang sangat banyak. Pertanyaan yang agak menyindir tersebut perlu kita sikapi dengan bijak, instrospeksi kepada diri kita masing-masing dan sambil mencari beberapa penyebab yang aktual, sehingga kita dapat mencari jawaban/solusi yang tepat untuk perbaikan masa yang akan datang. Menurut Penulis, penyebab banyaknya kegagalan konstruksi bangunan sipil pada akhir-akhir ini disebabkan oleh eksploitatifnya pemanfaatan tanah yang melebihi daya dukung tanah secara umum, sebagai contoh : pemanfaatan lahan gambut/rawa/tambak untuk perumahan dapat menyebabkan penurunan yang berlebihan, pembangunan jalan raya dengan timbunan yang melebihi tinggi kritis (Hcr) dapat menyebabkan sliding atau kelongsoran, timbunan optrit yang tinggi mengakibatkan dorongan pada abutment dan penurunan yang melebihi batas. Pemanfaatan lahan perbukitan dan lereng yang cukup terjal untuk pemukiman yang dikembangkan oleh developer / pengembang pada akhir-akhir ini dapat menyebabkan kelongsoran tanah, menambah debit banjir di daerah bawah dan mengganggu ekosistem tata air secara menyeluruh. Untuk memperkecil permasalahan-permasalahan tersebut diatas perlu didukung dengan “Kontrol Soil Test” yang memadahi dan teliti pada saat

perencanaan dan pelaksanaan, sesuai dengan judul makalah seminar yang diminta oleh BPPS HMSFT Univ. Diponegoro. Pada kesempatan ini kami ingin menginformasikan kepada peserta seminar, bahwa yang dimaksud dengan perencanaan bangunan bawah (sub struktur/pondasi) harus dimulai dari tahap Feasibility Study, tahap Perencanaan (Detail Desain), tahap Pelaksanaan (Construction) dan tahap Pasca Pelaksanaan sebagai monitoring. Hal ini perlu kami sampaikan mengingat banyak persepsi yang keliru, dimana pada pelaksanaan, desain pondasi dianggap sesuatu yang pasti dan tidak boleh dirubah seperti : dimensi struktur beton atau struktur baja. Hal tersebut dapat terjadi mengingat kompleknya faktor-faktor yang mempengaruhi kemampuan daya dukung tanah seperti : heterogenitas lapisan tanah dan struktur tanah, mudah berubahnya/melapuknya struktur lapisan tanah akibat gaya-gaya luar seperti : air, udara dan iklim. Untuk hal tersebut maka kontrol soil test harus dimulai dari Feasibility Study, Detail Desain dan pelaksanaan proyek (construction). Mengingat banyaknya macam penyelidikan, tanah dari mulai yang sederhana sampai yang sangat kompleks dan kegunaan dalam rekayasa bangunan Teknik Sipil maka dalam kesempatan ini akan diuraikan sebagian dari penyelidikan tanah yang sering dilakukan dalam pelaksanaan proyek, baik berskala kecil maupun besar. Penyelidikan Geoteknik Untuk dapat melakukan analisis Geoteknik (Mekanika Tanah dan Teknik Pondasi) yang benar dan baik, sangat diperlukan data-data tanah (soil test) bawah permukaan yang lengkap dan akurat. Data-data ada yang diperoleh langsung dari survey geoteknik lapangan dan ada yang diperoleh langsung dari uji laboratorium terhadap contoh tanah yang diambil dari bawah permukaan melalui boring. Penyelidikan tanah dilapangan dapat berupa penggunan dan interpretasi foto udara dan remote sensing, metode geofisik, metode geolistrik, sumur uji (test pit) pemboran (boring) (dangkal sampai dalam), uji penetrometer (uji sondir, Cone Penetration Test –CPT), uji Vane Shear Test, Pocket Penetometer Test, California Bearing Test (CBR) dan lain lain. Pemboran tanah/boring dan sondir (CPT) adala h pekerjaan yang paling umum dan akurat untuk tanah berlempung dalam survey geoteknik lapangan. Yang dimaksud dengan pemboran tanah adalah membuat lubang kedalam tanah dengan menggunakan alat bor manual maupun alat bor mesin dengan tujuan :

