Book Description:
Purchase of this book includes free trial access to www.million books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: A foundation of this kind is believed to be as firm and durable as one of the same thickness composed entirely of concrete, while it costs considerably less. Its top surface should slope from the centre to the sides, in order to carry off all the water which percolates through the top layer of stone or gravel, a condition which can be secured either by sloping the road bed, or by selecting the larger or deeper stones for the middle and gradually decreasing their depth toward the sides, thus giving a greater thickness of foundation in the centre than at the sides. It is of capital importance, in a foundation of this description, that the stones should be of such shapes that when set in place their side surfaces will be nearly vertical, or rather will be as nearly perpendicular to the road surface as possible, so that the concrete, after setting, will hold them firmly together, and effectually prevent any upward or downward movement, especially the latter, which might take place if the stones arc of unsuitable shape or improperly set, as shown in Fig. 42. Fie. 42. If the stones very generally, or a great portion of them, are thin and slab like in form, they should be set with their two largest and opposite surfaces cross wise of the road and perpendicular to the road surface, showing in vertical Fig. 43. longitudinal section as in Fig. 43. The concrete will then hold them firmly in place, even upon a wet and spongy road bed. Shell Roads. Upon the South Atlantic and the Gulf coasts of the United States, stone suitable for road coverings does not exist, and in most localities good coarse gravel or pebbles cannot be procured except at such an outlay for transportation as to practically exclude their employment for road construction. Oyster shells, however, ca...
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