Slope Stability Analysis: A Computerized Solution of Bishop’s Simplified Method of Slices

A computer program based on Bishop\u27s simplified method of slices (1954) and capable of analyzing the slope stability of a multilayered soil mass is described. The computer program was specifically developed for analyzing the slope stability of highway bridge approach embankments; however, it can be applied to a broad spectrum of practical slope configurations and bearing capacity problems. Details of the use, applications, and accuracy of the program are presented. Important features of the computer program include a grid type, search operation for locating the critical shear surface and a ledger printout of the forces acting on each individual slice. The latter feature was included so that results of the computer program could be compared to those obtained from manual computations. Pore pressures in the computer program are handled in a manner described by Bishop (1954). Additionally, for seepage cases, infinite slope conditions are assumed and used to simulate a flow net

Remedial Stability Analysis of Unstable Eastern Approach Embankment, Bluegrass Parkway Bridges over Chaplin River

In a meeting held on March 7, 1973, the Division of Research was requested to perform a supplementary slope stability analysis of the unstable, eastern approach embankment and foundation located at the crossing of the Bluegrass Parkway over Chaplin River and extending between Stations 2317+14 and 2321+00. Previously (see referenced report), two remedial schemes had been considered for increasing the stability of the unstable soil mass to an acceptable level. Those included: 1) loading the toe area of the existing, eastern approach slope with a berm, including a sloping berm, and 2) unloading the upper portion of the eastern slope by excavation, that is, decreasing the original approach slope (1.5 horizontal to 1 vertical), which would require an extension of the bridges, construction of piers at the present locations of the abutments and a relocation of the abutments. In the report cited, consideration was given primarily to using a berm to stabilize the eastern approach slope. Normally, that method of increasing the stability of an unstable embankment is the most economical. However, loading the toe area of the existing slope with a berm was considered undesirable in the meeting of March 7, 1973, because a berm would extend into the Chaplin River channel and alter channel hydraulics by constricting the channel area. Furthermore, there was a question of whether the berm materials could withstand the high velocities of Chaplin River. Consequently, an in-depth stability analysis was performed which involved excavation of the approach embankment and a relocation of the abutments

Carbon Structure Hazard Control

Carbon composite structures are widely used in virtually all advanced technology industries for a multitude of applications. The high strength-to-weight ratio and resistance to aggressive service environments make them highly desirable. Automotive, aerospace, and petroleum industries extensively use, and will continue to use, this enabling technology. As a result of this broad range of use, field and test personnel are increasingly exposed to hazards associated with these structures. No single published document exists to address the hazards and make recommendations for the hazard controls required for the different exposure possibilities from damaged structures including airborne fibers, fly, and dust. The potential for personnel exposure varies depending on the application or manipulation of the structure. The effect of exposure to carbon hazards is not limited to personnel, protection of electronics and mechanical equipment must be considered as well. The various exposure opportunities defined in this document include pre-manufacturing fly and dust, the cured structure, manufacturing/machining, post-event cleanup, and post-event test and/or evaluation. Hazard control is defined as it is applicable or applied for the specific exposure opportunity. The carbon exposure hazard includes fly, dust, fiber (cured/uncured), and matrix vapor/thermal decomposition products. By using the recommendations in this document, a high level of confidence can be assured for the protection of personnel and equipment

Hypervelocity Impact of Composite Overwrap Pressure Vessels

There is a limited amount of hypervelocity impact (HVI) data on pressurized composite overwrapped pressure vessels (COPV). In recent years, NASA has performed HVI tests to characterize impact conditions resulting in either leak or burst of the COPVs representative of spacecraft hardware. This paper reports on the results of 40 tests that have been conducted on several types of COPV configurations, pressurized by inert gas to near the vessels rated maximum expected operating pressure (MEOP). These tests were used to better understand COPV response under HVI conditions and develop ballistic limit equations (BLE) related to these tests

Stability of a Side-Hill Embankment

The report submitted herein is a case history describing observations and in-depth analyses made at a highway site involving a massive, unstable side-hill embankment located on I-64 in Boyd County. The in-depth study was initiated in January 1973. The I-64 site was selected for study because it contained several design, construction and maintenance features as well as soil types that are typical of many highway embankments in Kentucky. Side-hill fill situations are common design problems and oftentimes have required extensive maintenance after construction. Major objectives of the study were to 1) determine the causes of instability of the I-64 embankment, 2) check a remedial solution previously reported for the I-64 site and present alternative solutions if necessary, 3) determine short-term (initial) and long-term safety factors of the embankment slopes, and 4) compare theoretical shear surfaces obtained from a slope stability program based on Bishop\u27s simplified method of slices with actual failure points obtained from slope indicators and surface observations. All slope stability computations were carried out in terms of effective stress using shear strength parameters obtained from consolidated, isotropic, undrained triaxial tests with pore pressure measurements

