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Article 5 Soil Load Bearing Tests

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§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.
§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:
  1. 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.
  2. 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 = (9S1 /16)(2B/B + 1)2

where:
S = settlement of the larger loaded area (in.)
S1= 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.)

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