Method for treating sludge backfill foundation through dynamic compaction replacement treatment

Abstract

The invention relates to the technical field of foundation treatment, in particular to a dynamic compaction replacement treatment sludge backfill foundation treatment method, by excavating a first sludge outlet and a second sludge outlet respectively during two times of point compaction replacement construction, sludge can be discharged from the first sludge outlet and the second sludge outlet, the internal pressure of a site is reduced, and the construction efficiency is improved. By gradually increasing the replacement energy level, carrying out point compaction replacement twice, then carrying out full compaction and rolling for six times after compaction, the construction safety is improved, a muddy soil layer is penetrated, the replacement depth reaches 8 m, the feeding depth of a replacement material is increased, soft soil is reinforced and compacted, a replacement pier body is formed, the integrity of a foundation is improved, and the construction period is shortened. Therefore, the bearing capacity and the compression modulus of the foundation are improved, the purpose of foundation treatment is achieved, and the method is low in cost and short in period.

Description

Technical Field

[0001] The invention relates to the technical field of foundation treatment, and in particular to a method for treating a sludge backfill foundation by dynamic compaction replacement. Background Art

[0002] In the wave of economic boom, land reclamation has not only created more land for us and brought huge economic benefits, but also injected new vitality into the development of our country's ports. The ports that were once helpless due to insufficient water depth have now ushered in an excellent opportunity to build deep-water berths.

[0003] Land reclamation is usually carried out by blowing in mud and sand. During the blowing process, a large amount of silt will be blown out. Such sites have the following characteristics: the site is covered with a 1 to 1.5m gravel cushion layer for easy construction, and below the gravel are all blown-in silt soil, silt soil, and soft soil. In addition, the underground is connected to the sea water and the groundwater cannot be effectively drained. Such sites have low foundation bearing capacity and small compression modulus and cannot be used directly. Improving the foundation bearing capacity and compression modulus becomes the key and difficulty in dealing with such sites.

[0004] At present, there are many options for treating silt backfill foundations, including preloading method, crushed stone pile method, high-pressure rotary jet pile method, cement soil mixing method and dynamic compaction replacement method. However, these traditional methods often have some limitations. The preloading method has a long treatment period, low foundation bearing capacity, large deformation in the later stage, and high cost; the crushed stone pile method requires high materials, long construction period, and high cost; the cement soil mixing method and high-pressure rotary jet pile method are expensive and have a long construction period, and will also bring serious environmental pollution problems; and the traditional dynamic compaction replacement method has limited effect on deep saturated soft soil layers because groundwater and shrinkage pores limit the replacement depth. Therefore, the use of traditional foundation treatment methods is difficult to achieve the expected results for treating high-water level silt landfill sites in coastal areas, and the cost is also very high. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for treating silt backfill foundation by dynamic compaction replacement, which has a large replacement depth, a short cycle and a low cost.

[0006] The present invention provides a method for treating sludge backfill foundation by dynamic compaction replacement, comprising the following steps:

[0007] S100. Carry out construction preparation. According to the geological conditions and construction conditions of the site, it is planned to replace 8m thick silt. A crane and rammer that can meet the dynamic compaction replacement depth are equipped. Dynamic compaction replacement materials that meet the requirements are prepared. The site is leveled and filled with 0.5 to 1.0m thick gravel materials. The composition of the gravel materials is the same as that of the dynamic compaction replacement materials, which meets the construction requirements of the construction equipment. The dynamic compaction replacement test includes two spot compactions and two full compactions.

