scholarly journals KARAKTERISTIK ENDAPAN SEDIMEN PANTAI TERHADAP PENGARUH LIQUIFAKSI DI KAWASAN PESISIR PANGANDARAN DAN SEKITARNYA, KABUPATEN CIAMIS, JAWA BARAT

2016 ◽  
Vol 6 (3) ◽  
Author(s):  
Kris Budiono ◽  
Purnomo Raharjo
Keyword(s):  
Void Ratio ◽  
Ground Surface ◽  
Soil Mechanic ◽  
Geological Hazards ◽  
Survey Area ◽  
Ground Acceleration ◽  
Richter Scale ◽  
Simplified Procedure ◽  
Sand And Gravel ◽  
Critical Void

Liquifaksi adalah salah satu bencana geologi yang berhubungan dengan kegempaan, dimana tekanan pori dalam tanah atau sedimen mengalami peningkatan akibat getaran, sehingga mengakibatkan aliran air ke arah permukaan tanah. Liquifaksi umumnya terjadi pada dataran rendah termasuk kawasan pesisir. Daerah penelitian yang terletak di sekitar pantai Pangandaran dan Parigi terdiri dari endapan lempung, lanau, pasir dan kerikil yang bersifat lepas dan jenuh air, secara regional sering dipengaruhi oleh kekuatan gempa antara 5,5 – 6 skala Richter dengan percepatan tanah antara 150 – 200 mgal. Kondisi seperti ini apabila terjadi gempa sangat memungkinkan untuk terjadi liquifaksi. Berdasarkan hasil perhitungan secara kuantitatif nisbah pori kritis, tidak semua lokasi penelitian akan mengalami liquifaksi pada percepatan permukaan 150 – 200 mgal. Berdasarkan nilai tumbukan SPT yang dipakai untuk analisis “simplified procedure”, daerah penelitian secara umum relatif kecil terhadap bahaya liquifaksi. Namun demikian berdasarkan korelasi antara sifat mekanik tanah dengan nilai SPT, pada kedalaman 0 – 8 m terdapat lapisan sedimen yang cukup rentan terhadap liquifaksi. Kata kunci: Liquifaksi,sedimen pantai,Pangandaran Liquefaction is one of many geological hazards related to an earthquake, where the void ratio pressure in soil or sediment will increase due to the vibration, that causing water flow up to the ground surface. Generally liquefaction is occurred in the low lying areas including coastal zone. The survey area located in the Pangandaran and Parigi coasts, is consisted of clay, silt, sand and gravel, of loose and saturated properties, generally is frequently influenced by 5,5 – 6 Richter scale of earthquake strength with the ground acceleration between 150 – 200 mgal. The liquefaction will be occurred in this condition if there is an earthquake. Based on the quantitatively calculation of critical void ratio, the liquefaction at ground acceleration of 150 – 200 mgal will not be occurred at all of the survey area. Based on the number of blows of SPT which is used for simplified procedure analysis, it shows that the study area is less influenced by the liquefaction. Nevertheless , based on the correlation between soil mechanic properties and SPT value, there is potential liquefiable sediments layer between the depth of 0 – 8 meters. Key words: liquefaction, coastal sediment, Pangandaran

Predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio

2004 ◽  
Vol 41 (5) ◽  
pp. 787-795 ◽  
Author(s):  
Robert P Chapuis
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Saturated Hydraulic Conductivity ◽  
Effective Diameter ◽  
Predictive Capacity ◽  
K Value ◽  
Maximum Value ◽  
New Equation ◽  
Silty Soils ◽  
Sand And Gravel