§ § § §

Mengidentifikasi jenis tanah sepanjang kedalaman lubang bor. Untuk mengambil contoh tanah asli maupun tidak asli pada kedalaman yang dikehendaki. Untuk memasukkan alat uji penetrasi baku (Standart Penetration Test, SPT) pada kedalaman yang dikehendaki. Untuk memasukkan alat uji lainnya kedalam tanah yang dikehendaki, misalnya : uji rembesan lapangan, uji vane shear, uji presuremeter, pengukuran tekanan air pori dan lain-lain.

Para peneliti geoteknik telah banyak membuat studi tentang hasil SPT untuk membuat korelasi dengan hasil uji lapangan yang lain, dengan berbagai sifat tanah, seperti jenis-jenis tanah dan konsistensinya, dengan kekuatan geser tanah, parameter konsolidasi, relatif density, daya dukung pondasi dangkal, daya dukung pondasi dalam, tiang bor dan lain-lain. Pekerjaan sondir (Dutch Cone Penetration Test, CPT) merupakan alat penyelidikan tanah yang sangat sederhana dan populer di Indonesia. Dari alat sondir, memberikan tekanan konus (qc) dan hambatan pelekat (fs) yang dapat dikorelasikan terhadap parameter tanah yang lain seperti : undrained shear strength (Cu), kompressibilitas (Cc), elastisitas tanah (Es) dan dapat memperkirakan jenis lapisan tanah dan parameter tanah lainnya. Sampai sekarang ini, hasil uji sondir untuk tujuan-tujuan seperti : § Evaluasi kondisi tanah bawah permukaan di lapangan, stratigrafi (menduga struktur lapisan tanah), klasifikasi lapisan tanah, kekuatan lapisan tanah dan kedalaman lapisan tanah keras. Menentukan lapisan tanah yang harus dibuang dan diganti dengan tanah yang lebih baik dan dipadatkan dan kontrol kepadatan tanah timbunan. Perencanaan pondasi dan perhitungan settlement. Perencanaan stabilitas lereng galian atau timbunan dan lain-lain.

§

§ §

Penyelidikan tanah di laboratorium yang umum dilakukan adalah: sifat fisik tanah (w, γ, e, n, Gs, Sr), sifat plastisitas tanah (LL, PL, PI, SL, SI, Ac,LI), sifat consolidasi tanah (mv, Cc, Cr, Cs, Ca, Cv, Pc), sifat kuat kuat geser tanah (c, ϕ , c’ , ϕ’ , Su, qu, St, Es), sifat copaction tanah timbunan (γ mak., OMC, CBR, Rd).

Hasil survei lapangan dan uji laboratorium tersebut dimaksudkan untuk dipakai sebagai input disain pondasi, timbunan tanah dan rekayasa bangunan sipil bagian bawah, untuk lebih mudah dan praktisnya kegunaan data tanah terhadap perencanaan pondasi dapat dibuat diagram secara singkat sebagai berikut :
Penyelidikan Tanah Soil Test

