108 research outputs found
Evaluation of Degree of Consolidation, Over Consolidation Ratio and Coefficient of Consolidation from CPTu tests in Alluvium Clays
No full textSoft soil was found in several areas in Indonesia, one of them is in Kalimantan Island, which the soft soil in the island mostly formed by Alluvium. One of the characteristics of the soft soil is that they are likely still in under consolidating stage. The usage of CPTu was found to be suitable to the soft soil as the device can record small numbers continuously and able to record pore water pressure. Key features in performing CPTu in under consolidating soft soil is the dissipation test. However, often the dissipation test ended before the 50% excess pore pressure dissipated, which causes commonly used method for interpretation unable to estimate u50. Inverse time (Whittle et. al., 2000; Lim et. al., 2014) and inverse square root time (Liu et. al., 2014) method was developed to overcame the limitation. Rahardjo et. al. (2016) also developed method for obtaining degree of consolidation (and OCR) using pore pressure ratio parameter (Bq) obtained from CPTu. Geotechnical investigation comprised advancing several cone penetration testings (CPTu) were carried out after failure occurred in a relatively flat area (RL +5m to +12m) after having built waste dump embankment to +70m elevation. Soft soil with 15m to 30m thickness was found beneath the embankment. This paper presents comparison of coefficient of consolidation using Teh & Houlsby (1991) method using parameters derived from inverse time and inverse square root time, also comparison for degree of consolidation and OCR in the Alluvium clays based on the dissipation data obtained from the testings. Result showed that the Alluvium clays in the upper 10m already over consolidated while between RL 0 to -20m are still under consolidating, with parameters obtained using inverse time and inverse square root time generally showing close value
Lesson learned from retaining wall failures: a geotechnical disaster
No full textThis article presents five failure cases of retaining wall which is obtained from literature and some personal documentation. One case is located in Singapore, two cases are located in Taiwan, and the other two cases are located in Indonesia. Among those five cases, four cases were the unloading problems and one case was the loading problems. The objective of this article is to summarize the causes of those failures, according to the literature study and to provide some recommendations to prevent similar events happened in the future. The failure of retaining wall is categorized as a geotechnical disaster because it is not only causing major economic losses but also some casualties also been reported. The main reason for the failure was the improper design of the retaining and supporting system. One of the good indication before failure would occur was excessive movements induced by excavation or fill. Hence, it was recommended to install a proper geotechnical instrumentation in the construction and the nearby area. Moreover, an excavation or fill project should be strictly operated and controlled by a safety management to avoid any casualties. The safety regulations should be supported and understood by all of the people involved in excavation or fill projects
Human centric object perception for service robots
No full textThe research interests and applicability of robotics have diversified and seen atremendous growth in recent years. There has been a shift from industrial robots operating in constrained settings to consumer robots working in dynamic environments associated closely with everyday human activities. Personal service robots to assist elderly, compliant robots with advanced perception skills for flexible manufacturing and autonomous driving vehicles for safe transportation are among the promising directions. In all these cases, robots have to work in close cooperation with human users and an intuitive higher level interaction between robots and layman users is essential for its widespread acceptability. Hence in this thesis, development of cognitive and perceptual skills in humans is studied and applied to the development of robot’s perceptual skills, especially based on visual information from a user interaction point of view.A physical robot is developed from scratch considering the aspects of affordability and user acceptability. A 9 DoF robot, LEA which incorporates a differential drive base, 4 DoF arm with a gripper and a pan-tilt neck supporting the robot’s head. The entire mechanics and control electronics are custom developed leading to decreased mechanical complexity and increased flexibility in physical dimensions. All the components are well integrated with a socially appealing industrial design which has been well received by the public and media. The