[0008] S200, measure and lay out, mark the first tamping points on site, and arrange the first tamping points in a plum blossom shape;

[0009] S300, excavating a first mud outlet, determining the size of the first mud outlet according to the distance between two adjacent first-pass tamping points, the distance between two adjacent first-pass tamping points being 3 to 4 meters, and excavating the first mud outlet symmetrically with the first-pass tamping point as the center;

[0010] S400, the first spot tamping construction, gradually improving the replacement energy level, and carrying out strong tamping replacement pier construction according to the designed construction parameters. After the first spot tamping construction is completed, the first mud outlet is desilted and backfilled;

[0011] S500, measuring and laying out, marking the second tamping points on site, the second tamping points are arranged in a plum blossom shape, and the second tamping points are staggered with the first tamping points;

[0012] S600, the second spot tamping construction, gradually improve the replacement energy level, carry out strong tamping replacement pier construction according to the designed construction parameters, during the second spot tamping construction, when the site is uplifted, dig the second mud outlet at the position where the uplift exceeds 50cm, and determine the size of the second mud outlet according to the distance between two adjacent second tamping points, the distance between two adjacent second tamping points is 3 to 4m, after the second spot tamping construction is completed, dredge and backfill the second mud outlet;

[0013] S700, after an interval of 7 days, start full tamping construction, with no interval between two full tamping constructions;

[0014] S800, roll 6 times after tamping.

[0015] Optionally, in step S300, a first mud outlet is symmetrically excavated at a position 1.5 to 2.5 m away from the center of the first tamping point, and the dimensions of the first mud outlet are 1 m in length, 1 m in width, and 1.5 m in depth.

[0016] Optionally, step S400 adopts the following method:

[0017] S401, after the tamping machine is in place, start the first round of spot tamping construction, start from the low energy level during construction, fill the filling material while construction, and fill 1 / 3 to 1 / 2 of the tamping pit depth each time. When 2 to 3 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40 cm, the tamping pit is filled;

[0018] S402, improve the replacement energy level, fill the material while constructing, and fill 1 / 3-1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for 3-4 times without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 30 cm, fill the ramming pit completely;

[0019] S403, raising the replacement energy level to the replacement energy level required by the design, filling the material while constructing, and filling 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, the ramming pit is filled and ramming is continued, while filling the material while ramming. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached;

[0020] S404. During the tamping process, the silt in the site is squeezed out along the first mud outlet, and the silt is cleared out of the site using a loader and an excavator. After the first spot tamping construction is completed, all the silt within a depth of 1.5m from the first mud outlet is cleared out of the site and backfilled with gravel.

[0021] Optionally, step S600 adopts the following method:

[0022] S601. After an interval of 7 days, start the second round of spot tamping construction. Start from the low energy level during construction and fill the material while constructing. Each time, fill the material to 1 / 3 to 1 / 2 of the depth of the tamping pit. When 2 to 3 consecutive tampings can be performed without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40 cm, fill the tamping pit.

[0023] S602, improve the replacement energy level, fill the material while constructing, and fill 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When 3 to 4 consecutive rammings can be performed without difficulty in sucking and lifting the hammer, and the settlement is controlled within 30 cm, fill the ramming pit completely;

[0024] S603, increase the replacement energy level to the replacement energy level required by the design, fill the filling material while constructing, and fill the filling material to 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, fill the ramming pit and continue ramming, while filling the filling material. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached;

[0025] S604. During the tamping process, the silt in the site is squeezed out along the second mud outlet, and the silt is cleared out of the site using a loader and an excavator. After the second spot tamping construction is completed, all the silt within a depth of 1.5m from the second mud outlet is cleared out of the site and backfilled with gravel.

[0026] Optionally, in step S700, during full tamping construction, the hammer marks overlap by 1 / 4 of the hammer diameter.

[0027] Optionally, step S800 adopts the following method:

[0028] S801, use a vibratory roller with a vibration force of 40t to vibrate and roll for 6 times;

[0029] S802, the rolling sequence is static rolling 2 times and vibration rolling 4 times;

[0030] S803, when rolling, the wheel marks overlap by 1 / 4.

[0031] Optionally, in step S100, the dynamic compaction replacement material is a well-graded block stone with a particle size of less than 200 mm and a mud content of less than 10%.

