Field P–y curves in weathered rock

2007 ◽  
Vol 44 (7) ◽  
pp. 753-764 ◽  
Author(s):  
Kook Hwan Cho ◽  
Mohammed A Gabr ◽  
Shane Clark ◽  
Roy H Borden
Keyword(s):  
Field Tests ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Weak Rock ◽  
Strain Gages ◽  
Weathered Rock ◽  
Clay Model ◽  
Rock Model ◽  
Stiff Clay ◽  
Subgrade Modulus

In weathered and decomposed rock profiles, the lack of an acceptable analysis procedure for estimating lateral load–displacement response of drilled shafts is compounded by the unavailability of weathered material properties, including the material's lateral subgrade reaction modulus. Such deficiency often leads to the overdesign of the drilled shaft foundation. Six field tests were conducted on drilled shafts to investigate the shape and magnitude of P–y curves in weathered rock material at three locations in North Carolina. The tested shafts were instrumented using dial gages, strain gages, and continuous vertical inclinometers. The measured load versus deflection data are used to study the stiffness response of weathered rock. Measured lateral responses are compared with the results estimated based on a "weak rock" model and a stiff clay model. The comparison shows that Reese's weak rock model overestimated the resistances of the tested shafts while the stiff clay model consistently underestimated the measured shaft resistances. The measured and computed results are analyzed and discussed.Key words: drilled shaft, weathered rock P–y curve, subgrade modulus, ultimate resistances in weathered rock, verification tests.

Expansive concrete drilled shafts

1985 ◽  
Vol 12 (2) ◽  
pp. 382-395 ◽  
Author(s):  
Shamim A. Sheikh ◽  
Michael W. O'Neill ◽  
M. A. Mehrazarin
Keyword(s):  
Load Transfer ◽  
Stress Path ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Cement Concrete ◽  
Bored Pile ◽  
Expansive Concrete ◽  
Stiff Clay ◽  
Expansive Cement

A hypothesis is presented in this paper that states that expansive cement concrete produces a stronger bond between the concrete in a drilled shaft (bored pile) and the surrounding soil than does normal cement; this results in an increase in the frictional component of capacity and a reduction in the settlement of the shaft at working load levels.Four types of expansive cement, type "K" cement (the expansive cement available commercially) and three made from commercially available materials, were tested for their expansion characteristics; two of them were selected to be used in two instrumented drilled shafts in stiff clay. Normal (type 1) cement was used in a third shaft to serve as a reference. The three shafts were tested to failure after essentially all the expansion was deemed to have taken place in the two expansive concrete shafts. Lateral and longitudinal expansion of the shafts were monitored during the curing period. Load–settlement behaviour and load transfer between shafts and soil during the tests were studied.The test results permitted the preliminary conclusion that expansive cement concrete can increase the frictional capacity of drilled shafts in stiff clay by as much as 50% and reduce the settlement by about 50%. The results are valid for short-term behaviour of drilled shafts made of expansive cement. The long-term behaviour of such shafts remains to be studied. Key words: base bearing capacity, bored pile, cement (expansive), concrete (structural), drilled shaft, ettringite, expansion, frictional capacity, settlement, stress path.

scholarly journals Development of Rock Embedded Drilled Shaft Resistance Factors in Korea based on Field Tests

2019 ◽  
Vol 9 (11) ◽  
pp. 2201
Author(s):  
Seok Jung KIM ◽  
Sun Yong KWON ◽  
Jin Tae HAN ◽  
Mintaek YOO
Keyword(s):  
Design Method ◽  
Limit State ◽  
Field Tests ◽  
Load Test ◽  
Drilled Shaft ◽  
Displacement Curve ◽  
Base Resistance ◽  
Resistance Factors ◽  
Shaft Resistance ◽  
The Us

Load and resistance factor design (LRFD) is a limit state design method that has been applied worldwide. Because the data for determining LRFD factors in Korea has been insufficient, the resistance factors suggested by American Association of State Highway and Transportation Officials (AASHTO) in the US have been used for design in Korea; however, these resistance factors were defined based on the characteristics of the predominant bedrock types in the U.S. As such, it remains necessary to determine resistance factors that reflect the bedrock conditions in Korea. Accordingly, in this study, LRFD resistance factors were determined using 13 sets of drilled shaft load test data. To obtain accurate resistance factors, calibration of the elastic modulus of the drilled shaft and the equivalent load–displacement curve considering the axial load and elastic settlement was conducted. After determining accurate resistance values, a reliability analysis was performed. The resistance factors were determined to be within 0.13–0.32 of the AASHTO factors for the shaft resistance, 0.19–0.29 for the base resistance, and 0.28–0.42 for the total resistance. This is equivalent to being 30–60% of the AASHTO-recommended values for the shaft resistance and 40–60% of the AASHTO-recommended values for the base resistance. These differences in resistance factors were entirely the result of discrepancies in the conditions of the rock in the US and Korea in which the shafts were founded.

