ISBN No. : 978€02-17221-1-4
HIMPUNAhI AHLI TEKNIK TANAH INDONESIA INDOtIESIAN SO(;lETY FOR GEOTECHNICAL ENGINEERING (ISGE) MEMBER SOCIEY OF INTERNAT]ONAL SOCIETY FOR SOIL MECHANICS AND GEOTECHNTCAL ENGTNEERTNG {TSSMGE}
SffiArewwMWMw36W KGeotechnical Solution in Indonesia to Respond the Challenge of Urbano Industry, Infrastructure and Mining Developmentn'
IF{ \l
*"t-if r-.1li f
\ ? E{
..1.
.' .'.;
.. ..*::'.'-:'ir
&i&4'":iT:: Y
Proceedin g
l7'' Annual Scientific Meeting
Jakarta, l3-14 November 2013
('Geotechnical
Solution in Indonesia to Respond the Challenge of Urban, fndustry, Infrastructure and Mining Developmenttt
Editor
:
Hasbullah Nawir Bigman Marihat Hutapea YP. Chandra
Widjojo Adhi Prakoso Hendra Jitno Agus Setyo Muntohar
HIMPUNAN AHLI TEKNIK TANAH INDONESIA INDONESIAN SOCIETY FOR GEOTECHNICAL ENGINEERING (ISGE) Basement Aldevco Octagon, Jl. Warung Jati Barat Raya No. 75 Jakarta Selatan 12740
I7tt' Annual Scientifc Meeting Jakarta. I 3-11 November 201 3
KATA PENGANTAR
Assalamulaikum Wr. Wb. Para undangan, para pengurus Pusat dan Daerah Himpunan Ahli Teknik Tanah Indonesia. para pembicara dan peserta Pertemuan Ilmiah Tahunan HATTI yang kami hormati, Pertemuan llmiah HATTI tahun ini mengambil tema .6Geotechnical Solution in Indonesia to Respond the Challenge of Urban, Industry, Infrastructure and Mining Development". Saat ini pemerintah dan swasta semakin giat melakukan investasi pada sektor konstruksi, baik
untuk bangunan pekantoran, apartemen, MRT, pelabuhan, jalan bebas hambatan maupun inlrastruktur untuk perlambangan. Hal ini berhubungan dengan program pemerintah clalam konteks percepatan pembangunan ekonomi Indonesia. Terobosan baru dalam meniawab masalah geoteknik berkembang semakin pesat dan menjadikan keterlibatan serta peran Geotechnical Engineers semakin penting. Selain mengangkat topik seminar yang berkaitan dengan aspek geoteknik dan perkembangan riset serta teknologi terbaru sebagai pendukungnya, PIT XVII inijuga menggelar Workshop
GROUND IMPROVEMENT FOR DIFFICULT SUBSOIL CONDITIoNS. Kegiatan seminar dan workshop ini diharapkan dapat memberi kesempatan kepada seluruh peserta untuk berbagi informasi dengan para praktisi konstruksi khususnya di bidane SAtu haTi tentang
geoteknik. Fada kesempatan ini, atas nama seluruh anggota panitia penyelenggara, kami meneucapkan terima kasih kepada GEOHARBOUR GROUP sebagai sponsor utama seminar dan trrirksht p Fertemuan
Ilmiah HATTI tahun 2013. Ucapan terimakasih juga kepada para pembicara.
penulis makalah, para sponsor dan para peserta yang telah berpartisipasi untuk suksesn\a PIT-XVII ini. Kami mohon maaf apabila dalam penyelenggaraan pertemLran ini eJa kekurangan yang tidak berkenan. Selamat berdiskusi dan semoga Pertemuan Ilmiah Tahunan perkembangan profesi Geoteknik di tanah air.