Lapangan

Laboratorium

Contoh Tanah

Undisturbed

Disturbed

Sondir - qc - JHP - fr

Uji Penetrasi - Nspt

Vase Shear - Su - Cu

CBR/ DCP - CBR

Kuat Geser - C,φ - C’,φ’ - Su,Es

Konsolida si - Cc - Cv,Pc - mv

Drainase -k - hc

Sifat fisik - w,γ - Sr,e - Gs,n

Gradasi/bu tiran - D10 - Cu,Cc

Plastisitas - LL,PL - PI,SL

Kepadatan - γmaks - OMC - CBR

Perhitungan
Daya dukung tanah Daya dukung pondasi -

Perhitungan Penurunan tanah Penurunan pondasi -

Menentukan Klasifikasi tanah Bentuk/jenis pondasi

Gambar detail desain dan spesifikasi teknik

Penentuan Letak dan Banyaknya Titik Bor dan Sondir

Untuk menentukan letak dan banyaknya titik bor dan sondir suatu proyek banyak ditentukan oleh : jenis dan karakteristik sruktur bangunan atas yang direncanakan, keanekaragaman sruktur geologi dan kondisi topografi daerah setempat, serta lokasi atau daerah yang dianggap kritis. Pedoman penentuan letak dan banyaknya bor dan sodir belum ada acuan yang jelas/pasti, dari berbagai sumber yang pernah kami dapat dapat disimpulkan sebagai berikut : a. Untuk proyek baru yang luas, untuk survey pendahuluan jarak titik bor dan sondir antara 50 m sampai 150 m satu dengan yang lainnya. Sedangkan pada survey detail penentuan titik-titik bor dan sondir harus dilakukan pada bangunan yang berat dan penting. b. Untuk sruktur yang besar dengan jarak kolom dekat, tempatkan titik-titik bor dan sondir berjarak 15 – 25 m, utamakan meletakkan titik bor dan sondir pada kolom yang bebannya berat, lokasi shearwall, lokasi ruang mesin dan sebagainya. c. Bangunan Jembatan, tempatkan titik bor dan sondir ditengah/sekitar perletakan pondasi, jika tanah diragukan perlu dilakukan pemboran kearah keliling pondasi. Pada timbunan oprit jembatan yang tinggi dan lebar, minimal dilakukan 1 (satu) titik bor dan sondir. d. Bangunan Gedung atau pabrik yang luas dengan beban kolom ringan sampai sedang, penempatan titik bor dan sondir cukup pada ke-empat sudut ditambah satu titik ditengah. Sedangkan untuk beban kolom berat dan daerah pantai perlu ditambah titik sondir dan boring. e. Bangunan berat di tepi laut, seperti dry dock yang sudah ditentukan letaknya, letakkan titik bor dan sondir berjarak 15 meter, dan tempatkan titiktitik bor pada daerah kritis dan rawan erosi. f. Rencana tembok penahan tanah yang panjang, tempatkan titik bor dan sondir masing-masing berjarak 60 m sepanjang alinemen dinding, dan tambahkan 2 (dua) titik bor atau 2 (dua) titik sondir diluar rencana dinding pada daerah yang dianggap kritis dan rawan longsor. g. Stabilitas lereng galian dalam (deep cut) atau lereng urugan yang tinggi (high embankment), minimal diperlukan 3 (tiga) titik bor pada titik kritis, sehingga dapat diperoleh potongan geologis yang baik untuk dianalisis, perlu diperlukan beberapa potongan geologis yang disesuaikan dengan kondisi geologi setempat. h. Perencanaan Bendung atau bendungan, tempatkan titik-titik bor berjarak 60 m sepanjang daerah rencana pondasi, kemudian tambahkan titik-titik bor