limitations arising from simplified mechanics and affordable hardware are compensated by advanced adaptive vision algorithms to achieve the required functionalities of a service robot. A generic human centric architecture for highly autonomous and interactive robots is proposed to integrate various capabilities of a robot that are triggered by user interaction. A specific case of object recognition is investigated, as many tasks faced by such robots involve perception and manipulation of different household objects.An intuitive non-verbal interaction between a user and a robot for conveying objects of interest to the robot is developed. The developed spatial grounding model can detect the object of user interest independent of the relative position between the robot, the user and the object and without any prior training. This is achieved by a hybrid attention system combining bottom-up color saliency with depth image and top-down cues comprising user’s pointing direction and gaze. Robustness of gaze based attention system is improved by automatically switching between a keypoint based and a color based approach depending on objects’ texture.The recognition of these objects is achieved with a three layered semantic recognition framework that can incorporate multiple modalities of information. Developed based on studies of human perception, this method achieves recognition robustness in unconstrained domestic environments while providing semantic grounding with human users. Modalities of color, shape and object location have been incorporated into this recognition model while maintaining flexibility to include additional modalities. The first layer consists of semantic grounding modules that abstract raw sensory information into a probability distribution over meaningful semantic concepts familiar to humans. A second layer operates on these semantic features to obtain an object hypothesis based on every individual modality. The last layer performs knowledge association to estimate combined probability over known objects to obtain the final inference.A novel algorithm to track contours of objects and persons to allow exploration from different viewpoints is developed. Visual model of the target is refined by considering only the dominant 3D cluster within the initial bounding box. A tracking-by detection algorithm constrains the search space in the image by removing regions based on metric size constancy of the object and other structural patterns like perpendicular planes. A feature based on Color Naming System has been used with an online learning classifier to obtain a color probability map while the depth probability map is obtained by using a Gaussian model of the object’s depth distribution. An optimal fusion of different object modalities using a target-background dissimilarity measure is developed and is used in a graphcut framework to continuously obtain contours of the target object.The reliability of recognition of these objects in challenging domestic environments is enhanced using visual appearances from multiple views while incorporating the spatial relations between these viewpoints as well. A Sequence Alignment algorithm has been used with vector quantized features from each view to achieve view point correlation in object recognition. A fast Visual Odometry estimation has been used to obtain viewpoint relations in an unsupervised manner and this has been incorporated with segmentation to provide a standalone system that can be used in real world scenario. This system is made generic to be used with different feature vectors and a benchmark is created to compare the performance improvement achieved by the developed system with respect to single view object recognition using different feature vectors.Object recognition in service robots can be augmented by incorporating the context of objects’ use within the developed semantic recognition framework. The utility of an object can be understood by the actions performed by the user on the object and hence an Action Recognition system based on human skeletal tracking with a novelty detection method is developed to facilitate the incremental learning of new actions. Compact representations of skeletal structure are obtained using a Torso-PCA transform and are used as observations for a HMM based system to recognize user actions. Uncertainty in predictions, quantified as confidence measures are thresholded to detect unknown actions. These confidence measures are obtained through background models and different methods are evaluated with respect to sensitivity and specificity of recognition performance.Various algorithms are developed to enhance the reliability of object perception overcoming challenges posed by dynamic environments and affordable hardware by incorporating different modalities of information available to a robot. The development of algorithms in this direction is significant as these concepts can be readily extended to incorporate user and environment recognition to complete the perceptual capabilities of robots