Wassalamualaikum Wr Wb, Panitia PIT - XVII
Dr. Ir. Wiwit nanayu Ketua
ini dapat bermant-aat
basi
Annual Scienti/ic Nleeling Jckarta, I 3-11 November 2013 l7'1'
SAMBUTAN KETUA UMUM Assalamu'alaikurn Wr. Wb. Salam Sejahtera bagi kita semua'
pembicara, dan saudara-saudara Bapak wakil Menteri, Bapak Dirjen, para undangan, para hormati, atas nama Pengurus saya peserta Peftemuan llmiah Tahunan XVII HATTI.yang pusat HATl'l saya ucapkan terima kasih atas kedatangan Bapak/lbu sekalian di acara ini' saya menyampaikan yang merupakan event tahunan HATTI. Secara khusus perkenankan Wakil Menteri Bapak kesediaan atas terima kasih dan penghargaan yang setinggi-tingginya ini' Tahunan perhubungan dan PU L.tuungkan waktu untuk menghacliri Pertemuan Ilmiah
"Geotechnical Solution in Hadirin yang saya hormati, dalam PIT kali ini diusung tema and Mining Indonesia to Responcl the Challenge of Urban, Industry Infiastructure 'l'ema ini diharapkan Japat mengantisipasi perkembangan yang makin pesat Development". Bagaimanapun' dan dibutuhkan pada sektor iniiastruktur dan pertambangan di lndonesia'
dengan konstruksi perkembangan kedepan akan membawa kita pada kebutuhan pembangunan jernbatan dan terowongan. Untuk dapat rnewujudkan ini, bagaimanapun
,kulu b"ruiseperti tidak dapat dihindari suatu tahap yang kritis dimana masalah-masalah geoteknik harus solusi yang diselesaikan terlebih dahulu. Para ahli geoteknik diharapkarr dapat memberikan dapat terbaik. Dalam kerangka inilah para ahli geoteknik dituntut untuk secara terus menerus di meningkatkan kompetensinya agar dapat mengikuti perkembangan dan kebutuhan lapangan.
HATTI yang saya cintai, perkenankan saya untuk mengingatkan kembali bahwa tahun 2015 tidak terasa semakin mendekat, dimana akan dimulai pasar bebas ASEAN. Mulai para anggota
tahun tersebut, pekerjaan jasa konstruksi termasuk geoteknik akan dipasarkan secara bebas di
seluruh negara-negara ASEAN, artinya setiap orang atau badan usaha akan memiliki kesempatan yang sama untuk memperebutkan lapangan pekerjaan geoteknik di negara-negara ASEAN termasuk di Indonesia.
para anggota HATTI yang saya cintai, sungguh akan sangat ironis apabila pekerjaan geoteknik di Indonesia justru dikerjakan oleh orang-orang bukan Indonesia. Adalah menjadi iunggung jawab kita semua untuk mempertahankan eksistensi profesi geoteknik di Indonesia sehingga mampu menjadi tuan rumah di negeri sendiri dan bukannya tamu di negeri sendiri. Oleh karena itu marilah kita persiapkan diri kita masing-masing dalam menghadapi pasar bebas ASEAN 2015 nanti. Sebagai penutup, saya ucapkan banyak terima kasih atas kehadiran Bapak/lbu semua' khususnya saya tujukan pada sponsor utama kali ini, GE,OHARBOUR, dan sponsor-sponsor lainnla ).ang telah turut berpartisipasi sehingga PIT ini dapat berlangsung dan berakhir denoan sukses dari mulai hari ini sampai besok. Selamat mengikuti PIT. ',\ :ss.rlamu'alaikum Wr. Wb. i.',.::;:. I -l \or ember 2013
"
-
\"1:s.':.'rir Irslanr. \{SE.. Ph.D
I7'h
Annual Scientific Meeling
Jakarta, I 3-14 November
201 3
Agus Darmawan 11.
Adi
Analisa Mikrotremor dengan Metode HVSR (Horizontal to Vertical Spectral Ratio) untuk Pemetaan Mikrozonasi di Kelurahan Kejawan Putih Tambak Surabaya Ria Asih Aryani Soemitro; Trihanyndio Rendy Satrya; Dwa Desa I4/arnana; Reza Agus Parlindungan Harahap; Laily Endah Fatmawati
12.
Application of 25 m Height of MSE Wall for Road Widening Rivai Sargawi; Endra Susila
13.
Research on Eartiquakes Induces Liquefaction in Padang and Yogyakarta
211-l1f
I I '-ll-l
Area Agus SetyoMuntohar.. 14.
Analisa Beban Gempa pada Dinding Besmen dengan Plaxis 2D Gouw TL, Ferry Aryonto, Irpan
15. Clay Stabilisation
16.
vlll
With Stillage for Subgrade Stabilisasi Tanah Lempung dengan Stillage untuk Lapisan DASAR TANAH Ibrahirn, Muhammad Ar.fan
ll-r-:.xt
Different Types of Ground Source Heat Pump and its Usage. GUNAIilA|V Anrhony ... ..
l+r-:::
I7'h Annual
Scientific Meeting
Jakarta, I3-11 November 20t3
4. 5.
