foundations and quarry blasting

[crystal074]

I need some answers,Please. I am trying to fight a development which is being built on a mountain top. This site has very steep slopes.I will try and give you all information needed to answer my questions.Soils:Hibernia etra sandy loam,3-15%slopes(HpC),Muck,shallow(Ms); Ridgebury extra loam,0-3%slopes(RbA),3-8% slopes(RbB);Riverhead sandy loam,3-8% slopes(RhB);Rock outcrop Rockaway complex, 15-35% slopes(RxE);and Rockaway complex-Rock outcrop, 3-15% slopes(RsC)-with exceptions of the roads,which occassionally cross steeper sloping portions of the site,the vast majority of the proposed construction will occur on areas of the site having slopes less than 15%. Where required,steep slope areas will be graded to a shallower slope ratios to accomodate construction.

Now on this same mountain ,about 1,500 to 2,000 feet away is an active quarry. This quarry blasts at least 2x a week. The homes that are not on this mountain feel the tremors and their homes shake. Wouldn't there be adverse impacts to these new townhomes and their foundations?What could be the impacts? How could the foundations be made to with stand the quarry? SHould this applicant hire a geo-technical engineer? If so, please give reasons as to why. I am really trying to learn all information to make sure that the safety of the people that move into these homes are a priority. Thank you so much!

 

[ishvaaag]

Really the blasting being noticeable in akin site points to the convenience of hiring expert advice, especially to appreciate if there's some risk of general failures not so easily ascertainable by civil or structural engineering knowledge.

If such general failure does not happen, the good point is that there being typical blast twice a week the para-seismic events should be statistically definible, what experts in characterizing the ground (and other) seismic accelerations can also well do. Basically I assume this must consist in taking readings of accelerometers at your site whilst blasting, then producing a safe envelope in accord with the geotecthnical and structural engineering relevant parameters.

 

[phillyfrank]

See my posting under Geotechnical Engineering.

 

[Rowland33]

The soils are not described in geotechnical terms but the slopes sound conservative, again the rock slopes sound reasonable unless jointing or faulting is present, (especially if there is a spring line along a joint or fault.)
Vibrations from the blasting from the quarry may be disturbing but will not necessarily do damage to a structure, the human body is sensitve to vibrations. I agree with Ishvaag, a safe perimeter can be established and I believe that structures 1500 feet from the quarry would not be subject to damage unless the quarry are using excessive amounts of explosive. Since the quarry is there first Human annoyance from the explosions after construction is not a valid complaint.
Steep slopes that are to be filled should be benched to ensure against future slippage.

In most duristictions a Geotechnical report is required before construction permission is granted.
Reasons why this is needed in your case:
1. Stability of filled slopes
2. Geotechnical assessment of rock slope stability
3. Foundation design stratergy of indevidaul structues, i.e. All on rock, consider jointing or perhaps faulting. All on soil, consider frost heave. On soil and rock,consider differential movement.
4. Effects of filling, excavation and possibly blasting on subsurface ground water movement. Are these dwellings to be served by water wells?
5. What provision is to be made for sewage removal? Will this entail holdng tank and tile field drainage? Is the soil suitable for tile fields?
6. Effect of quarry blasting, do the foundations nead to be reinforced? (I doubt it but it should be considered.
7. Geotechnical opinion on road design, special conditions may be required for the soil to rock interphase.