Liquefied strength ratio from liquefaction flow failure case histories

2002 ◽  
Vol 39 (3) ◽  
pp. 629-647 ◽  
Author(s):  
Scott M Olson ◽  
Timothy D Stark
Keyword(s):  
Shear Strength ◽  
Back Analysis ◽  
Penetration Resistance ◽  
Standard Penetration Test ◽  
Strength Ratio ◽  
Penetration Test ◽  
Case Histories ◽  
Tip Resistance ◽  
Flow Failure ◽  
Vertical Effective Stress

The shear strength of liquefied soil, su(LIQ), mobilized during a liquefaction flow failure is normalized with respect to the vertical effective stress (σ 'vo) prior to failure to evaluate the liquefied strength ratio, su(LIQ)/σ 'vo. Liquefied strength ratios mobilized during 33 cases of liquefaction flow failure are estimated using a procedure developed to directly back-analyze the liquefied strength ratio. In ten cases, sufficient data regarding the flow slide are available to incorporate the kinetics, i.e., momentum, of failure in the back-analysis. Using liquefied strength ratios back-calculated from case histories, relationships between liquefied strength ratio and normalized standard penetration test blowcount and cone penetration test tip resistance are proposed. These relationships indicate approximately linear correlations between liquefied strength ratio and penetration resistance up to values of qc1 and (N1)60 of 6.5 MPa and 12 blows/ft (i.e., blows/0.3 m), respectively.Key words: liquefaction, flow failure, liquefied shear strength, stability analysis, kinetics, penetration resistance.

Reconsideration of case histories for estimating undrained shear strength in sandy soils

1999 ◽  
Vol 36 (5) ◽  
pp. 907-933 ◽  
Author(s):  
C E (Fear) Wride ◽  
E C McRoberts ◽  
P K Robertson
Keyword(s):  
Shear Strength ◽  
Sandy Soils ◽  
Standard Penetration Test ◽  
Undrained Shear Strength ◽  
Soil Liquefaction ◽  
Penetration Test ◽  
Case Histories ◽  
Original Case ◽  
Undrained Strength ◽  
Undrained Shear

When sandy soils respond in a strain-softening manner to undrained loading, an estimation of the resulting undrained shear strength (Su) is required to determine the potential for flow liquefaction at a given site. One of the most commonly used methods for estimating the undrained strength of liquefied sand is an empirical standard penetration test (SPT) based chart (originally proposed by H.B. Seed), which was developed using a number of case histories. The original interpretations of these case histories are viewed by many workers and regulatory agencies as the most authoritative measure of the liquefied strength of sand. Consequently, in comparison, other less conservative methods are generally held in an unfavourable light. This paper reexamines the original database of case histories in view of some more recent concepts regarding soil liquefaction. The objectives of this paper are to explore and reassess the issues involved in the original assessment and to offer alternative views of the case records. The conclusions presented here indicate that alternative explanations of the liquefied strength of sand are not inconsistent with the original case histories. Key words: sandy soils, soil liquefaction, undrained strength, standard penetration test (SPT).

Use of laboratory data to confirm yield and liquefied strength ratio concepts

2003 ◽  
Vol 40 (6) ◽  
pp. 1164-1184 ◽  
Author(s):  
Scott M Olson ◽  
Timothy D Stark
Keyword(s):  
Shear Strength ◽  
Steady State ◽  
Yield Strength ◽  
Triaxial Compression ◽  
Sandy Soils ◽  
Friction Angle ◽  
Strength Ratio ◽  
Case Histories ◽  
Direct Simple Shear ◽  
Flow Failure

A laboratory database of triaxial compression test results was collected to examine the use of strength ratios for liquefaction analysis. Specifically, the database was used to: (i) validate the yield strength ratio concept (or yield friction angle); (ii) demonstrate the parallelism of the consolidation line and steady state line of many sandy soils; and (iii) validate the liquefied strength ratio concept. The yield strength ratio of contractive sandy soils in triaxial compression ranges from approximately 0.29 to 0.42 (corresponding to yield friction angles of 16°–23°), while the yield strength ratio from flow failure case histories (which correspond approximately to direct simple shear conditions) ranges from 0.23 to 0.31 (or yield friction angles of 13°–17°). As expected, the yield friction angle is greatest in triaxial compression, smaller in direct simple shear, and likely smallest in triaxial extension. The steady state line and consolidation line of many contractive sandy soils are parallel for a wide range effective stresses, steady state line slopes, fines contents, and grain sizes and shapes that are applicable to many civil engineering structures. As such, the liquefied strength ratio is a constant for many sandy soils deposited in a consistent manner. The liquefied strength ratio is inversely related to state parameter and ranges from approximately 0.02 to 0.22 in laboratory triaxial compression tests. Flow failure case histories fall near the middle of this range.Key words: liquefaction, liquefied shear strength, yield shear strength, collapse surface, steady state line, penetration resistance.