Setianto Samingan Agus; Nicholas Mace
135-140
Studi Eksperintal Potensi Penggunaan BakteriBacillus Subtilis untuk Meningkatkan Kuat Geser Tanah Pasir Yustian Heri Suprapto; Wiwik Rahayu; Hussein Mroueh
141-146
Karakteristik Kimia, Fisis dan Mekanis Abu Sawit dalam Aplikasi Geoteknik Muhardi; Ferry Fatnanta; Rizqy Yuliana
147-152
Other Session
1. 2"
3. 4.
5"
6.
:
Application of Vacuum preloading Method in lndonesia Yu Liu
I
Some New Ground Improvement Techniqr_res in China Xiaoming Lou; Jihong Cu...
r59-r66
Perhitungan Praktis Perenca naan Pondasi Tiang Terhadap Beban Lateral Hadi Rusjanto Tanuwidj ajct
167
8" 9" 10.
-172
Sudut Keruntuhan Galian Vertikal dari Beberapa Skala pengamatan Berbeda
Herman Wahvudi
173-178
Studi Parametrik Perilaku MSEW Dengan Material Granular Terhadap Beban Dinarnik William Y. Sormin; Widjojo A. Prakoso
l7g_lg4
Power Spectrum Density of wavelet (psDw) Technique for Determining Attenuation Factor of Soil Structures. Sri Atmaja P.
7.
53-l 58
Rosyidi
l g5_ I92
Korelasi Hasil Uji Mackintosh probe dengan Kuat Geser Undrained dari pengujian Vane shear Lapangan Soewignjo Agus l+tugroho; Ferry Fatnanta; Rizka Safitrt ... ......
t9i-198
studi Eksperimental Potensi Likuifaksi di Kali opak Imogiri Daerah Istimewa Yogyakarta Lindung Zalbuin Mase; Teuku Fai,sal Fathani; Agus Darmawan Atli
199_l0l
Liquefaction Potential Analysis on Bantul Regency and yogyakarta Area Bonifacius Adiguna Yogatama; Teuku Faisal Fathani,
105_210
cin
Identifikasi potensi likuifaksi tanah untuk penyiapan pengembansan lahan
VII
r,l
:
L'-i-r,r-iir? k
dkk-Institut Teknologi Bandung
67-72
K.-rnparasi vs30 Berdasarkan Metode Downhole Seismik dan Metode
\I.\S\\'
:.
Il'icliojo A. Prakoso; I Nyoman Sukanta; Damrizal Damoerin
13-76
Pengembangan Metode Zonifikasi Penggunaan PondasiDangkal untuk Bangunan Sederhana Tahan Gempa Ria Asih Aryani Soemitro; Trihanyndio Rendy Satrya; Dwa Desa Warnano; Reza Agus Parlindungan Harahap
77 -84
Session
1 2.
3.
II
:
Impact of Wet-Dry Cycles to Shear Strength and Swelling Behavior in Expansive Clay Using Artificial Soil Yonathan Setiawan: Edwin Laurencis; Hasbullah Nowir........ .....
Individu Test Sistem Cakar Ayarn Modifikasi Pada Tanah Ekspansif Model Skala Penuh di Lapangan Bambang Setiawan; Hary Christady Hardiyatmo; Bambang Suhendro; AEys Darmawan Adi...
.
2.
s
ar
i,
I'{ur
ly
G
oft,
Metode dan Prosedur Analisis Hitung Balik Pada Kasus Kelongsoran Lereng R[vai Sargavti; Anton Junaidi
Session I
101- I 08
Shear Strength and Long Term Compressibility of TropicalPeat Yu I i n da
5,
9l-100
Bearing Capacity Improvement by Grid and Woven Bamboo Reinforcernent Ratna Dewi; Yulindasari Sutejo; Hanafiah...
4.
