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    <title>Transport Research International Documentation (TRID)</title>
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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>THE PROMISE OF TUNNELING BY ELECTRON BEAM</title>
      <link>https://trid.trb.org/View/126033</link>
      <description><![CDATA[TUNNELING THROUGH ROCK IS A SLOW PROCEDURE. FOR EACH ADVANCE, HOLES MUST BE DRILLED AND EXPLOSIVE CHARGES SET. THEN PEOPLE ARE CLEARED FROM THE AREA AND THE CHARGES ARE DETONATED. THE DEBRIS IS REMOVED AND THE CYCLE STARTS AGAIN. EXPERIMENTS IN PROGRESS AT THE LAWRENCE BERKLEY LABORATORY IN CALIFORNIA SHOW PROMISE OF SPEEDING UP ROCK TUNNELING BY USING INTENSE BEAMS OF ELECTRONS TO CUT THROUGH THE ROCK. THE WORK IS SUPPORTED BY THE NATIONAL SCIENCE FOUNDATION AS PART OF ITS RESEARCH APPLIED TO NATIONAL NEEDS PROGRAM (RANN). THE ELECTRONS COME FROM ACCELERATORS THAT ARE QUITE LOW-ENERGY BY TODAY'S STANDARDS -- ABOUT ONE MILLION ELECTRON-VOLTS (ONE MEV). THESE MACHINES PRODUCE BURSTS OF ELECTRONS MANY TIMES MORE INTENSE THAN THOSE USED IN PARTICLE PHYSICS EXPERIMENTS. THE BURSTS, WHICH LAST ONLY 50 NANOSECONDS (ONE TWENTY- MILLIONTH OF A SECOND), DELIVER INTENSE PULSES OF HEAT TO THE ROCK. THIS SETS UP A THERMAL EXPANSION WAVE IN THE ROCK. A SINGLE BURST DOES NOT FLAKE OFF VERY MUCH, ONLY A FEW CENTIMETERS, BUT REPETITION RATES OF HUNDREDS OF TIMES A SECOND ARE POSSIBLE. FOR A WORKING MODEL AN APPARATUS IS ENVISIONED ABOUT THE SIZE OF THE MOLE MACHINES THAT NOW DO EARTH TUNNELING. THIS WOULD SCAN A FOUR- OR FIVE- MEV BEAM ACROSS THE ROCK FACE. AT SEVERAL HUNDRED BURSTS A SECOND IT COULD CHIP OFF A SIZABLE QUANTITY OF ROCK IN A TIME THAT IS SHORT BY HUMAN STANDARDS.]]></description>
      <pubDate>Fri, 28 Sep 1973 00:00:00 GMT</pubDate>
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      <title>RESEARCHERS BREAK ROCK WITH ELECTRON BURSTS</title>
      <link>https://trid.trb.org/View/109472</link>
      <description><![CDATA[IT IS CLAIMED THAT "AN INTENSE ELECTRON BURST OF MODEST ENERGY" PRODUCES A SIGNIFICANT CRATERING EFFECT IN GRANITE,LIMESTONE,BASALT AND SANDSTONE. THE EFFECT OF THE MACHINE-GUN-LIKE BURSTS OF ELECTRONS IS EVEN GREATER IF THE ROCK IS WET. ELECTRON ACCELERATORS DIGGING RAPIDLY THROUGH ROCK BY PULVERIZING IT WITH INTENSE PULSES OF ENERGY FIRED HUNDREDS OF TIMES A SECOND ARE ENVISIONED. THE DEVELOPMENT OF ACCELERATORS THAT WOULD BE PRACTICAL CONSTRUCTION TOOLS WILL BE A TECHNOLOGICAL CHALLENGE AND THE BIGGEST TECHNICAL PROBLEM WOULD BE HOW TO FIRE HUNDREDS OF PULSES A SECOND. LABORATORY STUDIES OF POSSIBLE ELECTRON DAMAGE TO THE STRUCTURE OF AN ELECTRON RING ACCELERATOR, MAINLY THE SPALLING OF CONCRETE, LED TO THIS DISCOVERY WHICH COULD BE A MAJOR BREAKTHROUGH IN UNDERGROUND EXCAVATION.]]></description>
      <pubDate>Fri, 31 Aug 1973 00:00:00 GMT</pubDate>
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