COMPARISON OF OVERCONSOLIDATED CLAY SETTLEMENTS CALCULATED BY ANALYTICAL 1D TERZAGHI CONSOLIDATION AND BIOT NUMERICAL ANALYSIS

ABSTRACT Consolidation is a phenomenon where air and water in the soil skeleton (i.e clay soil) are forced out due to loading. This condition can occur when clay soil is subjected to loading resulted from pressure in laboratory test, land fill or embankment, building and other structures in the field. Many studies have examined the consolidation of soil through numerical methods and One Dimensional Consolidation Theory of Terzaghi but rarely find a comparison between them. This study aims to find comparison of settlement due to consolidation based on the two methods. A simple simulation using different thicknesses of soil and different loading condition was carried out on saturated and homogenous overconsolidated soil. The settlement calculations were performed by analytical Terzaghi method and numerical analysis. The results obtained for the varied thickness of the soil samples show varied value of relative error which indicates that thickness is one of the factors contributing to the discrepancy of settlement between the methods. Variation of loading condition in each sample showed that the calculation results of two methods would be the quite similar if the loading is in the range of 40-52 kN/m2. Greater loading out of that range would cause the results of analytical analysis to be less than the numerical analysis

IZGLAĐENI MREŽNI SEIZMIČKI UČINAK PRIMIJENJEN ZA UPORABU ZEMLJIŠTA, STUDIJA SLUČAJA NA OTOKU KALIMANTAN, INDONEZIJA

Smoothed gridded seismicity is an analysis model in seismicity that allows for the obtaining of a rate based on the b-value and the same magnitude range. The data study has been collected and analyzed from a background source gathered by PusGen, referred to as the PusGen catalogue, with approximately 70 thousand data points. Two software programs (i.e. USGS PSHA and OpenQuake) were utilized in this study, and both programs have been proven as reliable in the creation of the 2017 Indonesia Earthquake Hazard Map. The final steps are to compare the acceleration map results with the Kalimantan Island land-use map and to analyze suitability development planning against potential hazards and earthquake risks. The results stated that: (1) acceleration due to the shallow background earthquake for the Kalimantan region, range from 0.00-0.25g (using USGS PSHA) and 0.0-0.4g (using OpenQuake); (2) meanwhile, based on the deep background earthquake source, the maximum accelerations that occur are 0.15g and 0.25g when using USGS PSHA and OpenQuake, respectively; (3) the utilized of land-use for the current and future years is in line with the results of the acceleration simulation. The study recommends to take into account the seismic aspects in new planning of the capital city, mining and residential areas in order to reduce the existing risks.Izglađeni (filtriran) mrežni seizmički učinak temelji se na analizi seizmičnosti, tj. izračunu vrijednosti b i odgovarajuće magnitude. U studiji su prikupljeni i analizirani podatci pozadinskoga izvora, prikupljeni u PusGen katalogu koji obuhvaća približno 70 000 podataka. Korištena su dva programska paketa koja su ranije pouzdano upotrijebljena kod izradbe karte potresnih rizika Indonezije 2017. godine, odnosno njihovi dijelovi nazvani USGS PSHA i OpenQuake. Završni dio računa bila je usporedba karte ubrzanja s kartom uporabe zemljišta na otoku Kalimantan te analiza daljnjega održivog razvoja s obzirom na opasnosti i rizik potresa. Dobiveni su sljedeći rezultati: (1) sila ubrzanja s obzirom plitke potrese u prostoru Kalimantana mijenja se 0 – 0,25 g (prema USGS PSHA), odnosno 0 – 0,4 g (OpenQuake); (2) temeljem dubokih seizmičkih izvora najveće ubrzanje izračunano je u intervalu 0,15 – 0,25 g (USGS PSHA, OpenQuake); (3) uporaba zemljišta, kako danas, tako i u budućnosti, treba pratiti rezultate simulacija (ubrzanja), za koje je preporučeno da postanu dio urbanoga planiranja glavnoga grada regije, ali i okolnih prostora u kojima se rudari