85-90
III
109-l l4
1
l5-120
:
Perfonnance of Storage Tanks Supported on Deep Vibro Techniques Leong Kam [4/eng; Hendy l'l/iyono; Giovanni Ahmad
121-t26
Experimental Study of Stabilization Expansive Clay Soils by Using Electrokinetics Process lrlahesson Hotmarama Panjaitan; Ahmad Rifu'I; Agus Darmawan Adi,' P. Sumardi
127
Design and performance of a reclamation work in Singapore
-134
Annual Scientific Meeting Jakarta. I3-14 November 201 3 I7'h
TABLE OF CONTEI.{TS Preface Committee Chairman Message from President of Indonesian Society for Geotechnical Engineering
(rsGE) .................. Organizing Committee
Iil
Table of Contents
tv
Keynote Speakers
I
Innovative Soft Soil Improvement Method through Intelligent use Vacuum De-Watering and Dynamic Compaction Techniques Prof. Robert Y. Liang, Prof. Tuncer B. Edil
2
"
2'
3" 4.
5.
of
Methods of soft ground treatment and rigid bored pile foundation for offshore structure. Mr. Thomas Domanski / Regional Manager, BAUER southeast Asia pacific
9qssion I
:
I
l-18
l9-34
:
The study of strip Footing Bearing capacity on Layered clay Soils Using "Meyerhof and Hanna" Method and Finite Element Method (plaxis Program) Arief Budi Parsatya; Aswin Lim,. Siska Rustiani lrawan
35-41
Pengaruh Pre-Boring pada Kapasitas Friksi Tiang pancang Bigman M Hutapea, Aksan Kawanda, Edwin Laurencis, Achmad Arifin, Abdi Pasya, Bagaskara Kusuma
4l -50
Kapasitas cabut Jangkar Pelat Tipe Bintang pada Tanah Kohesiv Abdul Rachman; Lawalenna Samang; A.M. Imran,.Achmad Bakri M..
5l-58
Estimasi Bearing Stratum untuk Desain pondasi riang dengan Menggunakan Geostatistik Ardy Arsyad, M. Ihdam, M. Iskandar ......
59-66
Pengembangan Peta Klasifikasi Tanah dan Kedalaman Bantuan Dasar untuk Menunjang Pembuatan Peta Mikrozonsi Jakarta Dengan Mengsunakan
Mikrotremor Arrav.
l7'h Annual Scientific
.lakarla, I 3-l
I
Meeting
Novemher 20 I 3
Shear Strength and Long Term Compressibility of Tropical Peat Yulindasari Sutejor 'Dos"n Jurusan Teknik Sipil, Fakultas Teknik, Universitas Sriwiiaya Jl. Raya Praburnulih KM 32 Indralaya, Sunratera Selatan, r-mail:
[email protected]
Nurtv Gofar
2
'Dosen Jurusan Teknik Sipil, Fakultas Teknik, [Jniversitas lndo Global Mandiri, Jl. Jend. Sudirman, No. 629, Km 4, Palembang, 30128, Sumatera Selatan, e-mail: nurrygof-ar@)rahoo.c'm
ABS'|RACT : Ahnost 1.5 million hectare (20.60 Yi) of South Sumatra is covered by peat overlaying soft cohesive soil. Thus, the knowledge on the compression behavior of peat soil is essentfal fbr the aesfun of infiastructures in the area. This paper discusses the shear strength and long tenn compression behavior of preat" 'lhe sheal strength is assessed by field vane shear test ancl laboratory direct shear test while the long trerm eompression behavior is analyzed based on data obtained frorn consolidation test perforrned in Rowe eell with excess pore water pressLrre measllrerlent. Study shorvs that the peat has very low shear strength indicated by low cohesion while the high internal friction angle was derived from the flber content. Fufthernore, the results indicate that the peat has a significant secondary compression stage which is not rj;onstant with the logarithmic of tin"re. The secondary compressic,n stafied as early as 65 oh degree of primary
t,lrnsolidation. The consolidation test with pore water pressure measllrement using Rowe cell enables the cbservation of the large deformation and better assessment olthe long term compression behavior of fibrous peat"
Keyrvords: peal, shear strenglh, contpression behavior, pore-v)a,ier pressure mec.tsLrrement
ABSTRAK : Hampir
1.5 jLrta hektar (20.60%) luas
propinsi Surnatra Selatan ditutupi oleh tanah garnbut di
atas tanah lernpung lunak. Oleh karena itu pengetalruan mengenai sifat kompresibilitas tanah gambut sangat periting bagi perencanaan infrastruktur di daerah ini. Artikel ini rnembahas kekuatan geser dan k-r.rnrpnesibilitas tanalr garnbut. Kekuatan geser diukr-rr dengan uji geser baling di lapangan dan uji geser
iangsung
di
laboratorium, sedangkan kornpresibilitas dianalisis berdasarkan hasil pengujian koniolidasi
rnenggunakan sel Rowe dengan pengr:kuran tekanan pori. Hasil str-rdi menunjukkan bahwa tanah mempunyai I<ekr-latan geser berupa kohesi yang sangat rendah dan sudr,rt geser dalam yang cukr-rp tingi yang disebabkan
oleh serat sehingga tidak dapat diperhitungkan. Kajian juga nrenunjukkan bahwa tanah gambut jenis ini rnernpunyai sifat rangkak yang dominan dan tidak linier terhadap waktu. Penyusutan akibat rangkak dirnulai seawal 65 o/o deraiat konsolidasi prirner. Pengujian dengan rnenggunakan alat konsolidasi Rorve dengan pengukuran tekanan air pori sangat berguna karena memr-rdahkan dalam memprediksi sifat kompresibilitas tanah gambut dalam jangka waktu lama. Kata Kunci : gambut,
I"
kuctt geser, siJat kompresibilitcts, pengukurctn tekanan
INTRODUCTION
Peat is considered as problematic soils due
to low strength
characteristics.