pada tempat yang kritis, seperti pada rencana spillway, pintu air, terowongan dan sebagainya, sehingga jarak titik bor menjadi 30 m. i. Rencana dermaga pelabuhan, jetty dan trestle, paling sedikit diperlukan 3 titik bor pada rencana jetty, satu titik bor pada rencana mooring dolphin, dan 2 titik bor yang berjarak 50 sampai 200 m pada rencana trestle. Meskipun sudah ada acuan tersebut diatas dan sumber-sumber yang lain, penentuan akhir letak dan jumlah titik boring dan sondir tergantung dari tenaga akhli geoteknik yang bersangkutan dan tergantung dari pengalaman yang apernah dilakukan. Hal yang terjadi adalah dibatasi oleh anggaran biaya yang tersedia. Kelebihan dan Kekurangan Uji Sondir dan Bor Uji sondir merupakan alat yang sederhana, praktis, dengan kelebihan yaitu : cepat, murah, menghasilkan data yang akurat dan detail. Sondir sangat cocok untuk tanah di Indonesia karena kondisi tanah di Indonesia sebagian besar berupa lempunga lanauan. Sedangkan kekurangannya adalah : tidak dapat diperoleh sampel, untuk uji laboratorium maupun untuk klasifikasi visual, dan tidak dapat menembus lapisan batuan. Untuk daerah-daerah tertentu dimana lapisan tanah berupa pasir maka alat ini kurang representatif dan tidak dapat menembus lensa gravel/pasir yang cukup tebal dan padat, sehingga bila dibawah lensa pasir terdapat tanah lunak maka sulit untuk terdeteksi. Pada tanah pasir pengaruh tekanan air pori selama penetrasi pada kecepatan penetrasi yang normal sangat kecil dan diabaikan, sehingga hasil sondir dalam keadaan fully drained, sedangkan pada tanah lempung plastis hasil uji sondir lebih kearah fully undrained dan bila jenis tanah diantara kedua jenis diatas dapat memberikan hasil untuk keadaan fully drained dan fully undrained. Uji bor merupakan pengujian lapangan yang paling baik dan akurat untuk segala jenis tanah dan diperlukan untuk test-test yang lain, sedangkan kerugiannya adalah : mahal, berat (perlu alat angkut yang memadahi), waktu pelaksanaan lama dan kurang cocok untuk bangunan sederhana. Setiap pelaksanaan test boring selalu diikuti dengan uji penetrasi baku (SPT), yang perlu diperhatikan adalah faktor-faktor yang mempengaruhi harga N-SPT yaitu : § Jumlah energi yang mencapai sampler, ditentukan oleh : jenis hammer, jenis dan panjang rod, variasi tinggi jatuh palu, jumlah lilitan tali dan umur tali.

§

§

Kondisi tegangan tanah dasar lubang bor bor, ditentukan oleh : kelalaian menjaga tekanan hidrostatis, tinggi air diluar dan didalam harus sama; metode pengeboran dan stabilisasi dinding, serta diameter dinding. Faktor-faktor ain, seperti : pembersihan dasar lubang bor, kelalaian menghitung jumlah tumbukan dan pemakaian sampler yang sudah rusak.

Interpretasi dan Analisis Data Tanah dari Lapangan dan Laboratorium Hasil eksplorasi (survey) geoteknik lapangan dan pengujian tanah di laboratorium merupakan data asli yang perlu di interpretasi dan dianalisis untuk disajikan sebagai penunjang pekerjaan desain, dan dibuat secara ringkas dan mudah dimengerti oleh pemakai data sesuai dengan tujuannya. Hal-hal yang perlu dimasukkan dalam analisis dan interpretasi dalam penyajian data adalah : § § § Asal usul batuan yang diteliti/diselidiki, disini perlu menelaah tentang geologi regional, stratigraphi, historegical dan lainnya. Interpretasi masing-masing log borhole perlapisan tanah, dikaitkan dengan jenis dan klasifikasi tanah secara Unified maupun AASTHO. Membuat profil lapisan tanah dari log borehole satu ke log borhole yang lain, sehingga dapat ditentukan pemetaan per lapisan tanah yang sejenis, pada potongan melintang yang dikehendaki. Membuat tabulasi atau ringkasan hasil soil test yang dilakukan seperti : summary of field vane shear test, summary of field permeability test, summary of chemical analysis, summary of soil stratigraphy, summary of soil properties, dan lain-lain yang perlu. Membuat rekomendasi masing-masing parameter tanah yang dihasilkan dari test laboratorium dan dibandingkan dengan parameter tanah yang dihasilkan secara empiris dari hasil test sondir dan N spt maupun yang dikaitkan dengan parameter lainnya. Menyajikan kapasitas daya dukung tanah dan daya dukung tiang secara umum. Rekommendasi dan saran-saran pada saat perencanaan maupun pelaksanaan.