This paper assesses methods to predict the saturated hydraulic conductivity, k, of clean sand and gravel. Currently, in engineering, the most widely used predictive methods are those of Hazen and the Naval Facilities Engineering Command (NAVFAC). This paper shows how the Hazen equation, which is valid only for loose packing when the porosity, n, is close to its maximum value, can be extended to any value of n the soil can take when its maximum value of n is known. The resulting extended Hazen equation is compared with the single equation that summarizes the NAVFAC chart. The predictive capacity of the two equations is assessed using published laboratory data for homogenized sand and gravel specimens, with an effective diameter d10 between 0.13 and 1.98 mm and a void ratio e between 0.4 and 1.5. A new equation is proposed, based on a best fit equation in a graph of the logarithm of measured k versus the logarithm of d102e3/(1 + e). The distribution curves of the differences “log(measured k) – log(predicted k)” have mean values of –0.07, –0.21, and 0.00 for the extended Hazen, NAVFAC, and new equations, respectively, with standard deviations of 0.23, 0.36, and 0.10, respectively. Using the values of d10 and e, the new equation predicts a k value usually between 0.5 and 2.0 times the measured k value for the considered data. It is shown that the predictive capacity of this new equation may be extended to natural nonplastic silty soils, but not to crushed soils or plastic silty soils. The paper discusses several factors affecting the inaccuracy of predictions and laboratory test results.Key words: permeability, sand, prediction, porosity, gradation curve.

Mantis shrimps Rissoides desmaresti in Tremadog Bay, North Wales

2001 ◽  
Vol 81 (4) ◽  
pp. 695-696 ◽  
Author(s):  
Kirsten Ramsay ◽  
Rohan H.F. Holt
Keyword(s):  
Average Length ◽  
Average Diameter ◽  
Survey Area ◽  
Horizontal Section ◽  
Mantis Shrimp ◽  
North Wales ◽  
Burrow Entrance ◽  
Sand And Gravel ◽  
Sandy Sediments ◽  
Burrow Morphology

In 1999 divers discovered a population of the burrowing mantis shrimp Rissoides (Meiosquilla) desmaresti (Crustacea: Stomatopoda) east of the St Tudwal's Islands, North Wales. This species has only sporadically been recorded in UK waters and commonly occurs in the Mediterranean. In summer 2000 the burrow morphology and distribution of these shrimps in the area east of the St Tudwal's Islands was investigated. Burrows were found at ten of the 15 sites investigated in a survey area measuring ∼18 km2. Burrow density varied from one to 11 burrows per 100 m2. The burrows were always recorded in sediments consisting of a mixture of mud, sand and gravel but were not present at sites with a high proportion of mud (>70%) or sandy sediments with very little mud ([les ]2%). Resin casts of six burrows revealed that these have a simple elongated U-shape, with an average length of ∼450 mm and depth of ∼160 mm. The average diameter of the burrow entrance was 19±2 mm and the diameter of the burrow along the horizontal section varied between 18 and 38 mm with a distinct constriction part way along.

Rain impact soil crust. IV. Packing of sand and silt fractions by raindrops

Soil Research ◽  
1991 ◽  
Vol 29 (2) ◽  
pp. 331 ◽  
Author(s):  
AJ Moss
Keyword(s):  
Void Ratio ◽  
Packed Bed ◽  
Stress Waves ◽  
Soil Crust ◽  
Structural Element ◽  
Loose Packing ◽  
Impact Events ◽  
Underlying Soil ◽  
Silt Layer ◽  
Critical Void

Comparison of resistance to fast and slow deformation by rain-packed and artificially prepared sand and silt fractions showed that, whereas sands are left in loosely packed states after accrual under rain impact, silts are left more densely packed, i.e. below critical void ratio. This contrast is attributed mainly to the declining importance of hydraulic penetration with pore size. Rain-packed silt is dilatant and cannot deform without expansion which, in turn, requires water entry at a rate compatible with the required deformation. In the short duration of rain-impact events, hydrodynamic time lagging occurs because water can move only slowly through the small silt pores. Consequently, densely packed silt remains essentially rigid. However, drop-outflow sheets are able to entrain silt and distribute it over the surface as densely packed bed-load deposits, thus maintaining its dilatancy. Sand, its larger pores invaded by hydraulic penetration jets which maintain loose packing, cannot behave in this manner. Relative stability of the silt layer on soil surfaces, and its suppression of hydraulic penetration, allow transmission of drop-generated stress waves which cause the immediately underlying soil to become compacted into the main structural element of the rain-impact soil crust.