large
defbrmation, high compressibility, and high magnitude and rates of creep. Moreover, there is some difficulty in accessing the sites witlr peat deposit because water table can be at. near or even above ground surface. fhe poor characleristics catrse constructiorr on peat subjected to problems of instability
pori
such as local sinking and developnrent of slip failure as r,vell as vet.v lar_ee printary and lcrnr term settlement under an e\,en ntoderate increase in load. In addition. bearing capacirr, is affected b1.' the higir uarer rable and the presenile of noodr debris in the soil. The soft water logged soil and peat takes a long tirre ro settle \\hen loaded due tcr erlbankntent or soil flll. Ur der this condirion. tlre ernbankntent \\ ill
r09
ii
A
I
7'h
A
nnual Scientific lvleeling
Jakarta, l3-11 November 2013
settle continually into the ground below' even if the soils do not fail by displacementThis paper presents the results of the study on engineering characteristics of peat in terms of the shear strength and long term compressibi I ity behavior.
2. METHODOLOGY Undisturbed samples for this study were obtained by block sampling method. The samples were retrieved from a shallow depth by digging up the soil to a depth of I nr and then a tube of 200 mm diameter and height of 200 mm was pushed into the soil and the soil was cllt at the base. The quality of samples was maintained by ensuring the sharpness of the tube and knife used to cr-rt the sample'
Field vane test was performed for assessment ofthe peat.
of in-situ undrained shear
the
strength
Physical and chemical properties such as natural moisture content, specific gravity, initial void ratio. unit weight, and acidity were
determined to
establish the
basic
characteristics of the soil. The soil was classified based on von Post degree of
humification, frber content. orgaltic content, and ash content. All tests were performed in accordance with the British (BS) ar''d U.S. (AS-l-M ) Standards.
Twelve sets of shear strength
test
containing three soil samples were tested using Direct shear apparatus. The samples are 60
mm diameter and 20 mm high- Each set contains three samples was subiected to normal load of 8 kPa, 16 kPa and 32 kPa respectively. The test was performed according to BS 1317 Part 7: Shear strength tests (total stress).
Large strain consolidation tests were performed using Rowe consolidation cell (Figure 2) with internal diameter of 151-4 mm and height of 50 mm. Each sample was sLrbjected to large strain consolidation pressures of 25, 50, 100, and 200 kPa or load increment ratios (LIR) of one. Drainage was :llor.red at the top and bottom plates, while ;\rrre-\\ ater pressure was measured at the .r-|iir ol the base. The tests were perfonned ,,,, -:ding to the procedltre suggested by Head -ri-
r
The time-compression and excess pore water pressure curves derived from Rowe consolidation test were analyzed using method proposed by Robinson (2003) in order to
develop the
compression-degree of
consolidation curve to identify the beginning of secondary consolidation (40). The primary consolidation and secondary compression were separated in order to assess the coefficient of consolidation (c,') and secondary compression index ll? as proposed by Robinson (2003)Besides the time-compression curve, a graph relating the void ratio at the end of each loading stage with the eflective pressure on logarithmic scale (e-log p') was plotted for a complete set of consolidation test data. In this case, the curve was plotted for prirnary consolidation only whereby the void ratio is corrected by eliminating the creep occurred after the completion of primary consolidation' The curve was used to obtain compression index, cc and pre-consolidation pressure (d")' The effect of initial compression was rninimized during the preparation of the test specimen and the consolidation test by Rowe cel l.
