Dense Sand Deposits Research Articles

Response of a Dense Sand Deposit During 1993 Kushiro-Oki Earthquake

In the 1993 Kushiro-oki Earthquake of Richter magnitude 7.8, simultaneous recording of earthquake motions was successfully made at the ground surface and at a depth of 77 meters in a dense saturated sand deposit. The peak horizontal acceleration was 0.47 g on the ground surface and 0.21 g at a depth of 77 meters. The acceleration record at the ground surface showed a distinctive ground response, which consisted of a cyclic motion having a period of about 1.5 seconds overlain by a spike at each peak of the motion. In order to study the mechanism of this peculiar ground response, effective stress analysis was conducted on the dense saturated sand deposit. The model used for this study was a strain space multiple mechanism model, which takes into account the effect of principal stress axis rotation. The recorded earthquake motion at a depth of 77 meters was used as the input earthquake motion for the analysis. Sampling after in-situ freezing was done in order to evaluate the properties of the sand. The results of the analysis indicated that the observed ground response was due to the effect of dilatancy of sand, which plays a significant role in the response of the dense saturated sand deposits during strong earthquake motions.

Geology of Indianapolis, Indiana, United States of America

The engineering geology of Indianapolis, Indiana, is strongly influenced by glacial drift, which covers Marion County with a thickness varying from 10 to 350 ft (3.1 to 106.7 m), averaging 140 ft (42.7 m). Nearly all major structures are supported on spread footings bearing either on overconsolidated Wisconsin till or on dense sand and gravel outwash deposits along White River or Fall Creek. Spread footings supporting high rise buildings (up to 38 stories) in downtown Indianapolis are typically designed for bearing pressures of 8 to 12 kips/ft 2 (3.9 to 5.9 kg/cm 2 ). For the relatively small number of structures supported on deep foundations, pressure-injected footings, auger cast piles and drilled piers are the most common types. The main geologic resources of commercial importance in Marion County are sand and gravel, which are obtained from outwash deposits along major streams, and, to a lesser degree, mined limestone. Ninety-five percent of the water withdrawn by the Indianapolis Water Company is from surface sources, as three water supply reservoirs have been formed by constructing dams across major streams. Recent studies have shown that significant quantities of ground water are available within outwash aquifers along White River and Fall Creek.

Bearing capacity of foundations on a weak sand layer overlying a strong deposit

The ultimate bearing capacity of footings resting on subsoils consisting of a weak sand layer overlying a strong deposit has been investigated. Based on model tests of strip and circular footings in a loose or compact sand layer overlying a dense sand deposit, the classical equation of bearing capacity of footings on homogeneous sand was extended to cover cases of these footings in layered sands where the upper layer is the weaker. The theory compared well with the available model test results. Design charts are presented.

Liquefaction and Cyclic Mobility of Saturated Sands

The prediction of the behavior of saturated sands during eathquakes, in the last few years, has become an important concern in regard to foundations of nuclear power plants, especially for medium dense and dense sand deposits. An introductory section of this paper defines the basic phenomena that can be observed in a saturated sand when subjected to cyclic loading, i.e., liquefaction and cyclic mobility.

Analysis and Performance of a Braced Cut in Sand with Large Deformations

The paper is divided into two parts. The first part deals with the systematic program of measurements undertaken on an open braced cut in dense sand at the Greenway Pollution Control Centre in London, Ontario. In the second part, the experimental data are analyzed and a new solution is presented based on Dubrova's analysis, which related qualitatively and quantitatively the active earth pressure distribution to the mode of deformation of a retaining structure.The roughly L-shaped excavation measured 68 × 42 ft (20.7 × 12.8 m) for the longest leg, the other leg was 30 × 23 ft (9.1 × 7.0 m). The temporary bracing system consisted of interlocking steel sheet piles (Larssen IIIN), and wales and struts from wide-flanged steel sections. The maximum depth of the cut was 50 ft (15.2 m) below ground elevation of 722 ft (220.1 m). The soil consisted of fine uniform dense sand having a relative density varying from medium to very dense. The natural water level was approximately 20 ft (6.1 m) below the ground surface prior to construction.The instrumentation program was carried out during the 6-month construction period (January–June 1964) and consisted of measuring: (1) The strut loads with a mechanical strain indicator (Whitmore gauge) over 8 in. (20.3 cm) gauge lengths, (2) The deformation of the north wall in a horizontal and a vertical plane, (3) The water levels and water pressures from borehole and standpipe observations, and (4) The active and passive earth pressures over the cut with 'Geonor vibrating-wire pressure transducers mounted flush on two adjacent sheet piles of the north wall.Field and laboratory tests supplied the necessary soil data.Comprehensive measurements of this kind in deep cuts in sand, prior to this London investigation, had only been made in Berlin, Munich, and New York. But at London, for the first time the actual distribution of earth pressures in sand were measured on a full-scale braced wall.The analysis of the experimental data showed that the earth pressure distribution can be approximated by the extended Dubrova’s solution. The agreement between the total active earth pressure obtained from the pressure cells and the corresponding Coulomb values varied from excellent (upper bound) to good (lower bound).An experimental relationship between the horizontal soil strain and the variation of K-values over the depth of the cut was established.The different theories for predicting Ko-values do not seem to apply to over consolidated dense sand deposits. The experimental Ko-values, rather, agree with other published experimental values for similar soils.The strut load readings were somewhat erratic, not necessarily corresponding to the excavation progress. The total strut loads were lower than the corresponding forces from the earth pressure cells or the corresponding Coulomb values.