KERENTANAN LIKUIFAKSI WILAYAH KOTA BANDA ACEH BERDASARKAN METODE UJI PENETRASI KONUS

Pengetahuan mengenai kerentanan likuifaksi di suatu wilayah kota pesisir yang rawan gempabumi besar sangat diperlukan dalam perencanaan tataruang untuk mengurangi bencana seismik. Makalah ini menyajikan hasil evaluasi potensi likuifaksi di wilayah Kota Banda Aceh berdasarkan metode uji penetrasi konus untuk menghasilkan mikrozonasi kerentanan penurunan lapisan tanah akibat likuifaksi di wilayah ini. Hasil analisis menunjukkan bahwa potensi likuifaksi terdapat pada lapisan tanah pasir dan campuran pasir dan lanau, yang dicirikan oleh nilai tahanan konus dan hambatan setempat masing-masing lebih kecil dari 15 MPa dan 150 kPa pada kedalaman dan ketebalan yang bervariasi. Berdasarkan hasil perhitungan penurunan tanah, wilayah Banda Aceh dapat dibagi menjadi lima zona kerentanan. Zona kerentanan tinggi terutama terdapat di Kecamatan Kuta Alam dan Syah Kuala, sedangkan zona kerentanan rendah terutama terdapat di wilayah Kecamatan Banda Raya. Dengan demikian, investigasi geoteknik detil sangat diperlukan untuk mencegah kerusakan pada bangunan dan infrastruktur akibat likuifaksi di wilayah Kota Banda Aceh. Knowledge of liquefaction susceptibility is very important for spatial planning of a coastal city prone to big earthquakes. This paper presents the results of liquefaction potential evaluation based on cone penetration test to produce a microzonation map of liquefaction-induced ground settlement for Banda Aceh City. Results of the analysis show that liquefaction would occur in layers of loose to medium sand and silt-sand mixtures with the values of tip resistance and sleeve friction of less than 15 MPa and 150 kPa, respectively, at various depths. On the basis of ground settlement calculation, the city can generally be divided into five zones. High susceptible zone to ground settlement is mainly concentrated within the Kuta Alam and Syah Kuala Sub-District. Meanwhile, the zone of low susceptibility is within the Banda Raya Sub-District. Thus, detailed geotechnical investigation is necessary to mitigate liquefaction damage on buildings and infrastructures in Banda Aceh City

Microzonation of Soil Amplification Based on Microtremor, Spt and Cptu Data in Bandung Basin

Bandung Basin consists of Sunda-Tangkuban Perahu volcanic deposit that is made of lake sediment and an alluvial fan with fine to coarse-grained materials such as clay, silt and sand. The area is surrounded by several earthquake sources such as the Lembang, Cimandiri, and Baribis Faults. Therefore, it is important to understand soil dynamic problems with respect to seismic sources and soil properties. This research aims to investigate velocity amplification of the Bandung Basin using microtremor measurements and site classification based on the Standard Penetration Test (SPT) and Cone Penetrometer Test (CPTu). Velocity amplification was analyzed using the horizonal to vertical H/V spectral ratio, and site classification was determined using and  values. Microzonation maps were developed using Geographical Information System (GIS) to determine the correlation between soil velocity amplification and site class. The results revealed that velocity amplification levels in the Bandung Basin vary with a range of 1.3 to 26.5. Site classification ranges from very dense soil and hard rock (class C), stiff soil (class D) to soft clay soil (class E). Site class E dominates the southeast part of the Bandung Basin with a high value of soil amplification. This scientific information is critical for further spatial planning focusing on infrastructure and residential building. Cekungan Bandung berasal dari endapan vulkanik Sunda-Tangkuban Perahu yang terdiri dari sedimen danau dan kipas aluvial dengan material berbutir halus hingga kasar seperti lempung, lanau, dan pasir. Daerah ini juga dikelilingi oleh beberapa sumber gempa yakni sesar Lembang, Cimandiri, dan Baribis. Oleh karena itu masalah dinamika tanah yang dipengaruhi oleh sumber seismik dan sifat tanah perlu menjadi perhatian. Tujuan penelitian ini adalah untuk mengetahui amplifikasi kecepatan tanah di wilayah cekungan Bandung dengan menggunakan alat mikrotremor dan metode site classification berdasarkan uji SPT dan CPTu. Amplifikasi kecepatan dianalisis menggunakan perbandingan rasio spektral H/V dan site classification yang diperoleh dengan menggunakan nilai  dan . Peta mikrozonasi disusun menggunakan teknik Sistem Informasi Geografis (SIG) untuk menentukan korelasi amplifikasi tanah dan site class tanah. Hasil penelitian menunjukkan bahwa tingkat amplifikasi kecepatan di Cekungan Bandung bervariasi, berkisar 1,3 hingga 26,5. Site classification berkisar dari tanah yang sangat padat dan batuan keras (kelas C), tanah kaku (kelas D) hingga tanah lempung lunak (kelas E). Hasil penelitian menunjukkan site class E mendominasi bagian selatan Cekungan Bandung dengan nilai amplifikasi tanah yang tinggi. Informasi ilmiah ini diperlukan untuk perencanaan tata ruang kedepannya, dengan fokus pada infrastruktur dan bangunan tempat tinggal