Inspection for Damage to Carbon/Epoxy Composite Overwrapped Pressure Vessels

Objective: To train aerospace flight hardware visual inspectors detect visible damage to the composite shell of Graphite/Epoxy COPVs

Experimental Investigation of the Shuttle Transportation System Composite Overwrapped Pressure Vessels for Stress Rupture Life

A viewgraph presentation describing stress rupture testing on Composite Overwrapped Pressure Vessels (COPV) is shown. The topics include: 1) Purpose for Testing; 2) NASA WSTF COPV Test Program; 3) NASA WSTF Test Facilities; 4) COPV Impact Study; 5) Fluids Compatibility Testing; 6) Stress Rupture Testing; and 7) COPV Lifting

Stress Rupture Testing and Analysis of the NASA WSTF-JPL Carbon Overwrapped Pressure Vessels

Carbon composite overwrapped pressure vessels (COPVs) are widely used in applications from spacecraft to life support. COPV technology provides a pressurized media storage advantage over amorphous technology with weight savings on the order of 30 percent. The National Aeronautics and Space Administration (NASA) has been supporting the development of this technology since the early 1970's with an interest in safe application of these components to reduce mass to orbit. NASA White Sands Test Facility (WSTF) has been testing components in support of this objective since the 1980s and has been involved in test development and analysis to address affects of impact, propellant and cryogenic fluids exposure on Kevlar and carbon epoxy. The focus of this paper is to present results of a recent joint WSTF-Jet Propulsion Laboratories (JPL) effort to assess safe life of these components. The WSTF-JPL test articles consisted of an aluminum liner and a carbon fiber overwrap in an industry standard epoxy resin system. The vessels were specifically designed with one plus-minus helical wrap and one hoop wrap over the helical and they measured 4.23 x 11.4 in. long. 120 test articles were manufactured in August of 1998 of one lot fiber and resin and the 110 test articles were delivered to WSTF for test. Ten of the 120 test articles were burst tested at the manufacturer to establish the delivered fiber stress. Figure 1 shows a test article in a pre burst condition and with a hoop fiber failure (no leak of pressurized media) and post burst (failure of liner and loss of pressurized media)

Composite Overwrapped Pressure Vessels (COPV) Stress Rupture Test

One of the major concerns for the aging Space Shuttle fleet is the stress rupture life of composite overwrapped pressure vessels (COPVs). Stress rupture life of a COPV has been defined as the minimum time during which the composite maintains structural integrity considering the combined effects of stress levels and time. To assist in the evaluation of the aging COPVs in the Orbiter fleet an analytical reliability model was developed. The actual data used to construct this model was from testing of COPVs constructed of similar, but not exactly same materials and pressure cycles as used on Orbiter vessels. Since no actual Orbiter COPV stress rupture data exists the Space Shuttle Program decided to run a stress rupture test to compare to model predictions. Due to availability of spares, the testing was unfortunately limited to one 40" vessel. The stress rupture test was performed at maximum operating pressure at an elevated temperature to accelerate aging. The test was performed in two phases. The first phase, 130 F, a moderately accelerated test designed to achieve the midpoint of the model predicted point reliability. The more aggressive second phase, performed at 160 F was designed to determine if the test article will exceed the 95% confidence interval of the model. This paper will discuss the results of this test, it's implications and possible follow-on testing

Composite Overwrapped Pressure Vessels (COPV) Stress Rupture Test: Part 2

One of the major concerns for the aging Space Shuttle fleet is the stress rupture life of composite overwrapped pressure vessels (COPVs). Stress rupture life of a COPY has been defined as the minimum time during which the composite maintains structural integrity considering the combined effects of stress levels and time. To assist in the evaluation of the aging COPVs in the Orbiter fleet an analytical reliability model was developed. The actual data used to construct this model was from testing of COPVs constructed of similar, but not exactly same materials and pressure cycles as used on Orbiter vessels. Since no actual Orbiter COPV stress rupture data exists the Space Shuttle Program decided to run a stress rupture test to compare to model predictions. Due to availability of spares, the testing was unfortunately limited to one 40" vessel. The stress rupture test was performed at maximum operating pressure at an elevated temperature to accelerate aging. The test was performed in two phases. The first phase, 130 F, a moderately accelerated test designed to achieve the midpoint of the model predicted point reliability. A more aggressive second phase, performed at 160 F, was designed to determine if the test article will exceed the 95% confidence interval ofthe model. In phase 3, the vessel pressure was increased to above maximum operating pressure while maintaining the phase 2 temperature. After reaching enough effectives hours to reach the 99.99% confidence level of the model phase 4 testing began when the temperature was increased to greater than 170 F. The vessel was maintained at phase 4 conditions until it failed after over 3 million effect hours. This paper will discuss the results of this test, it's implications and possible follow-on testing