[0032] Compared with the prior art, the technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0033] The embodiment of the present invention provides a method for treating a silt backfill foundation by dynamic compaction replacement. By respectively excavating a first mud outlet and a second mud outlet during two-pass spot compaction replacement construction, the silt can be discharged from the first mud outlet and the second mud outlet, thereby reducing the internal pressure of the site. By gradually increasing the replacement energy level, two-pass spot compaction replacement is performed followed by full compaction, thereby improving construction safety, penetrating the silty soil layer, so that the replacement depth reaches 8m, and the delivery depth of the replacement material is increased, so that the soft soil is reinforced and compacted, forming a replacement pier body to increase the integrity of the foundation, thereby improving the bearing capacity and compression modulus of the foundation, and achieving the purpose of foundation treatment. This method has low cost and short cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0036] Figure 1 This is a first-pass replacement tamping point arrangement diagram according to an embodiment of the present invention;

[0037] Figure 2 This is a second replacement tamping point arrangement diagram according to an embodiment of the present invention;

[0038] Figure 3 A site geological map according to an embodiment of the present invention;

[0039] Figure 4 This is a layout diagram of the first pass of silt squeezing in replacement construction according to an embodiment of the present invention;

[0040] Figure 5 This is a layout diagram of the second round of silt removal in the replacement construction described in an embodiment of the present invention.

[0041] Among them, 1. plain fill; 2. blown fill silt soil; 3. first layer of silty clay; 4. second layer of silty clay; 5. first mud outlet; 6. first tamping point; 7. second mud outlet; 8. second tamping point. DETAILED DESCRIPTION

[0042] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0043] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0044] Reference Figures 1 to 5 As shown, this embodiment provides a method for treating sludge backfill foundation by dynamic compaction replacement, comprising the following steps:

[0045] S100. Carry out construction preparation. According to the geological conditions and construction conditions of the site, it is planned to replace 8m thick silt. A crane and rammer that can meet the dynamic compaction replacement depth are equipped. Prepare dynamic compaction replacement materials that meet the requirements. The dynamic compaction replacement materials are selected from well-graded blocks. The block size is required to be less than 200mm and the mud content is less than 10%. The site is leveled and paved with crushed stone materials with a thickness of 0.5 to 1.0m. The crushed stone materials have the same composition as the dynamic compaction replacement materials and meet the construction requirements of the construction equipment. The dynamic compaction replacement test includes two spot compactions and two full compactions;

[0046] S200, measuring and laying out, marking the first tamping point 6 on site, and the first tamping point 6 is arranged in a plum blossom shape;

[0047] S300, excavating the first mud outlet 5, determining the size of the first mud outlet 5 according to the distance between two adjacent first-pass tamping points 6, the distance between two adjacent first-pass tamping points 6 is 3 to 4 m, and symmetrically excavating the first mud outlet 5 with the first-pass tamping point 6 as the center. Specifically, the distance between two adjacent first-pass tamping points 6 is selected according to the load size and the bearing capacity of the original soil, usually 2 to 3 times the diameter of the tamping hammer, and the diameter of the tamping hammer is usually selected to be 1.2 m. The tamping machine legs occupy 1 m around the first-pass tamping point 6, and a 1 m range of tamping machine legs is required between two adjacent first-pass tamping points 6. Considering the safety distance from the tamping machine legs to the first mud outlet 5, the length and width of the first mud outlet 5 can be selected to be 1 to 1.5 m, and the depth is 1.5 m. Preferably, the first mud outlet 5 is symmetrically excavated at a position 1.5 to 2.5 m away from the center of the first-pass tamping point 6, and the dimensions of the first mud outlet 5 are 1 m in length, 1 m in width, and 1.5 m in depth;

[0048] S400, the first spot tamping construction is carried out to gradually increase the replacement energy level, and the strong tamping replacement pier construction is carried out according to the designed construction parameters. After the first spot tamping construction is completed, the first mud outlet 5 is desilted and backfilled;

