Patent RU-2720047-C1 (RU)
Title: Method for erection of bored pile in soil-cement coating
Inventor: SOKOLOV NIKOLAJ SERGEEVICH
IPC: E02D5/34
Filed: 2019-09-23
Granted: 2020-04-23
Abstract: FIELD: construction. 
     SUBSTANCE: invention relates to construction, namely to erection of bored piles in close proximity to standing buildings and constructions, and can be used in formation of pile foundations in weak soils, as well as to strengthen weak soils using jet technology simultaneously with erection of bored piles. Method of erection of bored pile in soil-cement shell includes driving of well with hollow screw with drilling tool equipped with lines supplying high-pressure water-cement solution from pump unit to dispensing element with jet-forming nozzles and system for detecting change of mechanical properties of soils, comprising drilled massif, with subsequent reinforcement, concreting, compaction by pulse discharges and formation of soil-cement shell by means of supply of high-pressure cementing solution through distributing element with jet-forming nozzles. Primer-cement shell is created with variable cross section in accordance with characteristics of soils determined during drilling, wherein shell larger cross-section is formed in areas of reduced mechanical properties of soil by distributing element arranged inside hollow screw with side openings for jet-forming nozzles of dispensing element. Distributing the dispensing element above the drilling tool at a distance providing a time reserve between the drilling and cementation processes required to process information on soil properties, detecting the length of areas of reduced mechanical properties of the massif, forming a command solution for correcting the carbonation mode and switching to carburizing in the new mode, the time margin value is determined from the given relationship T = T 1  + T 2 , where T 1  is the time for detecting the length of areas with reduced or increased mechanical properties of the massif, T 2  is the time for generating a command solution for correcting the carburization conditions and switching to carburizing in the new mode. Time for detecting the length of areas with reduced or increased mechanical properties of array T 1  is determined from the given relationship T 1  = k t  × h/v b , where k t  is coefficient of layer thickness of array with reduced mechanical properties, value is set in the design documentation based on the initial information on the geological structure of the array, h is the thickness of the layer of the massif with reduced mechanical properties, fixed by registration system of change of mechanical properties of soils, which make drilled mass, m, v b  - drilling speed, m/s. Time of formation of command solution for correction of cementation mode and transition to cementation in new mode T 2 , depending on length of located inside the hollow auger supply lines of high-pressure water-cement solution from pump unit to dispensing element, and determined by the given relationship T 2  = k d (L m  + H)/v t , where k d  is a coefficient of time of transition to new cementation conditions, value k d  is given in the design documentation based on the initial information on the material of the high pressure water-cement solution supply lines from the pump unit to the dispensing element, L m  is the length of the lines from the pump unit to the drill string, m, H is drilling depth, m, v t  is average speed of flow of high-pressure solution in mains supplying high-pressure water-cement solution from pump unit to distributing element, m/s. Formation of soil-cement shell is carried out at current drilling speed, and larger diameter of soil-cement shell is performed due to increased pressure of supplied cementing solution, pressure value of which is determined as per specified dependence. After the design depth has been reached by the soil-cement shell, the dispensing element and the drilling tool are removed from the drilled well, and reinforcing frame and discharger are lowered into auger cavity to form high-energy electric pulses for excitation of electric discharges in hardening material, and well is filled with casting consistence to wellhead, After that, gradual lifting of screw (with its unscrewing) is performed and simultaneously concrete mixture is supplied into well (into cavity of hollow screw) until complete formation of formed space. After the hollow auger is lifted, the discharger is gradually lifted, and as it is lifted in the previously identified areas of lower mechanical properties of the ground, pulses are sent to excite electric discharges in the hardening material. 
     EFFECT: technical result consists in reduction of construction time of bored pile in soil-cement cladding with improvement of its strength and bearing properties in weak soils. 
     1 cl, 3 tbl