§

§

§ §

Rumus-rumus yang Sering Dipakai untuk Pondasi & Pekerjaan Tanah 1. Kapasitas Daya Dukung Tanah (Terzaghi) Pondasi menerus → q ult. = C.Nc + γ.D.Nq + 0,50. γ.B.Nγ Pondasi persegi panjang → q ult. = 1,3.C.Nc + γ.D.Nq + 0,40. γ.B.Nγ Pondasi lingkaran → q ult. = 1,3.C.Nc + γ.D.Nq + 0,30. γ.B.Nγ dengan Nc,Nq dan Nγ adalah faktor daya dukung tanah (ditentukan dari besarnya φ) 2. Tinggi Timbunan Kritis (Hcr) Untuk tanah dalam kondisi jenuh Cu . Nc H cr = γ timbunan dengan besarnya Nc → → → → Fellenius (1921) = 5,50 Terzaghi (1943) = 5,70 Atkinson (1980) = 6,00 cohesion undrained

Cu

3. Penurunan Tanah akibat adanya tambahan beban Cc Po + ∆P H.log 1 + eo Po S = H . mv . ∆P 1 1 Po + ∆P St = H { + . log t to } . ln Cp Cs Po S= 4. Stabilitas Lereng Cu Cara Taylor → FK = Ns . ã . H dengan : Ns = ditentukan berdasarkan φu (sudut geser dalam tanah) dan sudut kemiringan tanah (β) → lihat diagram Taylor’s stability coef. H = tinggi timbunan / galian tanah Metode Potongan (Fellenius Solution) C' La + tan φ' ∑ (W . cos α - u l ) ∑ W sin α → tanpa perkuatan geotextile

FK =

FK =

C' La + tan φ ' ∑ (W . cos α - u l) + ∑ Ti . Yi → dengan perkuata n geotextile ∑ W sin α

5. Rumus-Rumus Empiris Dengan Data Sondir a. Pondasi Dangkal § Tanah Berpasir L’Helminier (1953) → q all. = qc / 10 Sanglerat (1972) Mayerhof (1965) § → q all. = (B. qc / 40) x (1 + B/D) → q all. = (qc/50) x (1 + 0,3/N) 2

Tanah Berlempung Prandti (1921) → q all. = (0,05 . qc . Nk) / 2,50 + γ D dengan : Nk = faktor konus (tergantung dari jenis tanah)

b. Pondasi Dalam § Cara Mayerhof (1956) P ult. = qc . Ab + fs . As dengan Ab = luas dasar pondasi As = panjang keliling pondasi qc = qc rata-rata, sepanjang 4 diameter bagian atas rencana ujung tiang dan 1 diameter dibawah ujung tiang fs = qc / 200 < 1 kg/cm’ → tiang beton fs = qc / 400 < 1 kg/cm’ → tiang baja

§

Cara Beggeman P all = qc . Ab JHP . As + 3 5

dengan

qc = ½ (qc-u + qc-b) qc-u = qc rata-rata sepanjang 8 diameter bagian atas ujung tiang qc-b = qc rata-rata sepanjang 3,5 diameter bag. bawah ujung tiang

6. Rumus-Rumus Empiris Dengan Data Nspt a. Pondasi Dangkal § Teng (1962) mengusulkan pemakaian rumus empiris sebagai berikut → Pondasi bujur sangkar q ult. = 2.Nspt. 2.B.Rw + 6(100 + Nspt.).D.Rw’ → Pondasi menerus q ult. = 3.Nspt. 2.B.Rw + 5(100 + Nspt.).D.Rw’ dengan N spt. = Nilai Nspt. Rw,Rw’ = Faktor koreksi muka air tanah § Terzaghi & Peck (1948) memberikan formula yang menghubungkan nilai Nspt. dengan daya dukung ijin tanah pasir untuk setlemet sebesar 1”, sebagai berikut : q ult. = 720 (Nspt. – 3) × ((B + 1) / 2B) 2.Rw’ dalam satuan (psf) Parry (1977) menentukan daya dukung batas tanahnon kohesif sebagai berikut : q ult. = 30 Nspt. ( Kpa ) → untuk Df < B

§

b. Pondasi Dangkal § Mayerhof (1956) mengusulkan formula untuk menentukan daya dukung tiang pancang pada lapisan pasir sebagai berikut : Q ult. = 40.Nb.Ab + 0,20 N rt . As dengan Q ult. = Daya dukung pondasi batas tiang pancang (ton) Nb = Nilai N spt. pada dasar pondasi Nrt = Nilai N spt. rata-rata

§

Schemermann (1967) mengusulkan formula untuk menentukan daya dukung tiang pancang dengan penurunan kecil sebagai berikut :