3. RESULTS AND DISCUSSION
3.1.
Peat Classification
Visual identification indicates that the peat
is dark brown, very soft, and laboratory
test of amount large a peat contains the shows that 4427, ASTM frber (90%). Thus, according to the peat is classified as flbrous with degree of decomposition (von Post scale) Ha. The texture is coarse which results in high initial permeability. The peat is acidic with pl-l :3.2The natural water content is 608 o/o lvhile the initial void ratio is 9 which yields in high compression index. Specific gravity is 1.47 which is very low.
3.2.
Shear Strength of Peat
Shear strength is considered as one of the most important parameters in engineering design and decision when dealing with soil as foundation material. Peat usLrally has very low shear strength and the deternrination of shear strength is difficult due to some factors such as
l7'h
Anntnl Scientifc Meeting
Jakarta, I 3-l
the origin of the soil, moisture content, organic matters and also on the degree of hun-rification. During the sampling stage, the sample
disturbance will also affect the evaluation of shear strength of peat. In general, shallow peat is more likely to have greater strength than more humified peat at depth (Culloch, 2006). Mostly, peat is considered as fiictional or non-cohesive material due to the fiber content and the spatial orientation of the fibers. However, the high friction angle of peat will not actually reflect high shear strength due to the fact that the flbers ane not always solid and may be filled with water and gas. The presence of fibers will modify the strength behavior of peat since the fibers can be considered as reinforcement and the fibers can provide effective stress where there is none and it induces anisotropy.
The determination of undrained slrear of peat is important because of the lrresence of peat is always below the strength
groundwater level. Thr.rs, in-situ test such as field vane shear and cone penetration test are very useful to evaluate the shear strength of peat. The undrained shear strength of peat (c,,) obrtained from field vane shear test on the peat used in this study is l0 kPa with sensitivity of 9. The high sensitivity value slrows a tendency o1'decreasing shear strength upon remolding. Sampling of peat is very difficult due to the nature of peat, thus laboratory testing can only give indicative results (Culloch, 2006). The most common laboratory test is usually aimed at determining the drain shear strength by direct shear test. Result obtained from the direct shear test on twelve sets of sample is shown in Figure l. The mean values indicate the average cohesion is 6-4 kPa while the internal friction is 22o ]l \{ru'\'-O4O16r-6,r
:
E.
3.3. Long Term Compression
I
November 201 3
Behavior
In general, the compressibility of a soil consists of three stages, namely initial compression, primary consolidation, and secondary compression. While initial compression occurs instantaneously after the application of load, the prir-nary consolidation and secondary compression are time dependent. The initial compression is due to the compression of small pockets of gas within the pore spaces and the elastic contpression of soil grains. The one-dimensional theory of consolidation developed by Terzaghi in 1925 carries an assuntption that primary consolidation is due to dissipation ol excess pore water pressure caused by an increase in
effective stress whereas secondary compression takes place under a constant effective stress at a slower rate after the
completion of the primary consolidation. Thus time-compression curve derived from consolidation test follows the fype I (.,S,') cllrve as shown in Figure 2.
the
'"''1 1..,t:,!r....,.,
t;ju,,,",
"
Figure 2: Types of Compression \-ersus Logarithmic of Time Cun e Derir ed liom Consolidation Test (Leonards .{nd Girault.
196
I
)
The compression behar it-rr of pear is different from that ol clar soil. It .',ccurs in
'i* -. -' il
:tl: o
t0 tt l0 \oltnai stress iqJ
,{o
Figure 1. Results of Direct Shear Test
three stases: printan consolidation. .econdan. and terlian' compressirrn. The secrrndan' compression occurs due not rrnlr to the compre>sir-rn trl paniu-les. but also rhe plastic f ielding of solid ntarerial t Sanrson and La Rochell:. l9-l r. Sr,rti r.searr'hers including
ill
I 7'h Annual Scientifc Meet ing Jakarta. I3-l4 November 20I3
Fox and Edil (1994) argued that the tertiary compression can be neglected because it generally started after the design life of structures.