EVALUASI FORMULA PENENTUAN DAYA DUKUNG AKSIAL TIANG PANCANG TUNGGAL MENGGUNAKAN DATA CPT BERDASARKAN METODE LANGSUNG (DIRECT METHOD)
No full textDewasa ini, perkembangan alat penyelidikan tanah di lapangan (in-situ testing) telah berkembang sangat pesat. Salah satu yang sangat populet dan luas digunakan dalam dunia geoteknik adalah alat Cone Penetration Test (CPT) atau yang lebih dikenal dengan istilah alat Sondir. Alat Sondir selain lazim digunakan untuk menentukan stratifikasi tanah, juga bisa digunakan untukmengestimasi daya dukung pondasi aksial tiang pancang tunggal. Salah satu alasannya adalah metode pengujian sondir sangat persis dengan mekanisme pemancangan tiang.Metode untuk mengestimasi daya dukung aksial pondasi tiang pancang menggunakan alat sondir adalah dengan menghubungkan skala atau algoritma dengan single-step process sehingga komponen daya dukung pondasi tiang (gesekan selimut dan daya dukung ujung tiang) dapatdikorelasikan dengan hasil bacaan (output) uji sondir secara langsung (direct method). Pada penelitian ini, sejumlah lima (5) uji kapasitas aksial tiang pancang (loading test : Kentledgemethod) digunakan untuk memverifikasi tujuh (7) metode langsung yang terpilih antara lain metode Begemann, Nottingham & Schmertman, Aoki & Velloso, Penpile, Price & Wardle, Meyerhoff, dan Philipponant.Dari hasil penelitian ini, didapatkan bahwa metode Nottingham & Schmertman merupakan metode yang baik dalam mengestimasi besarnya daya dukung aksial pondasi tiang pancang dengan besar simpangan kesalahan lebih kecil dari 10% dari acuan hasil loading-test
Development of Bearing Capacity Factor in Clay Soil with Normalized Undrained Shear Strength Behavior using The Finite Element Method
No full textAbstract. This paper presents a development of bearing capacity factor chart for strip footing laying on clay soil with normalized undrained shear strength using finite element method. Since stress history and normalized soil engineering properties concept were introduced in 1974 by Ladd and Foot, the new approach of design for clays has evolved. In order to accommodate this new approach, a study is conducted to see the effect of the normalized soil properties on bearing capacity factor, especially footings on clays. The results show that the effect of normalized undrained shear strength is more sensitive for soft clays rather than stiff clays. Abstrak. Makalah ini menyajikan pengembangan grafik faktor daya dukung untuk pondasi lajur pada tanah lempung dengan normalisasi kuat geser tak terdrainase tanah menggunakan metode elemen hingga. Sejak konsep historik tegangan dan normalisasi properti teknik tanah yang diperkenalkan pada tahun 1974 oleh Ladd dan Foot, pendekatan baru untuk perencanaan untuk tanah lempung telah berevolusi. Untuk mengakomodasi pendekatan baru ini, sebuah studi dilakukan untuk mempelajari efek dari normalisasi properti tanah pada faktor daya dukung, khususnya pondasi pada tanah lempung. Hasil studi menunjukkan bahwa efek normalisasi kuat geser tak terdrainase lebih sensitif terhadap lempung lunak dibandingkan lempung teguh
KAJIAN DAYA DUKUNG PONDASI MENERUS TERHADAP JARAK ANTAR PONDASI DAN KONDISI TANAH YANG BERLAPIS
No full textPenelitian ini dibagi menjadi dua bagian yaitu kajian daya dukung pondasi menerus terhadapjarak pondasi dan kajian daya dukung pondasi menerus terhadap profil pelapisan tanah yangberlapis. Berdasarkan teori yang berkembang saat ini, teori daya dukung pondasi dangkal tipemenerus yang mempertimbangkan jarak atau spasi antara pondasi dan tanah yang berlapis masihsedikit dilakukan. Sampai saat ini, terdapat beberapa rumus yang tersedia untuk mengakomodasidua kondisi diatas yang dikembangkan oleh Meyerhoff dan Stuart yang berdasarkan konsep LimitEquilibrium Method atau metode keseimbangan batas. Seiring dengan perkembangan jaman,metode-metode lain seperti metode elemen hingga banyak membantu dalam hal mencari solusidari permasalahan-permasalahan kompleks dalam bidang geoteknik. Oleh karena itu, tujuan daripenelitian ini adalah membandingkan rumus yang sudah ada (Limit Equilibrium Method) dengansolusi yang diberikan oleh metode elemen hingga. Dari hasil analisa yang diperoleh, untuk kajianjarak antar pondasi, ternyata apabila jarak antar pondasi semakin dekat, akan meningkatkan dayadukung tanah (tanah pasiran), sedangkan untuk pondasi yang terletak pada tanah lempungberlapis, maka perlu diperhatikan tebal lapisan pertama dan rasio kohesi antar lapisan karenaakan mempengaruhi daya dukung tanah
Evaluation of ASTM D 1143/D 1143M-07 and Chinese Code JGJ 106-2014 for Pile Load Testing using Finite Element Method