MODELING OF SEPTIC TANKS SEEPAGE NEAR DUG WELLS IN MARGAHAYU VILLAGE, BANDUNG REGENCY

Dense settlements have an impact on pollution, one of which is domestic pollution which results in groundwater and soil water pollution at ground level. Identification of pollution that occurs below the soil surface (groundwater contamination) is more difficult to detect, so modeling is needed to find out how the rate of groundwater pollution rate. Modeling is done by using water sampling method at dug well at location adjacent to septic tank. Sampling ground water and infiltration modeling is done by using Geostudio SEEP/W software. The research area is in Margahayu village, Bandung regency. The results of laboratory analysis and physical observation in the field show that the Margahayu region has ammonium (NH4-N) content which is above the standard quality threshold. This condition is reinforced by modeling simulation results that there has been domestic sewage from septic tanks to dug wells. Pollution has reached groundwater level with depth ranged between 4-5 meters. The distance of wells adjacent to the septic tanks affects the quality of groundwater. In the KB area 17 it is indicated that the contamination in the residents' wells in harike-3i, KB new on the 32-40 day time frame, and KB new 2 on the 24th day. Distance sources of contaminants and soil permeability play an important role in determining the travel time of contaminants

Distribution of seismicity hazard levels using PGA analysis with the PSHA method in the Ciletuh Geopark Area, Sukabumi, Indonesia

The regional structure in Java Island, Indonesia, was influenced by the collisional activity of the Eurasian and Indo-Australian plates, which resulted from mélange rocks outcrops in Ciletuh. Ciletuh is one of the geotourism conservation areas included in the UGG (UNESCO Global Geoparks). This area is in the path of the Cimandiri Fault and the Sunda Strait Megathrust, resulting in a unique geological diversity and a place where the oldest rocks are exposed in West Java. In addition, the potential impact of seismicity on the Ciletuh geopark area is quite significant. The potential for seismicity can be analyzed and calculated. In this study, PGA (Peak Ground Acceleration) analysis on bedrock was conducted using the PSHA (Probabilistic Seismic Hazard Analysis) method. The data used for the PSHA method is in the form of background, fault, and megathrust provided by the National Earthquake Study Center (PuSGeN). This research shows that the PGA value in the Ciletuh Geopark area is influenced by how close it is to the location of the earthquake source. Pelabuhanratu Subdistrict has the highest PGA value based on all earthquake sources when combined

Rock slope stability monitoring system in the Batu Mountain area, Lembang, West Bandung

Gunung Batu is placed in Lembang, Langensari, West Bandung right of Lembang Fault line. Lembang Fault is an active fault with a slip rate between 1.95 – 3.45 mm/year and is expected to initiate an earthquake of Mw 6.5 – 7. Earthquakes in the Lembang Fault zone occurred in the 15th and 60th centuries BC, with an earthquake cycle every 170 – 670 years. From this, earthquake cycle estimates indicate that the Lembang Fault is in the final stage of the earthquake cycle. Gunung Batu is a populous area and has grown as a recreational area. Gunung Batu has a complex geological structure with potential rock slides. The observation and kinematic analysis results of the Gunung Batu area suggested that this area partly has an unstable slope and potentially has wedge and toppling failure. This condition of instability requires further monitoring to minimize damage and losses to populations around the Gunung Batu area. The development of slope stability monitoring tools has progressed significantly recently. Selecting the proper monitoring tool is the main component of data input to prevent possible hazards. The monitoring elements include rainfall, slope movement, and tilt movement. Sensor types that will be used in this monitoring system are integrated wireless monitoring systems. This system was developed to monitor the activity of the slopes of Gunung Batu, Lembang, West Bandung. The monitoring results for the last six months show the system is running well without errors

Tropical Volcanic Residual Soil

In West Lampung, Sumatra, Indonesia, tropical volcanic residual soils are formed from weathering of volcanic breccias in hydrothermal alteration areas with a thickness of up to 20 m. This soil has the characteristics of clayey silt, low to high plasticity, brownish-red color, has the potential to swelling, easily eroded, and slide when it is saturated, and contains the minerals kaolinite, halloysite, illite, dickite, nacrite, montmorillonite, despujolsite, hematite, and magnetite. The results showed that this soil can cause corrosion of steel and is widely used by the community as a medium for growing plants and vegetables and as a foundation for infrastructure (for example, houses). The volcanic residual soil of the research area had Low Rare Earth Element (LREE) potential and specific uses. The soil with characteristic low plasticity has Liquid Limit (LL) brine value 50%, was more ideal for the primary forest

Analysis of Bored Pile Behavior Using Numerical Simulation at Susukan Bridge Abutment (A1) Section II Stage I-1 Semarang � Ungaran, Semarang � Solo Highway