Sonic echo and impulse response tests for length evaluation of soil nails in various bonding mediums

2008 ◽  
Vol 45 (7) ◽  
pp. 1025-1035 ◽  
Author(s):  
Shu-Tao Liao ◽  
Chin-Kuo Huang ◽  
Chung-Yue Wang
Keyword(s):  
Nondestructive Testing ◽  
Impulse Response ◽  
Field Tests ◽  
Drilled Shafts ◽  
Driven Piles ◽  
Soil Nails ◽  
Soil Nail ◽  
Testing Techniques ◽  
Nondestructive Testing Methods

The objective of this paper is to present the results of research for evaluating the installed lengths of soil nails with nondestructive testing methods. Two closely related methods, the sonic echo test and the impulse response test, both of which had been widely applied to assess the integrity of drilled shafts and driven piles, were evaluated to test their capabilities on soil nails. To carry out this study, soil nails of various lengths were embedded in different surrounding materials in the laboratory and then tested with both methods to predict their lengths. The surrounding materials studied in this research included soil and cement grout. Finally, field tests for in situ soil nails were carried out. The results indicated that the relative stiffness of the soil nail to the bond material plays a very important role in the success of testing. It is hoped that through this kind of study, the capability and limitation of using these nondestructive testing techniques to determine the installed lengths or to evaluate the bonding conditions of soil nails can be better understood.

scholarly journals Load and resistance factor design of drilled shafts subjected to lateral loading at service limit state

2018 ◽  
Author(s):  
◽  
Minh Dinh Uong
Keyword(s):  
Limit State ◽  
Design Procedure ◽  
Drilled Shafts ◽  
Resistance Factor ◽  
Lateral Loading ◽  
Drilled Shaft ◽  
Resistance Factors ◽  
Service Limit State ◽  
Load And Resistance Factor ◽  
Aashto Lrfd

Since 2007, the American Association of State Highway Administration Officials (AASHTO) has made utilization of Load and Resistance Factor Design (LRFD) mandatory on all federally-funded new bridge projects (AASHTO, 2007). However, currently, there are no guidelines implementing LRFD techniques for design of drilled shaft subjected to lateral loads using reliability-based analysis. On a national level, the AASHTO LRFD Bridge Design Specifications (AASHTO, 2012) specify that a resistance factor of 1.0 be used for design of drilled shafts subjected to lateral loading at service limit state, which means reliability-based analyses for calibration of resistance factors have not been performed. Therefore, there is a need to create a LRFD procedure for drilled shafts subjected to lateral loading at service limit state that has reliability-based calibrated resistance factors applicable for future projects. The research focuses on the reliability-based analysis of drilled shaft subjected to lateral loading, characterize lateral load transfer model of drilled shafts in shale, probabilistic calibrate resistance factor and contribute to the development of design procedure using LRFD. The objective of this work is to improve the design of drilled shaft subjected to lateral loading using LRFD at service limit state by providing a more reliable design procedure than the current AASHTO LRFD procedure for drilled shafts subjected to lateral loading at service limit state.

scholarly journals Effect of Lateral Cyclic Loading on Drilled Shaft within an MSE Wall

2019 ◽  
Vol 271 ◽  
pp. 02006
Author(s):  
Jie Huang ◽  
Saidur Rahman ◽  
Sazzad Bin-Shafique ◽  
Chao Zheng ◽  
Sandeep Malla
Keyword(s):  
Cyclic Loading ◽  
Numerical Study ◽  
Design Method ◽  
Dissimilar Materials ◽  
Friction Angle ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Lateral Loads ◽  
Mse Wall ◽  
Stress Dependent