The time-compression curves derived from results of one-dimensional consolidation test on peat usually resemble the Type 2 curve (Figure 2) in which the primary consolidation is very rapid and secondary compression does not vary linearly with logarithmic of time. Therefore the qr-rantification of secondary compression based on conventional compression-logarithmic of time method proposed by Cassagrande (1936) which was later extended by Dhowian and Edil (1980) fiequently under-estimates the settlement. In some cases, the time compression curve peat of follows Type 3 curve (Figure 2) where no inflection point was identified, thus tlre end
of primary consolidation (tp) cannot
be
predicted by Cassagrande method. Robinson (1999) pointed out that the end of primary consolidation is actually the tirne
pressure curves was proposed by Robinson (2003). If the primary consolidation and secondary compression were separated in the timecompression curve, the e-log p' curve can be constructed for primary consolidation only (Fox, 2003). The curve is required for the determination of compression index (c") and pre-consolidation pressure (cr'") of the soil. The typical time-compression curve obtained from consolidation test on soil used in this study is shown in Figure 3. The shape of the compression curve resembles the Type 2
curve (Figure 2) which is typical of compression of peat soil. The shape of the time-compression curve indicates that the deformation process of the peat deviates from
the simple model used ir-r Terzaghi's consolidation equation, which is the basis for the Cassagrande and Taylor's evaluations of primary consolidation and the estimation of the coefficient of consolidation.
when full dissipation of excess pore water pressure is achieved; thus, measurentent of
excess pore water pressure
-a/!-
durin-e
,i; in: bl
corrsolidation test is required. His observation
showed that the excess pore water pressure dissipation is completed earlier than tlre tinre
t._Ad: -
predicted from the inflection point of the settlement curve. Further anall sis by Robinson (2003) supported the argunrent made by previous researchers that the secondary compression of some soils actuallv stafis
Alog/
{r. i/
/
tJ: r a !tirr
I
r ,l*.rr",r*,_1,"n*.r,
r{ir
ri'.,
during the dissipation of excess pore water
3 Typical Time Compression Curve
pressure from the soil.
Figure
Terzaghi's one dimensional consolidation theory stated that the compression during primary consolidation is linearlr correlated with the dissipation of excess pore water pressure. Conversely, the actual cun e derived from laboratory consolidation test on peat soil was not actually follows a straight line because the settlement was actually due to the combination of excess pore water pressure dissipation on primary consolidation and creep or secondary compression. A method for separating the primary consolidation and secondary compression that occur- during the
Consolidation Test
compression, even though less significant than the primary consolidation in term of magnitude, could be very important in term of the design life of a structure. The secondary compression may have started during the process of excess pore water
consolidation process based
pressure dissipation.
on
timecompression and the time-excess pore water
112
from
The curve indicates that the primary is dominant in term of
consolidation
magnitude and the rate is high. The secondary compression occurred at a slower rate and is non-linear with logarithmic of time. This part
of the
Method suggested by Robinson is used in evaluating the time compression curve in Figure 3. The procedure is as follows:
I 7'h Annual Scientific Meeting Jakarta, I3-ll November 201 3
L
]
l.
Plot the compression versus log time (in minutes)
Plot the degree of consolidation U
o%
vs
log time, the time where at U reach 100Yo is the end of primary
i
Figure 4 shows that the compression index (cc) for primary consolidation is 3.15 which slightly lower than the slope evaluated based on total settlement i.e 5.0.
consolidation (ttoo) -1. Plot the compression versus degree of
-l
consolidation.
J. Draw a curve
and a straight line through
the points. The point where the curve deviates from linearity is identified as degree of consolidation where secondary compression begin (Uo) --i. Separate the primary consolidation curve from the secondary compression 6. Evaluate cu and c. based on primary consolidation curve only (Figure 4) 7. Evaluate 3o based on secondary compression curve which stafi at tp (Here the secondary compression curve is drawn on linear or log scale in both AXES.