[0049] S401, after the tamping machine is in place, start the first round of spot tamping construction, start from the low energy level during construction, fill the filling material while construction, and fill 1 / 3 to 1 / 2 of the tamping pit depth each time. When 2 to 3 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40 cm, the tamping pit is filled;

[0050] S402, improve the replacement energy level, fill the material while constructing, and fill 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When 3 to 4 consecutive rammings can be performed without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 30 cm, the ramming pit is filled;

[0051] S403, raising the replacement energy level to the replacement energy level required by the design, filling the material while constructing, and filling 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, the ramming pit is filled and ramming is continued, while filling the material while ramming. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached;

[0052] S404. During the tamping process, the silt in the site is squeezed out along the first mud outlet 5, and the silt is cleared out of the site using a loader and an excavator. After the first spot tamping construction is completed, all the silt within a depth of 1.5m from the first mud outlet 5 is cleared out of the site and backfilled with gravel.

[0053] S500, measuring and laying out, marking the second tamping points 8 on site, the second tamping points 8 are arranged in a plum blossom shape, and the second tamping points 8 are arranged staggered with the first tamping points 6;

[0054] S600, the second spot tamping construction, gradually improve the replacement energy level, and carry out strong tamping replacement pier construction according to the designed construction parameters. During the second spot tamping construction, when the site is uplifted, a second mud outlet 7 is excavated at a position where the uplift exceeds 50cm, and the size of the second mud outlet 7 is determined according to the spacing between two adjacent second tamping points 8. The spacing between two adjacent second tamping points 8 is 3 to 4m. After the second spot tamping construction is completed, the second mud outlet 7 is dredged and backfilled. Specifically, the size of the second mud outlet 7 is 1m long, 1m wide, and 1.5m deep. Of course, the size of the second mud outlet 7 can be appropriately increased without affecting the construction of the adjacent second tamping points 8;

[0055] S601. After an interval of 7 days, start the second round of spot tamping construction. Start from the low energy level during construction and fill the material while constructing. Each time, fill the material to 1 / 3 to 1 / 2 of the depth of the tamping pit. When 2 to 3 consecutive tampings can be performed without suction of the hammer or difficulty in lifting the hammer, and the settlement is controlled within 40 cm, fill the tamping pit.

[0056] S602, improve the replacement energy level, fill the material while constructing, and fill 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When 3 to 4 consecutive rammings can be performed without hammer suction or difficulty in lifting the hammer, and the settlement is controlled within 30 cm, fill the ramming pit completely;

[0057] S603, increase the replacement energy level to the replacement energy level required by the design, fill the material while constructing, and fill 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, fill the ramming pit and continue ramming, while filling the material. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached;

[0058] S604. During the tamping process, the silt in the site will be squeezed out along the second mud outlet 7. The silt will be cleared out of the site using a loader or excavator. After the second tamping construction is completed, all the silt within a depth of 1.5 m from the second mud outlet 7 will be cleared out of the site and backfilled with gravel.

[0059] S700, after an interval of 7 days, start full tamping construction, with no interval between two full tamping constructions, and the hammer marks overlap by 1 / 4 of the hammer diameter;

[0060] S800, roll 6 times after tamping.

[0061] S801, use a vibratory roller with a vibration force of 40t to vibrate and roll for 6 times;

[0062] S802, the rolling sequence is static rolling 2 times and vibration rolling 4 times;

[0063] S803, when rolling, the wheel marks overlap by 1 / 4.

[0064] The arrangement parameters of the first tamping point 6, the second tamping point 8, the first mud outlet 5 and the second mud outlet 7 are as follows:

[0065] Embodiment 1:

[0066] The proposed project is a filling site. The strata show a characteristic of gradually newer from northeast to southwest. The strata are gently inclined and are mainly composed of Upper Proterozoic strata. The filling material is saturated silt and silty soil with a thickness of about 8.0m. The groundwater level varies greatly with the tide.