Drilled shafts are often subjected to various lateral loads due to earth pressure, wind loads and/or impact loads. Many studies have investigated the behavior of drilled shafts under lateral loads. However, there is limited study on the effect of cyclic loading on drilled shafts, which is of great importance during a hurricane strike. This paper encompasses a numerical study using three-dimensional (3D) finite difference software, FLAC3D, which investigated interaction between a drilled shaft and an MSE wall under cyclic loading event. The backfill material was simulated by a stress-dependent model, which can account for the hardening due to confining stresses. The interactions between dissimilar materials were represented by frictional interface at the contacts. The numerical simulation scrutinized the effects of soil friction angle and the loading cycles on the performance of the drilled shaft and MSE wall under both loading and unloading conditions. The result indicates that the cyclic loading leads to gradual accumulation of the displacement, which cannot be effectively considered in current design method.

Reliability Evaluation of AASHTO Design Equations for Drilled Shafts

1997 ◽  
Vol 1582 (1) ◽  
pp. 60-67
Author(s):  
William M. Isenhower ◽  
James H. Long
Keyword(s):  
Data Base ◽  
Reliability Evaluation ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Factors Affecting ◽  
First Order ◽  
Axial Capacity ◽  
Moment Methods ◽  
First Order Second Moment ◽  
Load Tests

A reliability evaluation of the AASHTO design equations for drilled shafts is described. The evaluation computed the variance of a data base containing load tests to failure on 30 straight-sided drilled shafts using first-order, second-moment methods applied to the AASHTO design equations. The computed variance was compared with the measured variance of the data base. The measured variance was found to exceed the computed variance for approximately 75 percent of the load tests. This is believed to result from important factors affecting the axial capacity of the drilled shaft not being included in the AASHTO design equations. It is speculated that the missing factors are related to common variations in construction practices for drilled shafts.

Evaluation of Thermal Integrity Profiling and Crosshole Sonic Logging for Drilled Shafts with Concrete Defects

2019 ◽  
Vol 2673 (8) ◽  
pp. 86-98
Author(s):  
Andrew Z. Boeckmann ◽  
J. Erik Loehr
Keyword(s):  
Temperature Effect ◽  
Temperature Rise ◽  
Maximum Rate ◽  
Drilled Shafts ◽  
Test Method ◽  
Drilled Shaft ◽  
Integrity Test ◽  
Sonic Logging ◽  
Thermal Integrity

Thermal integrity profiling (TIP), which uses temperatures measured along drilled shafts during concrete curing to identify defects, has recently gained favor as an allowable concrete integrity test method for drilled shafts. Drilled shaft concrete temperatures are theoretically sensitive to defects anywhere within the shaft, which presents an opportunity for improving detection over the widely used crosshole sonic logging (CSL) method. This paper describes investigations conducted to compare detectability from TIP and CSL measurements for various types of defects. TIP and CLS measurements are presented for three full-scale drilled shafts constructed with ten intentional defects varying in location, character, and size. Comparison of these measurements indicates TIP and CSL tests are generally complementary with regard to their detection abilities. Each test method is effective for identifying certain types of defects, but limited or incapable of identifying other types of defects. The paper also includes an evaluation of the role of time on the detectability of TIP interpretations, demonstrating that the temperature effect of defects generally peaks around the time of the maximum rate of temperature rise and decreases significantly thereafter.

scholarly journals Structural analysis of deep soil loosening machine MAS-65

2019 ◽  
Vol 112 ◽  
pp. 03034 ◽  
Author(s):  
Mihai Gabriel Matache ◽  
Remus Marius Oprescu ◽  
Dragos Nicolae Dumitru ◽  
Gabriel Valentin Gheorghe ◽  
Dan Cujbescu ◽  
...  
Keyword(s):  
Structural Analysis ◽  
3D Model ◽  
Structural Integrity ◽  
Field Tests ◽  
Von Mises Stress ◽  
Strain Gages ◽  
Structural Failure ◽  
Deep Soil ◽  
Distribution Maps ◽  
Von Mises

Deep soil loosening machine MAS 65 is destined to work soil at depths exceeding 45 cm, thus the machine’s frame is subjected to loads which could affect its structural integrity. Within this paper a static structural analysis was performed on the machine’s 3D model using finite element method and strain and stress distribution maps were created. Using the Von Mises stress map there were identified several critical points which could fail during normal exploitation conditions and which should be monitored by strain gages during field tests in order to prevent structural failure.

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