Semarang-Solo highway, which is located at Central Java Province, Indonesia, will connect between Semarang and Solo city. Problem that occurred during this project construction is large displacement take place north abutment Susukan Bridge due to characteristic of weathered clay shale. The objectives in this work are the study of numerical analysis through Plaxis Program which conducted to the bridge abutment, study of bored pile mechanical behavior due to soil movement and propose alternative design to protect the bridge abutment if abutment primary pile was not stable. All data that needed in this study were prepared and collected, for example data about soil properties, ground water elevation data, specification of pile and abutment cross section. Soil data was obtained from N-SPT data, unconfined compression direct shear test and other soil mechanical laboratory tests. Specification of pile was obtained from Pile Driving Analyzer (PDA) test and design drawing. Ground water elevation data was from report of bore log. Cross section of soil was obtained from geophysics and bore log. Validation step must firstly carried out before simulate others stage. Numerical analysis can be performed to obtain validation and simulate another construction stage in geotechnical problem. Validation was obtained from engineering judgement of soil properties. This study revealed that movement of tip and end of primary pile had tendention to toe direction except in cutting hill stage. In this stage, pile moved along 5,87 cm at the tip of pile in left direction from stage before. This condition can be happened as result of reducing loading on the slope. The biggest displacement occurred in pile was in operation and earthquake stage (approximately 6 cm in horizontal displacement incremental from operation stage). Stage with all construction installed without hill cutting was also performed in here to understand whether hill had significant impact to the abutment. This study shows us that hill had big influence to the stability of pile, thus horizontal displacement occurred in top of pile in this stage was approximately 77,9 cm. Analysis of pile structural nominal strength was also carried out and reveal that pile didn�t failure. Large displacement of Susukan Bridge abutment was not caused by failure of pile but by shear strength reduction of weathered clay shale

KOMPARATIVNA ANALIZA I EVALUACIJA FORMULE ZA PRETVORBU BROJA ODSKOKA SCHMIDTOVA ČEKIĆA U JEDNOOSNU TLAČNU ČVRSTOĆU – STUDIJA SLUČAJA: KOSINA ANDEZITNE STIJENE NA LOKACIJI GRAHA PUSPA, RASJED LEMBANG

The Unconfined Compressive Strength (UCS) test is one of the most common methods for determining the rock material strength value. However, the size and complexity of the instrument do not allow UCS testing to be carried out in the field. The UCS value can be estimated in the field by converting the rebound number using the Schmidt hammer test. This research aims to carry out a comparative analysis and evaluation of the conversion formula for rock compressive strength values resulting from the Schmidt hammer test and UCS test in a case study of andesite rock slopes at Graha Puspa, Lembang Fault, Bandung, Indonesia. Rock hardness testing was carried out using the Schmidt hammer test on five segments at Graha Puspa. UCS testing was carried out using a compressive strength machine on four samples in Graha Puspa. The test results show a rebound number value ranging from 31.67 - 45, while the UCS test results show a value range of 134.96 – 171.60 MPa. The results of the previously published empirical equations differed considerably from the results of the UCS tests on rock samples in the laboratory when estimating the UCS values. From this evaluation, this research proposed formulation development of andesite rock formulation in the Lembang Fault area. However, UCS testing on more samples is highly recommended in order to obtain a compressive strength conversion formula that is more suitable for the case study at this location.Ispitivanje jednoosne tlačne čvrstoće (UCS) jedna je od najtočnijih metoda za određivanje čvrstoće stijenskoga materijala. Međutim, veličina i složenost instrumenta za to ispitivanje ne dopuštaju provođenje takvih testiranja na terenu. Vrijednost UCS-a može se procijeniti na temelju broja odskoka Schmidtova čekića. Cilj je ovoga istraživanja provesti komparativnu analizu i evaluaciju formule za procjenu vrijednosti jednoosne tlačne čvrstoće stijene na temelju određivanja Schmidtove tvrdoće i samoga ispitivanja UCS-a u studiji slučaja za kosine andezitnih stijena na lokaciji Graha Puspa, rasjed Lembang, u blizini grada Bandung u Indoneziji. Ispitivanje tvrdoće stijene provedeno je Schmidtovim čekićem na pet uzoraka na lokaciji Graha Puspa. Ispitivanje jednoosne tlačne čvrstoće provedeno je u laboratoriju pomoću stroja za tlačnu čvrstoću na četirima uzorcima s lokacije Graha Puspa. Rezultati ispitivanja čvrstoće stijene pokazuju vrijednost broja odskoka u rasponu od 31,67 do 45, dok rezultati ispitivanja UCS-a pokazuju raspon vrijednosti od 134,96 do 171,6 MPa. Rezultati prije objavljenih empirijskih jednadžbi znatno su odstupali u procjeni vrijednosti UCS-a u usporedbi s rezultatima ispitivanja UCS-a na uzorcima stijene u laboratoriju. Na temelju ove evaluacije predložena je formula za procjenu čvrstoće andezitne stijene u području rasjeda Lembang. Međutim, preporučuju se daljnja istraživanja koja treba usmjeriti na veći broj testiranja UCS-a kako bi se dobila relevantnija formula za procjenu u studiji slučaja na ovoj lokaciji