Showing papers on "Standard penetration test published in 2004"

Standard penetration test-based probabilistic and deterministic assessment of seismic soil liquefaction potential

Abstract: This paper presents new correlations for assessment of the likelihood of initiation (or “triggering”) of soil liquefaction. These new correlations eliminate several sources of bias intrinsic to previous, similar correlations, and provide greatly reduced overall uncertainty and variance. Key elements in the development of these new correlations are (1) accumulation of a significantly expanded database of field performance case histories; (2) use of improved knowledge and understanding of factors affecting interpretation of standard penetration test data; (3) incorporation of improved understanding of factors affecting site-specific earthquake ground motions (including directivity effects, site-specific response, etc.); (4) use of improved methods for assessment of in situ cyclic shear stress ratio; (5) screening of field data case histories on a quality/uncertainty basis; and (6) use of high-order probabilistic tools (Bayesian updating). The resulting relationships not only provide greatly reduced uncertai...

Estimating liquefaction-induced lateral displacements using the standard penetration test or cone penetration test

Abstract: A semiempirical approach to estimate liquefaction-induced lateral displacements using standard penetration test (SPT) or cone penetration test (CPT) data is presented. The approach combines available SPT- and CPT-based methods to evaluate liquefaction potential with laboratory test results for clean sands to estimate the potential maximum cyclic shear strains for saturated sandy soils under seismic loading. A lateral displacement index is then introduced, which is obtained by integrating the maximum cyclic shear strains with depth. Empirical correlations from case history data are proposed between actual lateral displacement, the lateral displacement index, and geometric parameters characterizing ground geometry for gently sloping ground without a free face, level ground with a free face, and gently sloping ground with a free face. The proposed approach can be applied to obtain preliminary estimates of the magnitude of lateral displacements associated with a liquefaction-induced lateral spread.

Drilled shaft design for sound barrier walls, signs, and signals

Abstract: The Colorado Department of Transportation (CDOT) uses drilled shafts to support the noise barrier walls and the large overhead signs and signals placed alongside the highways. These structures are subjected to predominantly lateral loads from wind. Current CDOT design for the drilled shafts is very conservative and lacks uniformity, which could lead to high construction costs for these shafts. CDOT commissioned a research study with the objective of identifying/developing uniform and improved design methods for these structures. Toward these goals, existing analysis methods for both capacity estimate and load-deflection predictions of drilled shafts supporting sound barrier walls, signs, and signals and typical soil and rock formations in Colorado are presented in a comprehensive manner. This includes the practice of CDOT engineers and consultants for design methods and geotechnical investigation, AASHTO design methods and specifications, and the design practice of the Ohio DOT. The accuracy of selected design methods for lateral and torsional responses of drilled shafts was evaluated by comparing predictions from these methods with measured "true" capacity and deflections from lateral and torsional load tests reported in the literature, performed in Ohio, and two new lateral load tests performed in this study as a part of the CDOT construction project along I-225 where noise barrier walls were constructed. A comprehensive geotechnical investigation program was also carried out at the two new lateral load test sites that included a pressuremeter test, Standard Penetration Test (SPT), laboratory triaxial CU tests, and direct shear tests. This allowed for evaluation of the accuracy of various testing methods employed for determining the soil parameters required in the lateral design methods. Finite element modeling has been developed and validated against the new load test data. Additional consideration of possible loading rate effect, cyclic loading effect, and ground water table fluctuations on the soil resistance are discussed. The appropriateness of the recommended factor of safety (FS) for the Broms method was further verified with LRFD calibration.

Unit Skin Friction from the Standard Penetration Test Supplemented with the Measurement of Torque

Abstract: The standard penetration test (SPT) supplemented with the measurement of torque (SPT-T) may be used to obtain a direct measurement of unit skin friction (fs) between the sampler and the surrounding...

Cavity and loose region of sandy ground evaluation method using specific resistivity

Abstract: PROBLEM TO BE SOLVED: To provide an evaluation method for a cavity and loose region of a sandy ground capable of appropriate determination by using the test results of the specific resistance distribution and the results of an original position test of a standard penetration test of the already confirmed EM exploration etc.; the cavity and loose region in the reclaimed land behind the quay are scarcely confirmed by boring tests at a plurality of sites only on points or on a line in the past. SOLUTION: The evaluation method of the cavity and loose region of the sandy ground is as follows: the specific resistance distribution of the objective ground is measured by the method such as the EM exploration, or the specific resistance tomography for grasping the relation between the relative density of the ground and the specific resistance; the original position test such as three component cone penetration test, or RI cone penetration test is performed; the relative density of the original position is converted from the result of the original position test; the correlation between the specific resistance of the specific resistance distribution and the original position relative density is determined; the relative density of the evaluation original point for evaluation as the cavity and the loose region 16 are determined where the range of specific resistance lower than that specifying the cavity and loose region 16 is used. COPYRIGHT: (C)2005,JPO&NCIPI

In Situ Test Protocols for Quality Assessments of Deep Mixing Columns

Abstract: Deep mixing (DM) technology involves the mixing of soils extending to large depths with cement, or lime, or other types of stabilizers for raising the strength of soft and compressible soils, reduction of settlements of roads, embankments, and enhancing the stability of excavation support and slopes. Quality Assurance (QA) of deep mixing methods used in the construction projects must be addressed to evaluate the effectiveness of DM treatment methods adapted in the field. If not addressed, columns with deficient strength and stiffness properties will induce damage to infrastructure built on them. Several in situ testing protocols for QA studies were developed as a part of a research study conducted for the National Deep Mixing Program. This protocol development was based on extensive literature reviews, documented case study information and surveys with practitioners associated with the in situ methods. This paper provides comprehensive details on three testing protocols of standard penetration test, cone penetration test and pressuremeter test. The protocols covered both step by step testing methodologies on soil columns, and interpretation methods for strength and stiffness properties. A case study example utilizing SPT protocol is presented to illustrate the steps in QA studies.

Artificial neural network model for prediction of seismic liquefaction of sand soil

Abstract: Based on simply analyzing the back propagation algorithm, the principles of the BP neural network are applied to predicting sand liquefaction with eight factors listed as follows: seismic intensity, epicenter distance, mean diameter, coefficient of non-uniformity, underground water depth, sand depth, blow number of standard penetration test, ratio of shearing stress. Through computing practical examples and assessing the model, the model is manifested to be scientific and effective with much more accurate results than the Norm method and seed simplified method. The results show that the method is an efficient one in solving nonlinear problems.

The application of surface wave test technique to estimating the bearing capacity of pile

Abstract: The method for determining the load bearing capacity of pile is summarized and the basic principle of the transient surface wave test technique is described in this paper. The application of this technique to estimating the bearing capacity of pile, in particular, is presented with a practical example. The standard penetration test blow count (N(63.5)) related to the shear wave velocity could be used to estimate the bearing capacity of pile. The correlation model of Vs with qsik and qpk was constructed through N(63.5). The transient surface wave could be used to test the shear wave velocity of soil around the pile and estimate the bearing capacity of pile.