[0067] After testing, it was found that when dynamic compaction replacement construction was carried out without setting up a mud outlet, the replacement depth was 6 to 7m. By setting up the first mud outlet 5 and the second mud outlet 7 for dynamic compaction replacement construction, the replacement depth reached 7 to 8m, which significantly improved the delivery depth of the replacement material.

[0068] Strata conditions:

[0069] Reference Figure 3 As shown, the replacement zone strata are divided into 4 layers from top to bottom, as follows:

[0070] ① Plain fill Variegated, slightly wet to saturated, slightly dense to medium dense, composed of crushed stone, angular gravel, sand, clay and boulders. The crushed stone particle size is 20 to 150 mm, and the content is 40% to 50%. It contains boulders in some places, with particle size greater than 200 mm and content of 20% to 30%. The layer thickness is 0.3 to 1.5 m.

[0071] ②Dry fill silt soil Grayish yellow to grayish black, mainly composed of clay, sand, etc., in a soft plastic to fluid plastic state. This layer is formed by filling. The layer thickness is 6.2 to 8.1m, with an average thickness of 8.0m. This layer is generally distributed on the east side of the site. The local thickness is relatively large, and soft soil is congested due to backfilling and squeezing.

[0072] ③The first layer of silty clay Gray-black, soft plastic, thin sand layers in some areas, containing shell fragments, and local phase transformation into silt. This layer is 1.3 to 1.2 m thick and is widely distributed in the site.

[0073] ④The second layer of silty clay Gray-brown to yellow-brown, plastic, with thin sand layers in some places, occasional gravel, uneven soil, and local phase change to clay. This layer is 0.3 to 3.40m thick and is widely distributed in the site.

[0074] Design and construction status:

[0075] The entire site treatment area is about 50,000m 2 After reinforcement and tamping, the bearing capacity of the foundation is required to be no less than 150KPa, the foundation compression modulus is greater than 8MPa, and the replacement depth is about 8.0m.

[0076] Construction parameters:

[0077] (1) Excavation of mud outlet

[0078] Reference Figure 1 and Figure 4 As shown, before the first spot tamping construction is carried out, the first mud outlet 5 is symmetrically excavated at a position 1.5m away from the first tamping point 6. The dimensions of the first mud outlet 5 are 1m long, 1m wide and 1.5m deep, and the excavation position of the first mud outlet 5 does not affect the construction of other first tamping points 6. After the first spot tamping construction is completed, all the silt within a depth of 1.5m of the first mud outlet 5 is cleared out of the site and backfilled with gravel.

[0079] Reference Figure 2 and Figure 5As shown, during the second spot tamping construction process, a point with severe uplift is selected as the second mud outlet 7 by observing the site. Specifically, the second mud outlet 7 is excavated at a position where the uplift exceeds 50 cm. The dimensions of the second mud outlet 7 are 1 m in length, 1 m in width, and 1.5 m in depth. After the second spot tamping construction is completed, all the silt within a depth of 1.5 m of the second mud outlet 7 is cleared out of the site and backfilled with gravel.

[0080] (2) Dynamic compaction replacement parameters

[0081] Reference Figure 1 and Figure 2 As shown, the replacement energy levels required for the first and second tamping designs are both 5000 KN.m. The first tamping points 6 and the second tamping points 8 are arranged in a plum blossom shape with a spacing of 3m and a diameter of 0.6m.

