Deep building pit trussed-beam inner support integral application pre-stress method

[0032] Embodiment 1: see figure 1. This embodiment includes the following steps: (1) install the crown beam or waist beam 1 in the deep foundation pit, install the main top strut 2, the diagonal bar 3 and the web bar 4 to form a truss-type internal support, and install the above-mentioned truss-type internal support Installed between two opposite pit walls in the deep foundation pit; (2) On each main top strut 2, a prestressed force transmission seat is installed along the axial direction of the main top strut 2, and the prestressed force transmission seat It is composed of corbels 8 and stiffeners 7 welded on both sides of the main top strut 2; (3) a jack 5 or Jack group, and apply a certain prestress first or not apply prestress first, apply a certain prestress first to avoid the phenomenon of sudden increase in deformation after cutting off the main top strut; (4) Cut off each main top strut The main top strut 2 between the corbels 8 on both sides is prestressed with the jack 5. When the prestress to be applied is reached, it is stabilized for a period of time, and then the main top strut 2 due to the prestress is applied immediately. The gap 6 is reinforced and welded firmly with a steel plate. The jack 5 or the jack group can be removed or not, and the jack 5 or the jack group is retained during the use stage of the inner support, which can play a role in adjusting the force.

[0033] Example 2: see figure 1 , figure 2 and image 3. The steps of this embodiment are basically the same as those of Embodiment 1, the difference being that for a foundation pit with a large span, it is necessary to install the truss-type internal support described in step (1) of Embodiment 1 before connecting with each main support. Set the column 11 fixed in the column pile below the bottom surface of the deep foundation pit at the corresponding place where the jack is installed on the pole 2, set the tray 12 on the upper end of the column 11, the tray 12 and the column 11 are welded firmly, and set the fixture 13 at each column tray Before the overall prestressing of the truss-type inner support in Embodiment 1, the main top struts 2 at both ends of the jack 5 are respectively fixed on the pallet 12 with the fixture 13, so as to prevent the truss-type inner support from bulging upwards.

[0034] Embodiment 3: see figure 1 and Figure 4 , this embodiment is realized on the basis of embodiment 1 or embodiment 2, and its steps are basically the same as embodiment 1 or embodiment 2, the difference is that two or more roots in the above two embodiments Corbels 9 are arranged at the connection between the main top brace 2 and the crown beam or waist beam 1, and the corbel 9 is welded to the crown beam or waist beam 1 or the vertical structure 14 of the foundation pit. Two or more main top braces 2 The ends are respectively placed on the corbels 9, and a gap 10 of about 1 cm is maintained with the crown beam or the waist beam 1. The purpose is to ensure that the two or four oblique rods 3 are stressed first and gradually increased when the prestress is applied. , and then according to the size of the force monitoring results at these two or four inclined bars 3 places, determine the timing of closing the gap between two or more main top struts 2 and the crown beam or waist beam 1.