No full textPile foundation is a structural element utilized to transmit structural load into the soil mass. During design processes, many empirical equations used to estimate axial pile capacity, and a pile load test is conducted to validate the design. In Indonesia, it is common to adopt ASTM D 1143/D 1143M-07 for pile testing. Chinese Code JGJ 106-2014 is another viable option, which has gained popularity recently. This study investigated the load–settlement curves obtained using both codes. The analyses were simulated using the Mohr–Coulomb and the Hardening Soil models. The Hardening Soil model yielded more reasonable load–settlement and load–excess pore water pressure curves than the Mohr–Coulomb model. The reason due to the Mohr–Coulomb model unable to capture the non-linear behavior of soil properly. Furthermore, the results showed that ASTM D 1143/D 1143M-07 and JGJ 106-2014 yielded comparable results. Hence, both methods could be substituted each other
An assessment of Cikangkareng rockfall due to the Tasikmalaya earthquake on September 2, 2009
No full textThe earthquake that shook Tasikmalaya - West Java on Wednesday, September 2, 2009, amounting to 7.3 on the Richter scale at 02.55 pm was one of the geological natural disasters that affected Cikangkareng village - Cibinong District, Cianjur, West Java - Indonesia. According to the Bureau of Meteorology and Geophysics (BMG), Among 30 districts in Cianjur, 15 districts have great potential for land movement. The topographic condition is a fairly steep slope of hills with an almost upright angle ± 80 - 90·. In addition, a residential area was located at the foot of the hill. Thus, the geological conditions are fragile. Based on the map of land movement vulnerability (DVMBG, 2004), the Cianjur area is categorized as a zone of high movement potential of soil which means that movement of soil is easily triggered by rainfall and earthquakes. The Tasikmalaya earthquake event triggered a landslide on a large scale and caused rockfall. The material of the site collapse consists mainly of sedimentary rocks, sandstone rocks, sandstone, breccias, sandy tuffs, and yellow spots. The mineral testing results revealed that the existing minerals are Feldspar and Cristobalite. From the result of the slake-durability, the material has medium durability. The main cause is not only the acceleration in the horizontal or vertical direction of the rocks but also the seismic force can cause an increase in the water pressure in the pores and the rock fracture can give a change of pressure in the contact field of rock joint. As a result of this, the earthquake event triggered an avalanche on a large scale and caused rockfall. Due to the contact stress decreasing drastically, practically, the friction resistance of the joint plane could be significantly reduce
In-vitro cardiovascular flow measurements using particle image velocimetry: A patient specific validation study
No full textChemical Engineerin
Pengembangan Teori Tekanan Lateral Aktif pada Dinding Penahan Tanah Menggunakan Metode Elemen Hingga
No full textEstimating the value of lateral earth pressure acting on a rigid retaining wall is very important in the design of geotechnical structures. Various theories have been developed to calculate lateral earth pressure, each with it is own methodologies, equations, and assumptions. However, none of the studies above considered the lateral earth pressure equation based on the finite element method. In this study, conventional methods and finite element methods are used to determine the amount of active lateral earth pressure that occurs in the retaining wall, and a finite element method-based equation of active lateral earth pressure is proposed. Parametric experiments were also conducted to determine the active lateral earth pressure distribution's response to various parameters.Estimasi nilai suatu tekanan tanah lateral yang bekerja pada dinding penahan yang kaku sangat penting dalam desain bangunan struktur geoteknik. Berbagai teori telah dikembangkan untuk menghitung tekanan tanah lateral, dengan metode, persamaan dan asumsinya tersendiri. Namun, tidak satu pun dari penelitian di atas yang mempertimbangkan persamaan tekanan tanah lateral berdasarkan metode elemen hingga. Pada penelitian ini digunakan metode konvensional dan metode elemen hingga untuk mengetahui besaran tekanan tanah lateral aktif yang terjadi pada dinding penahan tanah, persamaan tekanan tanah lateral aktif berdasarkan metode elemen hingga diusulkan. Studi parametrik juga dilakukan untuk mengetahui respon distribusi tekanan tanah lateral aktif terhadap berbagai parameter. Dari hasil analisis yang telah dilakukan, ketika nilai sudut geser dalam bertambah, maka tekanan tanah lateral aktif yang bekerja pada dinding penahan tanah berkurang. Sebaliknya bila nilai berat isi tanah bertambah, maka aka tekanan tanah lateral aktif yang bekerja pada dinding penahan tanah bertambah
- …