Liquefied Strength Ratio with Stress Densification and Low Stresses

2020 ◽  
Author(s):  
Timothy D Stark ◽  
Charles John MacRobert
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Sandy Soils ◽  
Penetration Resistance ◽  
Vertical Stress ◽  
Strength Ratio ◽  
Case Histories ◽  
Remedial Measure ◽  
Initial Penetration ◽  
Expected Increase

This paper presents a comparison of four (4) assumptions or approaches for using a liquefied shear strength ratio for sandy soils in cases where there has been a large increase in effective vertical stress, e.g., structure raising or remedial measure, that is outside the effective stresses of the case histories used to develop the empirical liquefied shear strength ratio and penetration resistance correlations. Changes in penetration resistance due to an increase in effective vertical stress are used in an example to illustrate the following four (4) assumptions for determining a liquefied shear strength ratio in such a post-liquefaction stability analysis: (1) initial effective vertical stress and initial penetration resistance, (2) initial effective vertical stress and the expected increase in penetration resistance due to the increase in effective vertical stress, (3) final effective vertical stress and initial penetration resistance, which is suggested, and (4) final effective vertical stress and final penetration resistance. This paper also presents suggestions for using a liquefied strength ratio at low effective vertical stresses, e.g., approaching the toe of a dam or embankment, in a post-liquefaction stability analysis.

A new genetic programming model for predicting settlement of shallow foundations

2007 ◽  
Vol 44 (12) ◽  
pp. 1462-1473 ◽  
Author(s):  
Mohammad Rezania ◽  
Akbar A. Javadi
Keyword(s):  
Genetic Programming ◽  
Programming Model ◽  
Standard Penetration Test ◽  
Shallow Foundations ◽  
Penetration Test ◽  
Case Histories ◽  
Contributing Factors ◽  
Artificial Neural Network Ann ◽  
Gp Model ◽  
Very High

In this paper, a new genetic programming (GP) approach for predicting settlement of shallow foundations is presented. The GP model is developed and verified using a large database of standard penetration test (SPT) based case histories that involve measured settlements of shallow foundations. The results of the developed GP model are compared with those of a number of commonly used traditional methods and artificial neural network (ANN) based models. It is shown that the GP model is able to learn, with a very high accuracy, the complex relationship between foundation settlement and its contributing factors, and render this knowledge in the form of a function. The attained function can be used to generalize the learning and apply it to predict settlement of foundations for new cases not used in the development of the model. The advantages of the proposed GP model over the conventional and ANN based models are highlighted.

scholarly journals GIS-based examination of peats and soils in Surfers Paradise, Australia

2014 ◽  
Vol 65 (1) ◽  
pp. 29-38 ◽  
Author(s):  
Haider Al-Ani ◽  
Erwin Oh ◽  
Gary Chai
Keyword(s):  
Shear Strength ◽  
High Water ◽  
Standard Penetration Test ◽  
Engineering Properties ◽  
High Water Content ◽  
Peat Layer ◽  
Penetration Test ◽  
Spatial Analyst ◽  
Zonation Maps ◽  
Low Shear

Abstract The subsoil conditions of Surfers Paradise in Southeast Queensland of Australia have been examined in terms of soil stiffness by using geographic information system (GIS). Peat is a highly organic and compressible material. Surfers Paradise (as a study area) has problematic peat layer due to its high water content, high compressibility, and low shear strength. This layer has various thicknesses at different locations ranging between R.L. . 10 to R.L. -19.6 m. Buildings in Surfers Paradise are using piled foundations to avoid the high compressibility and low shear strength peat layer. Spatial Analyst extension in the GIS ArcMap10 has been utilised to develop zonation maps for different depths in the study area. Each depth has been interpolated as a surface to create Standard Penetration Test SPT-N value GIS-based zonation maps for each depth. In addition, 8 interpolation techniques have been examined to evaluate which technique gives better representation for the Standard Penetration Test (SPT) data. Inverse Distance weighing (IDW) method in Spatial Analyst extension gives better representation for the utilised data with certain parameters. Two different cross sections have been performed in the core of the study area to determine the extent and the depth of the peat layer underneath already erected buildings. Physical and engineering properties of the Surfers Paradise peat have been obtained and showed that this peat falls within the category of tropical peat.

