Effect of Seismic Loading on Variation of Pore Water Pressure During Pile Pull-Out Tests in Sandy Soils

Experimental model was done for pile model of L / D = 25 installed into a laminar shear box contains different saturation soil densities (loose and dense sand) to evaluate the variation of pore water pressure before and after apply seismic loading. Two pore water pressure transducers placed at position near the middle and bottom of pile model to evaluate the pore water pressure during pullout tests. Seismic loading applied by uniaxial shaking table device, while the pullout tests were conducted through pullout device. The results of changing pore water pressure showed that the variation of pore water pressure near the bottom of pile is more than variation near the middle of pile in all tests. The variation of pore water pressure after apply seismic loading is more than the variation before apply seismic loading near the middle of pile and near the bottom of pile and in loose and dense sand. Variation of pore water pressure after apply seismic loading and uplift force is less than the variation after apply seismic loading in loose sand at middle and bottom of pile.

Approximate Calculation and Feature Analysis of Electric Field in Space by Thunderclouds

The calculation of electric field in space excited by thunderclouds is an important basis for lightning warning and protection. In numerical calculation of the electromagnetic field, it is often necessary to perform multiple loop nesting calculations on several triple integrals, which consume a lot of computing resources. In order to shorten the calculation time and improve the calculation efficiency, the electric field excited by the charged thunderclouds in space is theoretically derived with the analytical method by the thundercloud cylindrical charge pile model and based on the electrostatic field theory. The complex integrand function is approximated, so that the analytic expression of electric field in space is obtained in this paper. Through simulation and comparison, it is found that the approximate solution and the exact solution are similar in size, the change trend is the same, and the approximate analytical expression can be used for the approximate calculation of the electric field in a short range. Under certain conditions, the approximate solution can be converted into an accurate solution, which can be used for the accurate calculation of the electric field. Approximate calculation not only simplifies theoretical derivation but also improves calculation efficiency. The calculation time has been shortened from tens of hours to less than one second by using different calculation methods, which is a difference of 7 orders of magnitude. With approximate analytical expression, the electric field excited by charge pile with typical structures in thunderclouds in space is calculated and the characteristics of that are analyzed in this paper. For lightning protection of mobile targets, approximate calculation is of great significance in shortening the lightning warning time and enhancing the protection effect.

ANALISIS STABILITAS DAN DEFORMASI LERENG VILLA SEKEQ GRUPUK DENGAN SIMULASI NUMERIS

Perkembangan pariwisata di pulau Lombok semakin meningkat seiring dengan di kembangkan Kawasan Ekonomi Khusus (KEK) Mandalika, sehingga banyak dibangun tempat penginapan baik itu hotel maupun villa. Salah satu daerah wisata yang sedang berkembang disekitar KEK yaitu daerah Grupuk. Salah satu kasus gerakan massa tanah, yaitu bangunan Vila Sekeq yang berada di lereng perbukitan dengan kemiringan lereng berkisar antara 60° - 75° yang telah mengalami gejala geologi. Untuk mencegah potensi terjadinya longsoran di lereng Vila Sekeq, maka perlu dilakukan suatu analisis terhadap stabilitas dan deformasinya. Metode yang digunakan yaitu melakukan kajian data laboratorium dan data lapangan hasil bore log untuk mendapatkan karakteristik tanah dan batuan. Selanjutnya, data laboratorium dan data lapangan digunakan sebagai parameter input dalam simulasi numeris dengan Plaxis. Simulasi dilakukan dengan idealisasi 2D pada kondisi plane strain dan menggunakan model Mohr-Coulomb untuk tanah dasar. Dinding penahan bore pile yang memanjang dikaki lereng dengan materialnya di dekati model linear elastic. Simulasi numeris dilakukan dalam kondisi sebelum ada villa, kondisi lereng eksisting dan kondisi lereng setelah pemasangan bore pile. Model geometri dan perlapisan bawah permukaan berdasarkan stratigrafi perlapisan tanah hasil penyelidikan geoteknik yang terdiri dari lanau pasiran, pasir lanauan, lanau pasiran dan breksi gampingn. Simulasi numeris dengan Plaxis menunjukkan deformasi dari kondisi eksisting ke kondisi pemasangan bore pile mengalami peningkatan karena bore pile menambah beban pada lereng namun peningkatan deformasi tidak terlalu signifikan. Kondisi lereng sebelum ada villa tergolong stabil karena angka aman (SF) 1.3587, selanjutnya stabilitas lereng kondisi eksisting yang ditandai dengan angka aman (SF) 1.1878 sehingga lereng menjadi tidak stabil karena SF kurang dari 1.2. Untuk memperbesar angka aman supaya tidak terjadi longsoran, maka dilakukan pemasangan bore pile sedalam 12 meter, setelah pemasangan bore pile angka aman (SF) mengalami kenaikan menjadi 1.2154 sehingga lereng menjadi stabil (aman).

Experimental Study on Development of Mooring Simulator for Multi Floating Cranes

In this study, the coupled motion of a mooring system and multifloating cranes were analyzed. For the motion analysis, the combined equations of motions of the mooring line and multifloating cranes were introduced. The multibody equations for floating cranes were derived from the equations of motion. The finite element method (FEM) was used to derive equations to solve the stretchable catenary problem of the mooring line. To verify the function of mooring simulator, calculation results were compared with commercial mooring software. To validate the analysis results, we conducted an experimental test for offshore operation using two floating crane models scaled to 1:40. Two floating crane models and a pile model were established for operation of uprighting flare towers. During the model test, the motion of the floating cranes and tensions of the mooring lines were measured. Through the model test, the accuracy of the mooring analysis program developed in this study was verified. Therefore, if this mooring analysis program is used, it will be possible to perform a mooring analysis simulation at the same time as a maritime work simulation.

Tracking signal propagation through landscapes using a granular avalanching system

<p>Landscapes have the ability to transmit environmental signals or inhibit them. The mechanisms by which landscapes do this are largely unquantified, but is probably due to the ability of landscapes to transiently store and release sediment which acts as a medium for energy to propagate. Previous experiments using 1D avalanching rice piles suggest that stochastic collapses can overprint, or shred, periodic sedimentary signals (Jerolmack and Paola (2010), as measured using mass efflux from the experimental rice pile. Jerolmack and Paola (2010) defined a threshold for successful surface signal propagation: Tx, where signals with a period less than Tx are shredded, unless the magnitude of the signal is sufficiently large. We aim to utilise the rice pile to further investigate signal propagation across a landscape, and the thresholds for this, by quantifying inter-particle interactions and the mechanics of how signals propagate using a quasi-2D rice pile model, built using MFiX-DEM code. This open source, physics model utilises individual particles which compose the solid phase whilst treating the fluid as a continuum. The rice grains in the model are represented by spherical particles, where each individual particle, or cluster of particles, can be tracked through each time step using a coordinate axis system, allowing internal dynamics, such as avalanche sizes and sediment residence times, to be quantified. To certify the model replicates the self-organised nature of an experimental rice pile, sensitivity tests were performed by systematically changing two key parameters controlling grain interactions: the friction coefficient and the coefficient of restitution, alongside the sediment flux. To calibrate the results of the sensitivity analysis, mass efflux through time and the corresponding power spectra are compared to real experimental rice pile results and statistical rice pile models. It is hoped this work will provide fundamental insights into how a signal propagates through a landscapes, and how they are shredded in the process.   </p>