Q ult. = 40 Nb . Ab + 0,10 N rt . As Dengan harga batas → Nb = 40 dan 0,10 N rt = 5 ton/m2 § Cara Japan Road Association (1976),

Referensi : R.F Craig, 1987, Soil Mechanics, Van Nostroad Reinhold (UK) R.L Mitchell, Earth Structures Engineering, 1983. Hans F. Winterkom dan Hsai-Yang Fang, 1975, Foundaiton Engineering Handbook, Van Nostroad Reinhold. Hasil Penyelidikan Tanah Jalan Lingkar Utara Section 03 paket 01 yang dilakukan oleh Lab. Mek Tanah UNTAG Semarang, Lab. Mek Tanah UNDIP, Lab Mek. Tanah UNISSULA Semarang. Evaluasi Geoteknik Jalan Lingkar Utara Semarang, STA. 0+00 - STA. 3+00 Proceedings Konperensi Geoteknik Indonesia IV, HATTI, Bandung, 2-27 Februari 1990. Hasil Penyelidikan Tanah Tangki Minyak PLTGU Tambak Lorok Semarang. Seminar Pembuatan Jalan Diatas Tanah Lembek, Jakarta, 25-26 Juni 1986.

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...Soil Conservation Working Group Report This report provided content for the Wisconsin Initiative on Climate Change Impacts first report, Wisconsin’s Changing Climate: Impacts and Adaptation, released in February 2011. THE WISCONSIN INITIATIVE ON CLIMATE CHANGE IMPACTS 1st Adaptive Assessment Report Contribution of the Soil Conservation Working Group July 2010 Contour stripcropping in central Wisconsin Photo by Ron Nichols, USDA Natural Resources Conservation Service Participants of Working Group William L. Bland, Professor, Department of Soil Science, University of Wisconsin-Madison (Working Group Chair and lead author) Kelly R. Maynard, M.S. Agroecology, University of Wisconsin-Madison (Project Assistant) Jeremy Balousek, P.E., Urban Conservation Engineer, Dane County Land and Water Resources Department Denny Caneff, Executive Director, River Alliance of Wisconsin, Inc. Laura W. Good, Associate Scientist, Department of Soil Science, University of Wisconson-Madison Kevin Kirsch, Water Resource Engineer, Wisconsin Department of Natural Resources Patrick Murphy, State Resource Conservationist, Natural Resources Conservation Service John M. Norman, Emeritus Professor of Soil science, Department of Soil Science, University of Wisconsin-Madison James VandenBrook, Water Quality Section Chief, Wisconsin Department of Agriculture, Trade, and Consumer Protection Sara Walling, Water Quality Specialist, Wisconsin Department of Agriculture, Trade, and ...

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Soil Investigation

...Soil investigation is often neglected or rejected by most clients on the basis of cost, despite the fact that the cost of carrying out a soil investigation is very little compared to the cost of the project Soil investigation is done for various purposes. In engineering, soil investigation is very necessary. It is essential to investigate the soil of the selected plot on which a structure will be constructed. Based on soil investigation a soil report is prepared for the purpose of designing the building foundation. When an engineer designs building foundation he/she must carefully read the report and design the foundation based on the data provided in the report. Soil investigation is required for the following purposes - To know the allowable bearing capacity of foundation for proposed building. To know the depth and type of foundation for the proposed building. To know the allowable passive resistance for the foundation of proposed building. To know the type, grading and nature of soil. To know the ground water level. Typical steps of soil investigation Soil investigation involves following steps –  Details planning for the sequence of operations.  Collecting the samples of soil from the plot.  Determining the soil characteristics by conducting field tests.  Study the condition of ground water level.  Collecting ground water sample for chemical analysis.  Soil exploration.  Testing all collected samples in the laboratory.  Preparation of drawings...