[0082] The point tamping construction is carried out in three stages from low energy level to high energy level. After the tamping machine is in place, the low-energy level replacement construction begins, and filling is added during construction. Each time, only 1 / 3 to 1 / 2 of the tamping pit depth is filled. When 2 to 3 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40cm, the tamping pit is filled. At this time, the energy level is increased, and filling is added during construction. Each time, only 1 / 3 to 1 / 2 of the tamping pit depth is filled. When 3 to 4 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 30cm, the tamping pit is filled. At this time, it is increased to the designed energy level, and filling is added during construction. Each time, only 1 / 3 to 1 / 2 of the tamping pit depth is filled. When more than 4 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, the tamping pit is filled and tamping is continued, while tamping and filling. After that, the filling will fill the tamping pit each time, and the number of single-click hits is ≥25 hits and the average settlement of the last two hits is ≤100mm until the hammer stop standard is reached.

[0083] The full tamping is carried out twice with an energy level of 1000 kN·m, 3 blows at each point, and the hammer marks overlap by 1 / 4 of the hammer diameter.

[0084] After tamping, roll it 6 times, and use a vibratory roller with an exciting force of 40t to vibrate and roll it 6 times, with the wheel marks overlapping by 1 / 4 during rolling.

[0085] Dynamic compaction replacement effect detection:

[0086] (1) Ultra-heavy dynamic penetration test

[0087] After the dynamic compaction and replacement treatment, ultra-heavy dynamic probing was used for detection. The detection depth was 8.0m below the tamping surface. The corrected number of blows was between 5.0 and 9.8. The corrected number of blows for each detection hole increased with depth from top to bottom, and the number of dynamic probing blows increased accordingly, indicating that the pier body was relatively uniform after dynamic compaction and replacement, and the replacement depth was ≥8.0m.

[0088] (2) Static load test

[0089] Static load test is used to detect the foundation bearing capacity, and the characteristic value of the foundation bearing capacity is ≥150kPa.

[0090] The above-mentioned strong compaction replacement method for silt backfill foundation treatment is adopted. By excavating the first mud outlet 5 and the second mud outlet 7 respectively during the two replacement constructions, the silt can be discharged from the first mud outlet 5 and the second mud outlet 7, thereby reducing the internal pressure of the site. By gradually increasing the replacement energy level and performing half-pit filling, the construction safety is improved. The half-pit filling can effectively send the replacement material into the underground to form a replacement pier body to increase the integrity of the foundation, thereby improving the bearing capacity of the foundation and achieving the purpose of foundation treatment. Strong compaction replacement strengthens and compacts the soft soil, improves the bearing capacity and compression modulus of the foundation, and the strong compaction replacement pier needs to penetrate the silty soil layer so that the replacement depth reaches 8.0m. This method has low cost and short cycle.

[0091] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0092] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but should conform to the widest scope consistent with the principles and novel features invented herein.

Claims

1. A method for treating sludge backfill foundation by dynamic compaction replacement, characterized in that: The following steps are involved: S100. Carry out construction preparation. According to the geological conditions and construction conditions of the site, it is planned to replace 8m thick silt. A crane and rammer that can meet the dynamic compaction replacement depth are equipped. Dynamic compaction replacement materials that meet the requirements are prepared. The site is leveled and filled with 0.5 to 1.0m thick crushed stone materials. The crushed stone materials have the same composition as the dynamic compaction replacement materials and meet the construction requirements of the construction equipment. The dynamic compaction replacement test includes two spot compactions and two full compactions. S200, measuring and laying out, marking the first tamping points (6) on site, and the first tamping points (6) are arranged in a plum blossom shape; S300, excavating a first mud outlet (5), determining the size of the first mud outlet (5) according to the distance between two adjacent first-pass tamping points (6), the distance between the two adjacent first-pass tamping points (6) being 3 to 4 m, and excavating the first mud outlet (5) symmetrically with the first-pass tamping point (6) as the center; S400, the first spot tamping construction is carried out to gradually increase the replacement energy level, and the strong tamping replacement pier construction is carried out according to the designed construction parameters. After the first spot tamping construction is completed, the first mud outlet (5) is desilted and backfilled; S500, measuring and laying out, marking the second tamping points (8) on site, the second tamping points (8) are arranged in a plum blossom shape, and the second tamping points (8) are arranged staggered with the first tamping points (6); S600, the second spot tamping construction is carried out, the replacement energy level is gradually increased, and the strong tamping replacement pier construction is carried out according to the designed construction parameters. During the second spot tamping construction, when the site is uplifted, a second mud outlet (7) is excavated at a position where the uplift exceeds 50 cm, and the size of the second mud outlet (7) is determined according to the distance between two adjacent second tamping points (8), and the distance between two adjacent second tamping points (8) is 3 to 4 m. After the second spot tamping construction is completed, the second mud outlet (7) is desilted and backfilled; S700, after an interval of 7 days, start full tamping construction, with no interval between two full tamping constructions; S800, roll 6 times after tamping.

2. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: In the step S300, a first mud outlet (5) is symmetrically excavated at a position 1.5 to 2.5 m away from the center of the first tamping point (6), and the dimensions of the first mud outlet (5) are 1 m in length, 1 m in width, and 1.5 m in depth.

3. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: The step S400 adopts the following method: S401, after the tamping machine is in place, start the first round of spot tamping construction, start from the low energy level during construction, fill the filling material while construction, and fill 1 / 3 to 1 / 2 of the tamping pit depth each time. When 2 to 3 consecutive tampings can be made without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40 cm, the tamping pit is filled; S402, improve the replacement energy level, fill the material while constructing, and fill 1 / 3-1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for 3-4 times without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 30 cm, fill the ramming pit completely; S403, raising the replacement energy level to the replacement energy level required by the design, filling the material while constructing, and filling 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, the ramming pit is filled and ramming is continued, while filling the material while ramming. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached; S404. During the tamping process, the silt in the site is squeezed out along the first mud outlet (5), and the silt is cleared out of the site using a loader and an excavator. After the first round of spot tamping is completed, all the silt within a depth of 1.5 m from the first mud outlet (5) is cleared out of the site and backfilled with gravel.

4. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: The step S600 adopts the following method: S601. After an interval of 7 days, start the second round of spot tamping construction. Start from the low energy level during construction and fill the material while constructing. Each time, fill the material to 1 / 3 to 1 / 2 of the depth of the tamping pit. When 2 to 3 consecutive tampings can be performed without difficulty in sucking the hammer or lifting the hammer, and the settlement is controlled within 40 cm, fill the tamping pit. S602, improve the replacement energy level, fill the material while constructing, and fill 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When 3 to 4 consecutive rammings can be performed without difficulty in sucking and lifting the hammer, and the settlement is controlled within 30 cm, fill the ramming pit completely; S603, increase the replacement energy level to the replacement energy level required by the design, fill the filling material while constructing, and fill the filling material to 1 / 3 to 1 / 2 of the depth of the ramming pit each time. When continuous ramming can be performed for more than 4 times without difficulty in sucking the hammer or lifting the hammer, fill the ramming pit and continue ramming, while filling the filling material. Thereafter, the filling material will fill the ramming pit each time until the ramming stop standard is reached; S604. During the tamping process, the silt in the site is squeezed out along the second mud outlet (7), and the silt is cleared out of the site using a loader and an excavator. After the second tamping construction is completed, all the silt within a depth of 1.5 m from the second mud outlet (7) is cleared out of the site and backfilled with gravel.

5. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: In step S700, during full tamping construction, the hammer marks overlap by 1 / 4 of the hammer diameter.

6. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: The step S800 adopts the following method: S801, use a vibratory roller with a vibration force of 40t to vibrate and roll for 6 times; S802, the rolling sequence is static rolling 2 times and vibration rolling 4 times; S803, when rolling, the wheel marks overlap by 1 / 4.

7. The method for treating sludge backfilling foundation by dynamic compaction replacement according to claim 1 is characterized in that: In the step S100, the dynamic compaction replacement material is selected from well-graded blocks of stone, the particle size of the blocks of stone is less than 200 mm, and the mud content is less than 10%.

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