Concept of critical void ratio used in estimating dynamic stability of sands

2009 ◽  
Vol 64 (2) ◽  
pp. 116-122
Author(s):  
E. S. Kushnareva ◽  
E. A. Voznesensky
Keyword(s):  
Dynamic Stability ◽  
Void Ratio ◽  
Critical Void

scholarly journals Study of Crater in the Gobi Desert Induced by Ground Explosion of Large Amounts of TNT Explosive up to 10 Tons

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Rongzheng Xu ◽  
Li Chen ◽  
Yuzhou Zheng ◽  
Zhan Li ◽  
Mingjin Cao ◽  
...  
Keyword(s):  
Conversion Coefficient ◽  
Near Field ◽  
Ground Surface ◽  
Failure Criteria ◽  
Gobi Desert ◽  
Large Weight ◽  
Fine Mesh ◽  
Contact Explosion ◽  
Protective Strategy ◽  
Sand And Gravel

Explosion craters on the ground surface induced by contact or near-field explosions have important implications, which can be used to assess blast consequences, guide the design of the explosion, or develop a protective strategy. In this study, to understand the crater characteristics induced by the contact explosion of large weight explosives, four field contact explosion tests were conducted on the surface of the Gobi Desert with large TNT charge weights of 1 ton, 3 tons, and 10 tons (test conducted twice). Cratering on the ground surface generated by large amounts of explosives was measured and evaluated, including the shape, depth, and diameter. A fine-mesh numerical model was developed and validated on the AUTODYN software platform, and a detailed parametric study was performed on the resulting craters. The effects of sand and gravel density, initiation method, shear modulus, and failure criteria were analyzed and discussed. An energy conversion coefficient was determined, and the corresponding theoretical equations were derived to predict the dimensions of the craters resulting from the large weight contact explosion. The calculated cratering characteristics were consistent with previous data and hence can be used in future engineering applications.

Challenges to modelling heave in expansive soils

2006 ◽  
Vol 43 (12) ◽  
pp. 1249-1272 ◽  
Author(s):  
Hung Q Vu ◽  
Delwyn G Fredlund
Keyword(s):  
Numerical Modelling ◽  
Volume Change ◽  
Void Ratio ◽  
Expansive Soils ◽  
Ground Surface ◽  
Expansive Soil ◽  
Coupled Analysis ◽  
Coupled Equations ◽  
Mathematical Equations ◽  
Unsaturated Expansive Soils

There are challenges associated with the numerical modelling of unsaturated expansive soils. The challenges are primarily related to the quantification of the void ratio constitutive surface, the characterization of the void ratio constitutive surface at low stresses and (or) suction, and the solution of coupled equations with several nonlinear unsaturated soil property functions. This study suggests that the void ratio constitutive surface of an expansive soil subject to a monotonic wetting path can be estimated from volume change indices obtained from conventional laboratory tests. The constitutive surfaces for both the soil structure and the water phase can be described using mathematical equations that allow net normal stress and suction to be reduced to zero. The solutions for two typical volume change problems are presented using both a coupled approach and an uncoupled approach. The first example problem simulates water leakage from a pipe under a flexible cover. The second example problem simulates the infiltration of water at ground surface. The results of the analyses are in accordance with anticipated behaviour. The results also show that the answers from an uncoupled analysis compared well with those from a coupled analysis. It is suggested that an uncoupled analysis may be adequate for most prediction of heave problems involving unsaturated expansive soils.Key words: heave prediction, numerical modelling, expansive soil, constitutive surface, uncoupled analysis, matric suction.

scholarly journals THE ACCELEROMETRIC NETWORK OF THE INDES-MUSA PROJECT IN THE KALOCHORI AREA: CONFIGURATION, DOCUMENTATION AND PRELIMINARY DATA INTERPRETATION

2017 ◽  
Vol 50 (2) ◽  
pp. 1100 ◽  
Author(s):  
E. Rovithis ◽  
K. Makra ◽  
A. Savvaidis ◽  
E. Kirtas
Keyword(s):  
Free Field ◽  
Ground Surface ◽  
Data Interpretation ◽  
Web Gis ◽  
Ground Subsidence ◽  
Northern Greece ◽  
Building Stock ◽  
Ground Acceleration ◽  
Preliminary Identification ◽  
Accelerometric Network

 A network of seven accelerometric stations on both ground surface and structures has been recently installed, as part of a multi-sensor network for monitoring seismic motion and ground subsidence in the broader area of Kalochori, west of Thessaloniki in Northern Greece, within the INDES-MUSA project. This network includes ground installations within the urban area, structural stations on top of structures and a freefield station away from the building stock. The documentation of stations is presented including shear wave velocity profiles of the subsoil at each location. A set of thirtynine earthquakes recorded so far by the accelerometric network is reported, followed by data processing procedures performed in the acquired waveforms. Comparisons of the processed earthquake recordings are presented referring to (a) the urbanground and the free-field stations in terms of peak ground acceleration, indicating amplification trends of ground motion, and (b) the structural and the nearby urban ground stations by means of top-to-base ratios in the frequency domain, towards a preliminary identification of the fundamental vibrational characteristics of the instrumented structures. The processed acceleration data are available through the INDES-MUSA Web-GIS portal.