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Soil and Glacier

...University of Phoenix Material Soil and Glaciers Worksheet From Visualizing Earth Science, by Merali, Z., and Skinner, B. J, 2009, Hoboken, NJ: Wiley. Copyright 2009 by Wiley. Adapted with permission. Part 1 Size grades of soil are named sand, silt, and clay, which includes colloids. Size grades are defined using the metric system. Use Figure 4.8 from the textbook to fill in the following chart. Specify the type and size and description of the particle. In some cases, particle size will be less than some value or greater than another value. For instance, gravel is greater than 2.0 mm. Name Size Description Gravel >2.0 mm Rock that is unconsolidated with fragments that have a general particle size range Sand 0.05 Sand particles are largerly formed by the physical break up of rocks. Sand has small surface areas and have an almost negligible role in the chemical activity of the soil. Sand particles are chemically insert or inactive. Silt 0.002 Silt is formed by physical weathering. Finer silits, which approach colloidal sizes, may exhibit some of the characteristics properties of clay. Clay Below 0.002 milimeters The clay fraction differs from the sands and silts in that it is composed predominantly of minerals formed as products of secondary weathering. The rock mineral will go through change before becoming clay minerals. Colloids 0.0001 – 0.00001 milimeters Like other soil particles, some colloids are minerals, whereas others are organic. Minerals colloids...

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Soil and Glaciers

...University of Phoenix Material Soil and Glaciers Worksheet From Visualizing Earth Science, by Merali, Z., and Skinner, B. J, 2009, Hoboken, NJ: Wiley. Copyright 2009 by Wiley. Adapted with permission. Part 1 Size grades of soil are named sand, silt, and clay, which includes colloids. Size grades are defined using the metric system. Use Figure 4.8 from the textbook to fill in the following chart. Specify the type and size and description of the particle. In some cases, particle size will be less than some value or greater than another value. For instance, gravel is greater than 2.0 mm. |Name |Size |Description | |Gravel |>2.0 mm |Gravel is very small, irregular pieces of rock and stone. Gravel is more rough and rocky than sand, and | | | |smaller than stones. The word gravel comes from the French word gravele, "gravel or sand," which in turn | | | |comes from grave, "seashore or sand ("Gravel ", 2015). | |Sand |0.05 |sedimentary material, finer than a granule and coarser than silt, with grains between 0.06 and 2.0 | | | |millimeters in diameter ("Sand", 2003-2015). | |Silt |0.0002 |Silt is very...

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Soil Science

...CHAPTER 1 1. INTRODUCTION Rice is one of the important food crops in the world, and it is the staple diet of 1.6 billion people in Asia. Average yield of rice in Malaysia is 3.2 t/ha which is low compared to an average of 5.4 t/ha from East Asian countries. Nowadays, people tend to eat more quality foods rather than normal food. An example, most of people will choose the healthy one likes organic rice; Brown Rice. Therefore, in order to handle these situations our government suggests to all farmers to handle the natural farming at their farms. Natural farming is one of the production methods that use the organic crops such as Indigenous Microorganisms, fertilizer and some factors likes air, water and soil. In additions, large sums of money have been invested in providing irrigation and drainage infrastructure facilities to enable double cropping of rice using high yielding varieties with the latest agronomic practices in attempts to attain high rice yields. There is an alarming concern of a future demand for still higher levels of chemical to be used in order to maintain crop yields. Apart from this, the excessive dependence on chemical pose health hazards and are harmful rice agro-ecosystem and methods to sustain yield levels with the minimal use of chemicals. How to find the solutions? For the detail solution we are explain in this report. In this report, we include the best management practices that can be applied in natural...

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Soil Erosion

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Soil Properties

...The purpose of a site investigation is to identify the ground conditions which might affect the proposed development. It enables better understanding of the site and immediate surroundings, which will enable safe and economic developments. They are a common requirement of the investors as well as the regulatory authorities. In the broadest sense, the ground conditions are understood to include not only the underlying soils and rocks but also the groundwater regime, any contamination and effects of any previous uses of the site The purpose of a site investigation is to identify the ground conditions which ma, any contamination and the effects o 1.1.1 The scale of problem Various reports over the past 25 years have shown that the largest element of technical and financial risk normally lies in the ground. Ground related problems have led to late completions and high cost overruns on the national scale. Lady using a tablet Professional Essay Writers Get your grade or your money back using our Essay Writing Service! ESSAY WRITING SERVICE In an analysis of 8000 building projects, National economic Development office (NEDO) stated that one third of the projects overran by more than a month, a further one third overran up to a month due to delays due to unforeseen ground conditions. Work in groups or pairs, note down a few points on Why carry out site investigation? 1.2 Why carry out site investigation? The characterization of ground conditions whether for...