The results of the analysis of
tirne compression curve are presented in Table l. The results indicate that cv decreases with increasing consolidation pressllre. This finding is in agreernent with the theory of consolidation, which stated that the coefficient cf rate of consolidation decreases with increasing consolidation pressure (Leonards and Girault, 1961). As shown in Figure 3, the secondary compression index co is not constant. However, the curve can be linearized by plotting both d" and time in linear scale as suggested by Robinson (2003). The linear lbrm enables the determination of m value which increases with increasing consolidation pressure.
l. Compression Characteristics Obtained from Robinson Procedure Table
p'
ttoo
tp
27.67 25.83 23.50 23.00
G't"^ 19.83 61.67 5.689 t7 .67 65.00 4.947 I 5.83 69.00 4.179 I 4.33 70.50 3.259
U
w' t^' ,^t", ca 25 !0 100 204
cr
nt : 0.0109
0.0124 0.0 t 57 0.021 I
o,".Jul3,*ru, looo Figure 4: Typical e-Log p, Curve for Determ ination of Compression Index
4. CONCLUSIONS The peat used in this study is of fibrous type. The undrained shear strength obtained from field vane test is l0 kpa, while drained shear strength measured by direct shear test is c: 6.4 kPa and d':22o.It should be noted that the high internal friction angle was derived from fiber content and not reliable. Evaluation of time settlement curve by Robinson (2003) method indicates that the secondary compression started as early as 65 Yo degree of consolidation. The beginning of secondary compression (to) is l8 minutes while the completion of primary consolidation (t1ss) is 26 minutes. The primary compression parameters c, : 3.5 while the coefficient of rate of consolidation (c,,) obtained ranges from 5.69 to 3.26 for a range of pressure from 25 to 200 kPa. The secondary compression index zir increases from 0.0102 to 0.0304 for consolidation pressure of 25 to 200 kpa. Consolidation test with pore water pressure measurement is very useful for the evaluation of compression behavior of peat. The
separation
of primary and
secondan.
consolidations is very impoftant for the evaluation of long term contpressibilitl, behavior of peat because the conventional evaluation of settlement based on the timecompression curve ma), result in o\ erprediction of prirnary consolidation and underprediction of secondan consolidation.
ll3
I 7'h Annual Scientifc Meeting Jakarta, l3-14 November 2013
REFERENCES Annual Book of ASTM Standards vol. 04.08 and 04.09. 1994.
British Standards Institution.l 981 . Methods of Test for Soils for Civil Eng. Purposes. London, BS 1377Culloch FM. 2006. Guidelines for the Risk Management of Peat Slips on the Construction of Low Volume/ Low Cost Road Over Peat. Scotland: For. Civ. Eng. For. Comm.. pp. l-46. Fox, P. J., Edil, T. B. and Lan, L. T. 1992. colc" Concept applied to Compression of Peat. Joumal of Geotech Eng, ASCE, I l 8(8): 1256-1263. Fox, P. J.2003, Consolidation and Settlement AnalysisThe Civil Eng. Handbook 2 Chen, W.F. and Liew, J.Y.R. Eds. Washington, D.C.
Gofar N and Sutejo, Y. 2007. Long
Term
Compressibility of Fibrous Peat. Malaysian Journal of Civil Engineering. 19 t2) 101-116. Holtz, R. D. and Kovacs, W. D. (1981) An Introduction to Geotechnical Engineering. Prentice-Hall, Inc., Englewood Cliffs, New Jersey. Head, K. H. 1982. Manual of Soil Laboratory Testing,
Vol 2:
Permeability, Shear Strength
and
Cornpressibility Tests. London: Pentech Press Ltd. Huat, B. B. K. 2004. Organic and Peat Soil Engineering.
Universiti Putra Malaysia Press. Leonards, G. A. and Girault, P. (1961).
A Study of
the
One-dimensional Consolidation Test. Proceedings 9th ICSMFE, Paris,
1
:1
16-130.
Macfarlane, I. C. 1969. Engineering Characteristics of Peat. Muskeg Eng HB, Ottawa, Canada, 3-30.
Robinson,
R. G.
1997. Determination
of
Radial
Coefficient of Consolidation by the Inflection Point Method, Geotechnique , 47 (5): 1 079- I 08 I .
Robinson, R. G. 1999. Consolidation Analysis with Pore Pressure Measurements. Geotechnique, 49(1): 127-t32. Robinson, R. G. 2003. A Study on the Beginning of Secondary Compression of Soils. Journal of Testing and Evaluation, 31(5):
l-l
0.
L. and La Rochelle, P.
19'72. Design and Performance of an Expressway Constructed Over Peat by Preloading. Canadian Geotechnical Journal,
Samson,
9:447-466.
t1+
