2006 New York Code - Bearing Capacity Of Nominally Unsatisfactory Bearing Materials.

 
    §   27-679   Bearing  capacity  of  nominally  unsatisfactory  bearing
  materials.    Whenever  soils  exploration  shows  that   the   proposed
  foundation  would  rest on, or be underlain by, nominally unsatisfactory
  bearing materials, a report based on soil tests and foundation  analysis
  (including  analysis  of  undisturbed  samples) shall be submitted by an
  architect or engineer, demonstrating, subject to  the  approval  of  the
  commissioner,  that  the proposed construction, under a condition of one
  hundred  percent  over  load,  is  safe  against  failure  of  the  soil
  materials.  The report shall also show that the probable total magnitude
  and distribution of settlement to be expected  under  design  conditions
  will  not  result  in  instability  of  the  building or stresses in the
  structure in excess of the allowable values  established  in  subchapter
  ten of this chapter. In addition, the following provisions shall apply:
    (a) Fill materials.
    (1)  CONTROLLED  FILLS.  Fills  shall  be  considered  as satisfactory
  bearing materials of class 6-65 or 7-65 when placed in  accordance  with
  the   following   procedures,   under   the  provisions  for  controlled
  inspection.
    a. Before placement of fill, the  existing  ground  surface  shall  be
  stripped  of  all  organic  growth,  timber,  rubbish, and debris. After
  stripping, the ground surface shall  be  compacted  to  the  density  in
  subparagraph d of this paragraph.
    b.  Materials  for  fill shall consist of sand, gravel, crushed stone,
  crushed gravel, or a mixture of these,  and  shall  contain  no  organic
  matter.  The  fill  materials  shall contain no particles exceeding four
  inches in the largest dimension. No more than thirty  per  cent  of  the
  material  shall  be retained on a three-quarter inch sieve. The material
  passing the three quarter inch sieve shall contain, by weight,  no  more
  than  forty  percent  passing  the  one hundred sieve, or twelve percent
  passing the two hundred sieve.
    c. The grading of the fill shall be determined in accordance with  the
  applicable procedures of reference standards RS 11-1 and RS 11-2.
    d. Fill shall be placed and compacted at its optimum moisture content,
  in  uniform  layers not more than twelve inches thick (after compaction)
  and each layer shall be thoroughly compacted to a density not less  than
  ninety-five  percent  of the density prescribed in reference standard RS
  11-3. The field density shall be verified by in-place density tests made
  on each lift of the embankment. Fill shall not be placed when frozen  or
  placed on a frozen or wet sub-grade.
    (2) UNCONTROLLED FILLS. Fill material, other than controlled fill, may
  be  used  for  the  support of buildings, other than one- and two-family
  dwellings, and may be considered as  satisfactory  bearing  material  of
  applicable class, subject to the following:
    a.  The  soil  within  the  building area shall be explored using test
  pits.  At least one test pit, penetrating at least eight feet below  the
  level  of  the  bottom  of  the proposed footings, shall be provided for
  every twenty-five hundred square feet of building area. Where such  test
  pits consistently indicate that the fill is composed of material that is
  free of voids and free of extensive inclusions of mud, organic materials
  such  as  paper,  garbage,  cans,  or  metallic objects, and debris, the
  provisions of subparagraphs b and c of this paragraph shall apply. Where
  the test pits show such voids or inclusions, the  additional  provisions
  of  subparagraph d of this paragraph shall apply. Borings may be used in
  lieu of test pits, provided that continuous samples at least four inches
  in diameter are recovered.
    b. The building area shall be additionally explored using one standard
  boring under each column. These borings shall  be  carried  to  a  depth
  sufficient  to  penetrate  into natural ground, but not less than twenty


