Salah satu bentuk upaya mitigasi bencana alam adalah pemasangan peralatan untuk peringatan dini. Penelitian ini bertujuan untuk merancang sistem peringatan dini longsoran atau gerakan tanah. Untuk keperluan tersebut dirancang perangkatt elektronik berupa gabungan sensor getaran dan kandungan air tanah. Sensor getaran dibuat dari accelerometer komersial jenis MMA 7260 QT dengan sensitivitas maksimum 800 mV/g. Sensor kedua dirancang berdasarkan prinsip kapasitif yakni pengukuran luaran tegangan yang dihasilkan dari perubahan kandungan air pada suatu obyek. Model longsoran dibuat pada suatu box dari bahan mika, dan material tanah dibuat dari campuran kaolin dan pasir dengan kadar air bervariasi. Tanah dipadatkan dan membentuk lereng dengan kemiringan 75°, 65 , 60 dan 45. Box yang berisi tanah diletakkan di atas suatu vibrator dengan skala tertentu. Untuk merekam longsoran yang terjadi dipasang video camera. Hasil penelitian menunjukkan bahwa makin tinggi kemiringan suatu lapisan tanah (batuan), makin kecil skala getaran dan makin cepat pula waktu yang diperlukan untuk terjadinya longsoran dan sebaliknya. Kata kunci: tanah longsor, sistem sensor, getaran, kemiringan, kaolin dan pasir

The purpose of the present study is to estimate horizontal subgrade reaction coefficient (kh) of pilesfrom SPT N-value that is required to design piles against horizontal loading. This information is much demandedrecently due to the introduction of the limit state design of pile foundations where quantified uncertainty in the prediction of pile behavior is required. For this purpose 52 horizontal pile loading test results were collected from literatures and reports, which were compiled in a database. The actual number of test results put to the statistical analyses was 38 cases with pile top displacement and 21 cases with bending moment measurements along a pile. The statistical analyses were carried out in the two folds; First, the inverse analysis procedure was applied to each loading test result to obtain the coefficients in different soil layers. Then the obtained coefficient values were related to observed SPT N-values of the layers by the regression analysis. The pronounced feature of the regression analysis employed in this study is that it takes into account the magnitude of estimation uncertainty as well as the correlation structure of estimated kh for every pile automatically. The mean value of kh obtained from the recommended equation in this study gives very similar results to those of the major design equations used in Japan. The uncertainties associated with the recommended equation are presented, which are intended to be used in a reliability analysis of horizontally loadedpiles.

ABSTRACT

Recent year, reducing of open area and the extreme rainfall are reason for the flood in some city in Indonesia. The drainage and infiltrated well were constructed in some parts of the city could not solve the problem yet. The porous pavement can be applied to reduce run off, rate and pollutants. Reservoir base or sub base is an important layer as part of structure and also temporary store rainfall water before infiltrate to the subgrade. This study assessed characteristic and gradation some types of materials as stone crush, limestone and steel slag for porous pavement and evaluate this performance based on California Bearing Ratio (CBR) and porosity. Naturally these characteristics are contrary, in which for high porosity materials will have low bearing capacity. There are 7 gradations consist of 4 gradations in coarse aggregate and 3 gradations based on Bina Marga (Indonesian Highway Agency). The result showed that CBR of stone crush is high in uniform course material gradation than limestone and steel slag. In the term of porosity, the result completely the same for all materials in which the uniform gradation give the high porosity. It makes sign the influence of hardness and gradation of material will give contribution for bearing capacity and only gradation influence to porosity. The material are suitable for reservoir layer of porous pavement for light traffic load. Gradation band is lied between Bina Marga and NAPA and AASHTO specification.