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Soil Horizon

...A soil horizon is a layer generally parallel to the soil surface, whose physical characteristics differ from the layers above and beneath. Each soil type usually has three or four horizons. Horizons are defined in most cases by obvious physical features, chiefly colour and texture. These may be described both in absolute terms (particle size distribution for texture, for instance) and in terms relative to the surrounding material (i.e., "coarser" or "sandier" than the horizons above and below). The differentiation of the soil into distinct horizons is largely the result of influences, such as air, water, solar radiation and plant material, originating at the soil-atmosphere interface. Since the weathering of the soil occurs first at the surface and works its way down, the uppermost layers have been changed the most, while the deepest layers are most similar to the original parent material. Identification and description of the horizons present at a given site is the first step in soil classification at higher levels, through the use of systems such as the USDA soil taxonomy or the Australian Soil Classification. The World Reference Base for Soil Resources lists 40 diagnostic horizons.[1] Soil scientists often dig a large hole, called a soil pit (usually several meters deep and about a meter wide) to expose soil horizons for study. The vertical section exposing a set of horizons, from the ground surface to the parent rock, is termed a soil profile. Most soils, especially...

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Essay On Geography Of Soil

...Maeve Upton 14310368 C. ‘In order to understand the geography of soil all one needs is a good map of the solid geology.’ Abstract: It would be naïve to assume that a good map of solid geology is the only resource needed to understand the geography of soils. The geography of soil does not depend solely on the solid geology of the biosphere and lithosphere. When one studies the geography of soil it is important to look at the properties of soils including the parent material which is usually the dominating underlying bedrock. However, one must take into account the factors that affect soil development and the processes in soils that can produce variations. For examples, climate, topography, time, biological agents such as animals and human interference. Pedology provides us with a soil classification system that can be used to determine types of soil but throughout history it has been...

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Essay On Soil Erosion

...Soil erosion poses a significant threat to the environment and agriculture. The repeated loss of fertile topsoil negatively affects the long term sustainability of natural systems. Agricultural productivity faces a significant decline as a result of soil erosion Kusimi et al., (2015). Agricultural land across the world has either been lost or is rapidly experiencing degradation as a result of soil erosion. According to Arekhi et al., (2012), close to 40% of the world’s agricultural land is degraded, this includes 65% for Africa, 74% and 45% for North and South America respectively. Notable is that soil loss by erosion is an ongoing process, it was earlier reported by (Dudal 1981) that, across the globe , approximately 6,000,000 ha of fertile...

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Soil Protection in South Africa

...Soil Protection in South Africa. Soil protection is the protection and management of the quality of soil. It is all about solving the problems of land degradation. It can further be defined as the combination of the appropriate land use and management practices that promote the productive and sustainable use of soils and in the process minimise soil erosion and other forms of land degradation. 3.2.10 Causes of soil degradation in South Africa. Erosion. Erosion is the detachment and transportation of soil materials by wind or water. Soil erosion is a major problem of agriculture in South Africa. Soil erosion is a natural process but it becomes a serious problem when the activities of humans accelerate the process of its occurence. Land degradation caused by soil erosion causes the loss of fertile topsoil and reduces soil productivity. Researches have shown that over 70% of the soil in South Africa has been affected by one form of soil erosion or the other. The annual soil loss due to soil erosion in South Africa is estimated at 300 – 400 million tonnes for each hectare of land. South Africa loses an average of 20 tonnes of soil for each tonne of agricultural products produced. Soil erosion can be caused by water and, or wind. The effects of these factors on the soil are determined by the speed and the soil cover at the time of occurence. It is estimated that 25% of the country is covered by soil that is susceptible to wind erosion. These include the sandy soils in the...

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