  feet below grade, and a sufficient number shall  penetrate  deeper  than
  twenty  feet  as  required  to  meet the provisions of section 27-663 of
  article two of  this  subchapter.  Where  such  borings  show  voids  or
  inclusions,  the  provisions  of  subparagraph d of this paragraph shall
  apply.
    c. The allowable soil bearing pressure on the fill material shall  not
  exceed two tons per square foot.
    d.  Wherever  the  fill  shows  voids  or  inclusions  as described in
  subparagraphs a and b of this paragraph either the fill shall be treated
  as having  no  presumptive  bearing  capacity,  or  the  building  shall
  incorporate  adequate  strength  and  stiffness  to bridge such voids or
  inclusions or shall be articulated to prevent damage due to differential
  or localized settlement of the fill.
    (b) Organic silts, organic clays, soft inorganic clay, loose inorganic
  silt, and varved silt.
    (1) The allowable bearing pressure shall be  determined  independently
  of table 11-2 subject to the following:
    a.  For  varved  silts,  the  soil  bearing  pressure  produced by the
  proposed building shall not exceed two tons per square foot, except that
  for desiccated or preconsolidated soils, higher bearing  pressures  will
  be allowed.
    b.  For organic silts or clays (groups OL and OH) or for soft or loose
  soils of groups ML, CL, MH, and CH, the soil bearing  pressure  produced
  by the proposed building shall not exceed one ton per square foot except
  that a value of two tons per square foot will be permitted on soils that
  are adequately preconsolidated or artificially treated.
    (2)  The  report required in this section shall contain, as a minimum,
  the following information:
    a. Geological profiles through the area defining the stratigraphy.
    b. Sufficient laboratory test data on  the  compressible  material  to
  indicate    the    coefficient    of   consolidation,   coefficient   of
  compressibility, permeability,  secondary  compression  characteristics,
  and Atterberg limits.
    c.  Where  the  design contemplates improvement of the natural bearing
  capacity and/or reduction in settlements by virtue of preloading,  cross
  sections showing the amount of fill and surcharge to be placed on design
  details  showing  the  required time for surcharging shall be indicated,
  and computations showing the amount of settlement to be expected  during
  surcharging.  Records  of  settlement plate elevations and pore pressure
  readings, before, during, and after surcharging, shall be filed with the
  commissioner.
    d. The estimated amount and rate of settlement expected to occur after
  the structure has been completed, including the influence  of  dead  and
  live loads of the structure.
    e.  A detailed analysis showing that the anticipated future settlement
  will not adversely affect the performance of the structure.
    f. Where  sand  drains  are  to  be  used,  computations  showing  the
  diameter,  spacing,  and method of installation of such drains, shall be
  provided.
    (c)  Artificially  treated  soils.   Nominally   unsatisfactory   soil
  materials  that are artificially compacted, cemented, or preconsolidated
  (including soils compacted by vibration, cemented by chemical injection,
  or preconsolidated by use of electric current, but not  including  cases
  where  preconsolidation  consists solely of the use of surcharge with or
  without sand drains) may be used  for  the  support  of  buildings,  and
  nominally  satisfactory soil materials that are similarly treated may be
  used to resist soil bearing pressures in excess of  those  indicated  in
  table 11-2 for the soil in its natural state, subject to the following:


    (1)  The  vertical  and  lateral extent of the soil that is compacted,
  cemented, or preconsolidated shall conform to the  full  extent  of  the
  distribution  of  loading  that is assumed for purposes of computing the
  intensities of the  soil  bearing  pressure.  The  actual  soil  bearing
  pressure shall not exceed the limitations of subdivisions (a) and (b) of
  this  section  for  nominally  unsatisfactory  bearing materials or, for
  satisfactory bearing materials, shall  not  exceed  the  limitations  of
  table 11-2.
    (2)  After  the  treatment procedure, a minimum of one boring shall be
  made for every sixteen hundred  square  feet  of  that  portion  of  the
  building area that is supported on treated soil, and a sufficient number
  of  samples  shall be recovered from the treated soil to demonstrate the
  efficacy of the treatment.