during final placing, or by other methods of placement which will produce 

 the specified results. Rearranging of individual stones by mechanical 

 equipment or by hand may be required to obtain a reasonably well-graded 

 distribution of stone sizes. Pushing material up the slope or dumping down 

 the slope should not be permitted. 



f. Other Stones . Stones to be used as filler material or toe protec- 

 tion stone should be distributed evenly over the required area. Filler 

 stone can be placed on and dumped with core material. Toe protection stone 

 should be placed so as to produce a reasonably well-graded mass of stone 

 with the minimum practicable percentage of voids. Larger stone should be 

 well distributed. 



Chink stone should be spread uniformly to form a fairly flat surface, 

 even with the top of the riprap. Placing of materials which tend to segre- 

 gate particle size should not be permitted. Placement of chink stone may 

 be by hand. In this case the stone should be forced into the riprap voids 

 by rodding, spading, or other satisfactory methods. 



6. Repair of Structures . 



One of the advantages of stone structures is that they are relatively 

 flexible and are not easily impaired nor weakened by slight movement 

 resulting from settlement or other minor adjustments. Damage to stone 

 structures generally consists of wearing, erosion, dislodging, or removal 

 of the stone. The repair consists primarily of rebuilding the stone 

 structure or replacing the stone with new material. In some cases repair 

 can be achieved with concrete or asphalt grout. 



7. Environmental Considerations . 



a. General . In its natural environment, most of the varieties of 

 stone normally used in coastal structures are very durable, taking centuries 

 to erode and become part of the sediments of the earth. In coastal struc- 

 tures, this property of durability plus its density is what makes stone a 

 valuable material. Except for the environmental considerations specifically 

 discussed, stone is not significantly affected by the coastal environment. 



b. Periodic Wetting and Drying . The gain or loss of moisture when a 

 stone is alternately exposed to a damp or wet situation and then dried will 

 be the most rapid if the pores are large or straight, and least rapid if 

 they are small or tortuous. The leaching action of water which is not 

 chemically combined may remove cementing materials from the stone and 

 weaken it. 



c. Freezing and Thawing . Freezing and thawing whether in fresh or 

 salt water can affect the durability of stone. For example, if water is 

 absorbed in the pores of stone and is subsequently frozen, it will expand. 

 The forces developed in filled pores will cause the stone to crack or 

 spall, and the porosity will be increased. As the pores grow, repetition 

 of each cycle will damage the rock. Stone can be disintegrated by freezing 

 and thawing only if the pores are virtually filled with water. 



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