Section 27-681
§ 27-681 Applicability. Soil load bearing tests made at the option and
expense of the owner of the proposed structure and inspected in
accordance with the provisions of section 27-132 of article seven of
subchapter one of this chapter, controlled inspection, may be accepted
by the commissioner as evidence of allowable bearing capacity of a given
soil stratum, subject to the following limitations:
(a) The applicability of soil load bearing tests shall be limited to
soil materials of classes 5-65 through 10-65.
(b) Soil load bearing tests shall not be used to justify allowable
bearing pressures in excess of the maximum allowable bearing values
established in table 11-2 for the applicable class of material.
(c) Soil load bearing tests shall not be applicable where the proposed
bearing stratum is underlain by a stratum of lower class, unless
analysis indicates that the presence of such lower stratum will not
create excessive settlements of the building.
Section 27-682
§ 27-682 Procedure. (a) Preparations. (1) A sketch showing the layout,
levels, number of tests, details of test apparatus, and test procedures
shall be filed with the commissioner before conducting such tests. The
sketch shall also include the locations and levels of the proposed tests
in relation to the contemplated foundation levels as well as the logs of
borings that have been made for the building or buildings involved.
(2) The tests shall be made at the levels contemplated for the
proposed building footings, and in at least two locations within the
limits of the building area. The surfaces at the locations of the
proposed tests shall be leveled at the elevations of the proposed test
for a clear distance of at least five feet all around the test plate.
(3) The loaded area shall be square and at least twenty-four inches by
twenty-four inches.
(4) When load tests are performed on materials affected by drying,
suitable methods shall be used to prevent evaporation from the material.
(5) In the event ground water is present immediatley below, at, or
above the level required to be tested, dewatering facilities shall be
installed to maintain ground water a minimum of four feet below the
level of the test plate during the preparation and duration of the test
or tests.
(6) Trenches and other provisions at the ground surface shall be made
to prevent inflow of surface water and to remove water that may drain
into the test area. The entire test area shall be protected against
weather and rainfall for the entire duration of the test.
(7) The load platform providing the support for the test load shall be
supported on adequate timber cribbing, which shall not be closer than
five feet from the edge of the test plate.
(8) The plate on which the loads are applied shall be of steel having
a minimum thickness of two inches and shall be set and centered in a
depression in the bottom of the pit or loading area about thirty inches
square for a twenty-four inch by twenty-four inch plate and eight inches
deep. The area on which the plate is placed shall be scraped to remove
any disturbed soil. The area to be tested shall be covered with a thin
layer of fine clean sand that shall be smoothed and leveled until a
completely level surface for placing the test plate is obtained.
(9) Settlement observations shall be made at four corners of test
plate by means of dial extensometers. The extensometers shall provide
readings to the nearest 0.001 in. In addition, settlement observations
shall be taken using an engineer's level reading to 0.001 ft., properly
referenced to a well-established benchmark.
(10) All tests shall be made under the surveillance of the
commissioner, who shall be duly notified in order that he or she may be
represented.
(b) Loading of the soil.
(1) Loads shall be applied to the test plate by direct weight or by
means of a hydraulic jack. The loading platform or box shall be
constructed to provide a concentric load on the plate. If direct weight
is employed, the loading increments shall be applied without impact or
jar.
The weight of the blocking placed on the plate and the loading
platform or box shall be obtained prior to the test and this weight
shall be considered as the first increment of load. If a hydraulic jack
is employed, facilities for maintaining each increment of desired load
constant under increasing settlement shall be provided. The gauge for
the jack and the jack shall be calibrated as a unit not more than two
weeks prior to the test.
(2) The unit intensity of the test load shall be one and one-half
times the unit intensity of the loading proposed to be imposed on the
soil by the design loads. The test load shall be applied in a minimum of
six increments at twenty-five percent, fifty percent, seventy-five
percent, one hundred percent, one hundred twenty-five percent, and one
hundred fifty percent of the proposed working load. Each load increment
shall be maintained for a length of time as follows:
a. At the proposed loading and at one hundred fifty percent of load
until the settlement is less than 0.005 in. over a period of twenty-four
hours.
b. At other loadings until the settlement is 0.001 in. or less, over a
period of five minutes.
(3) Under each load increment, settlement observations shall be made
and recorded at intervals of one-half minute, one minute, four minutes,
and each four minutes thereafter after application of load increment
except in the instance of the working load and one hundred fifty percent
of working load where, after the four minute reading, the time interval
shall be doubled successively until the final settlement limitation is
reached and the load is increased or removed.
(4) After the test load and limiting rate of settlement under the test
load is reached, loads shall be removed in not less than three equal
increments and rebound observations made in the same manner as for the
loading increments. The final rebound shall be recorded twenty-four
hours after the entire test load has been removed.
(c) Determination of results.
(1) Subject to the limitations designated in section 27-681 of this
article, the soil load test for soils of classes 5-65 through 8-65 shall
be considered as tentatively substantiating the ability of the soil to
support the proposed unit intensity of loading if the gross settlement
of the test plate under the proposed unit intensity of loading does not
exceed one-half inch and the total gross settlement after the fifty
percent overload is applied does not exceed one inch. This tentative
substantiation shall be supported by a report by the architect or
engineer on the correlation of the behavior of the load test to the
probable behavior of the full size building. The proposed design load
shall be considered as acceptable only upon written acceptance by the
commissioner.
(2) For soils of classes 9-65 and 10-65, the soil load test alone
shall not be considered as evidence of allowable bearing capacity of the
soil, but the data so obtained may be utilized to establish an allowable
bearing capacity subject to the provisions of section 27-677 and 27-678
of article four of this subchapter.
(3) In the event that it is desired to conduct load tests on square
areas larger than the minimum stipulated above, permission may be
granted provided notice of such increase in area is properly filed with
the test information required to be submitted to the commissioner. The
limiting gross settlements stipulated in paragraph one of this
subdivision shall be increased in relation to the increase in width of
test plate in accordance with the following formula:
S = (9S{1}/16)(2B/B + 1){2}
where: S = settlement of the larger loaded area (in.)
S{1} = permissible settlement of twenty-four inch by twenty-four
inch loaded area, as specified in paragraph one of this
subdivision (in.)
B = side dimension of square plate used for test (ft.).
To the extent possible under law, Friends of Devin Balkind for Public Advocate has waived all copyright and related or neighboring rights to New York City Administrative Code. This work is published from: United States.
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