Earthquake-induced Transient Ground Strains from Dense Seismic Networks

2008 ◽  
Vol 24 (2) ◽  
pp. 453-470 ◽  
Author(s):  
Roberto Paolucci ◽  
Chiara Smerzini
Keyword(s):  
Spatial Interpolation ◽  
Strain Tensor ◽  
Ground Surface ◽  
Numerical Differentiation ◽  
Engineering Practice ◽  
Ground Acceleration ◽  
Wave Passage ◽  
Seismic Networks ◽  
Relationship Of ◽  
The Relationship

Earthquake-induced transient ground strains are evaluated based on the records obtained by two dense seismic networks, namely the Parkway Valley, New Zealand, and the UPSAR, California, arrays. The calculations are based on the spatial interpolation of the recorded displacements and a numerical differentiation to obtain the strain tensor at ground surface. The computed peak ground strains show an important dependence on azimuth, by a factor of about two. Furthermore, the relationship of the peak ground strains as a function of the most common measures of ground motion severity, such as peak ground acceleration, velocity and displacement, is explored. Our results are in reasonable agreement with other published relationships and with some of the few available direct records of strain. However, they point out the limitations of the simplified evaluations used in the engineering practice, which uniquely consider the wave passage effect on the ground strain evaluation, and tend to significantly underestimate the observations.

Edgecombe earthquake

1987 ◽  
Vol 20 (3) ◽  
pp. 201-249 ◽  
Author(s):  
M. J. Pender ◽  
T. W. Robertson
Keyword(s):  
Structural Damage ◽  
Ground Surface ◽  
Strong Motion ◽  
Normal Fault ◽  
Lateral Spreading ◽  
Ground Acceleration ◽  
Paper Mills ◽  
North West ◽  
The North ◽  
The Town

On March 2 1987, at 01h 42m 34s UT an earthquake of magnitude (ML) 6.3 occurred near 37.91°S, 176.79°E close to the town of Edgecumbe in the North Island, New Zealand. The depth is provisionally estimated to be 12 ± 1 km. Seismic activity in the general area during the previous week culminated in a foreshock on March 2 of ML 5.2 at 01h 35m 37s. Four aftershocks with magnitudes in excess of 5.0 occurred on March 2 at 01h 51m 08s (ML 5.6), 02h 07m 23s (ML 5.1), 06h 56m 32s (ML 5.2) and 07h 55m 09s (ML 5.2). The earthquakes occurred at the end of summer after a long period of dry weather. Modified Mercalli Intensities of MM IX have been reported in and around Edgecumbe, with possible instances of MM X. Strong motion accelerographs recorded peak ground acceleration of up to 0.33 g within 15 km of the epicentre. The main shock produced a complex series of surface scarps, the longest being about 7 km long striking SW from Edgecumbe. About 1.3 m maximum extension occurred across the scarp with the area to the north-west being downthrown by about a maximum of 1.5 m which continued to subside slowly. Other smaller normal fault traces have also been detected as well as compressional rolls. There was extensive evidence of level ground liquefaction and lateral spreading near rivers. Both these phenomena produced eruption of sands at the ground surface. Some wells were observed to have increased flows or increased pressures whilst others were had decreased flows. General regional subsidence of the alluvial plains in the area up to 2m has been confirmed by levelling completed within three weeks of the earthquake. Structural damage was confined to the alluvial plains in which the town of Edgecumbe is centred. The depth of sediments on the plains is not less than 350 m. There was extensive minor damage to roads. Severe damage to many houses and other single storey structures. A dairy factory complex in Edgecumbe, two paper mills in Kawerau and a paperboard mill in Whakatane all sustained damage, in some cases considerable. At present information on the damage in the paper mills is not available.

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