George E. Veyera

Porewater pressure increases in soil and rock from underground chemical and nuclear explosions

Abstract A review and analysis of chemical and nuclear explosive-induced porewater pressure increases and induced rise in groundwater table elevations (groundwater mounding) is presented. Our analysis indicates that residual pore pressure increases and groundwater mounding can be induced by underground chemical and nuclear explosions to scaled distances of 879 m/(kt) 1 3 . This relationship is linear over seven orders of magnitude of explosive energy ranging from a 0.01 kg chemical explosion to a 100 kt nuclear explosion and is valid for a wide variety of saturated geological profiles. Underground chemical explosions, and probably underground nuclear explosions have the potential to induce liquefaction of water-saturated soils to scaled distances of about 260 m/(kt) 1 3 .

Blast-Induced Stress Wave Propagation and Attenuation: Centrifuge Model Versus Prototype Tests

This paper presents results of centrifuge model studies and full-scale field (prototype) studies designed to provide insights into the influence of water content and the degree of saturation during compaction and testing on high-strain rate loading response of medium dense sand. Objectives of the study were to determine the influence of moisture content at the time of compaction on blast-induced ground shock and stress wave propagation and to compare centrifuge model explosive tests with prototype explosive tests. Model testing was conducted using a geotechnical centrifuge to simulate prototype testing conducted at a field explosives test site. Centrifuge models were constructed at scales of 1/26.3 and 1/18.9 and tested at acceleration levels of 26.3 and 18.9 times earths gravity. Explosives consisting of 3.50 × 10−4 kg (350 mg) and 1.031 × 10−3 kg (1031 mg) of PBX 9407 were buried at depths of 76 mm and 54 mm, respectively. These scaled model tests simulated prototype tests in which 7-kg TNT equivalent explosive charges were detonated at a depth of 1.4 m. Specimens were compacted to a dry density of 1635 kg/m3 at degrees of saturation ranging from 0 to 60 % (water contents from 0 to 14.4 %). Centrifuge model tests and the prototype tests showed similar results. Peak particle velocity, peak stress, and peak scaled acceleration were found to be a function of the degree of saturation with the lowest values at 0 % saturation. Lowest attenuation coefficients occurred in the sand compacted at degrees of saturation of 13 % for the centrifuge tests and 20 % for the prototype tests. Highest attenuation coefficients occurred in the sand compacted dry and at 60 % saturation for all the prototype tests and most of the centrifuge tests. Attenuation coefficients generally decreased with increasing seismic velocities.

An experimental laboratory facility for studying shock-induced liquefaction

Our paper describes a new experimental laboratory apparatus developed to investigate the transient and long-term porewater pressure response of saturated soils subject to compressional stress wave loading. An overview of the laboratory system, the various components, and the experimental procedure followed are presented. Measurements include porewater pressure-time histories for the specimen and total stress time histories for the applied load. Test results indicate that Monterey No. 0/30 sand can be liquefied even at high initial densities and effective stresses under undrained, one-dimensional, confined compressive shock loadings.

Measurement of the Pore Pressure Parameter C Less Than Unity in Saturated Sands

Two saturated sands, Monterey No. 0/30 and Enewetak coral, tested undrained under one-dimensional strain loading, were found to have values of the pore pressure parameter C, less than unity. The C parameter for Monterey No. 0/30 sand, determined to be unity at an effective consolidation stress of 86 kPa, decreased with increasing effective consolidation stress and increasing relative density. A similar behavior was observed for the Enewetak coral sand. These trends are similar to those reported by other researchers for the pore pressure parameter B. The decrease in C parameter values for saturated specimens appears to be a direct result of increasing skeleton stiffness due to increases in effective stress and density. A theoretical analysis of skeleton stiffness based on porosity and pore pressure response predicts similar trends.

An APL function for modeling p -wave induced liquefaction

Abstract This paper presents an APL function that models particle acceleration, velocity, displacement, and porewater pressure responses induced by the passage of compressional waves through water-saturated soil. Inputs to the function include: mass of soil elements, boundary conditions, spring constants, damping ratio, forces applied to the first element, threshold strain and a time increment. Output closely approximates the results of laboratory and field measurements of this phenomenon.

Dilatational-wave-induced pore-water pressure in soil

This paper examines peak and residual pore-water pressures in water-saturated soil induced by a dilatational stress wave. Our new laboratory testing device applies submillisecond, high pressure dilatational stress-wave loadings to water-saturated soil. The soils initial effective stress, density, back pressure and saturation can be controlled with our device. Experimental results show that it is possible to induced residual excess pore-water pressure and liquefaction in water-saturated Monterey No. 0/30 sand. Liquefaction is induced with compressive strains exceeding 0.1 percent for loose samples consolidated at 172 kPa and 1 percent for dense samples consolidated at 690 kPa. Below a threshold compressive strain of about 0.005 percent, no significant residual excess pore-water pressures are developed.