Cone penetration testing in stiff glacial soils using a downhole cone penetrometer

1992 ◽  
Vol 29 (3) ◽  
pp. 448-455
Author(s):  
Curtis R. Treen ◽  
Peter K. Robertson ◽  
David J. Woeller
Keyword(s):  
Penetration Resistance ◽  
Standard Penetration Test ◽  
Cone Penetrometer ◽  
Penetration Test ◽  
Cone Penetration ◽  
Penetration Testing ◽  
Cone Penetration Testing ◽  
Geotechnical Investigations ◽  
Drilling Rigs

Cone penetration testing (CPT) in Canada is usually performed using locally available drilling rigs. The limited pushing capacity of most drilling rigs coupled with the risk of damage to expensive cone penetrometers has tended to restrict the CPT to generally loose or soft soils. Therefore, in regions dominated by stiff glacial soils the more rugged standard penetration test (SPT) is still the most commonly used in situ test during geotechnical investigations. However, there are many limitations with the SPT with respect to interpretation and repeatability, especially the uncertainty with the energy delivered from various SPT hammer anvil systems. A downhole cone penetration test (DCPT) has been developed by modifying the equipment and procedure of the standard electric CPT. The DCPT consists of a simple, inexpensive electric cone penetrometer attached to a 1.5 m (5 ft) length of AW drill rod. The test is performed by pushing the cone 1.5 m into the base of an open borehole to produce a continuous profile of penetration resistance Qc, over the 1.5-m interval or whatever interval penetration is possible. The test incorporates the simplicity, ruggedness, and depth capability of the SPT but is able to define a near-continuous, accurate, and repeatable cone penetration resistance profile. The equipment and procedure of the DCPT is described in detail, and results from a near-continuous DCPT and an adjacent continuous CPT are presented and compared with the results obtained from an adjacent borehole with SPT. Excellent agreement was found between the results of the DCPT and the CPT. Key words : in situ, cone penetration testing, stiff soils.

Seismically induced settlement of ground experiencing undrained shaking and laterally constrained compression

2019 ◽  
Vol 56 (2) ◽  
pp. 155-172 ◽  
Author(s):  
Gholamreza Mesri ◽  
Marawan Shahien ◽  
Thierno Kane
Keyword(s):  
Factor Of Safety ◽  
Empirical Relationship ◽  
Penetration Resistance ◽  
Standard Penetration Test ◽  
Penetration Test ◽  
Shear Tests ◽  
Ground Shaking ◽  
Seismic Liquefaction ◽  
Direct Simple Shear ◽  
Settlement Analysis

A method is proposed for estimating seismically induced settlement of saturated sands experiencing undrained shaking and laterally constrained compression. An empirical relationship is developed between the seismic coefficient of vertical compression, mvs, and standard penetration test blow count, N60, as a function of factor of safety against liquefaction, Fℓ, based on data interpreted from 18 sets of laboratory cyclic direct simple shear tests and 23 cases of field observations of seismic liquefaction. The proposed method is compared with seismic settlement observed at 78 sites subjected to 7.1–8.0 magnitude earthquakes, and with predictions by the previous well-known methods of settlement analysis for undrained shaking. For silty–clayey sands, the significant effect of the plasticity of fines on seismic settlement is illustrated. The use of pre- or post-earthquake penetration resistance for back-analyses of field seismic settlement observations is examined. A tentative correction factor is suggested for seismic settlement estimated based on the assumption of undrained shaking and laterally constrained compression for liquefied saturated sublayers at small distances from drainage boundaries or under buildings with small breadths, which may experience volumetric compression during ground shaking.

Sign in / Sign up

Export Citation Format

Share Document