Slope protection method for ship lock large-volume excavation

Abstract

The ship lock large-volume excavation slope protection method comprises the steps that staged excavation is carried out according to the sequence from an upper lock head, a lock chamber to a lower lock head, and foundation pit dewatering construction is synchronously carried out in the excavation process; in the staged excavation, an upper lock head, a lock chamber and a lower lock head are divided into a plurality of sections, each section is divided into a plurality of layers, each section is continuously excavated for multiple times from top to bottom, no less than two layers are excavated each time, in the excavation of the multiple sections, the previous section is excavated each time, the adjacent section is excavated each time, and the like until all the sections are excavated; and support pile foundation construction is further included, specifically, occlusion cast-in-place piles, cement mixing piles and steel sheet piles are included. And in combination with the foundation pit design, the slope stability of each part is calculated by adopting a Sweden splitting method. Meanwhile, for the existing condition that soil is prone to collapse, the cement mixing piles are adopted for reinforcing and improving the geological conditions, and the overall stability of the slope is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of slope protection during excavation, and in particular to a method for protecting the slope of a large-volume excavation of a ship lock. Background Art

[0002] For specific navigational construction, additional vessels are required to accommodate shipping. The lock chamber (with effective dimensions of 306 meters x 25 meters x 4.5 meters and a designed annual one-way cargo throughput capacity of 28.2 million tons) is quite large. During construction, the main deep foundation pit excavation was divided into the upper lock section, the lock chamber section, and the lower lock section. Simultaneously, surveys revealed that structures and facilities within twice the excavation depth surrounding the main lock pit primarily include the first-line ship locks and approach channel, 10kV high-voltage power lines, streetlights, monitoring systems, and stormwater wells. Furthermore, the main lock pit is located adjacent to the first-line ship locks, posing a significant safety risk to these structures and facilities. Furthermore, the deep foundation pit is large, necessitating simultaneous excavation, slope protection, drainage, and monitoring. Furthermore, the main lock pit is 544 meters long, 130.5 meters wide at its widest point (at the upper lock pit), and 10 meters deep. It is mainly divided into three parts: the upper gate foundation pit, the gate chamber foundation pit and the lower gate foundation pit.

[0003] Three bridges were rebuilt, about 670 meters of flood control embankments were demolished and rebuilt, the Xinba River was rerouted (including box culverts) for about 380 meters, and one upstream and downstream remote anchorage was built, as well as corresponding supporting facilities.

[0004] The main lock pit is 544 meters long and 130.5 meters wide at its widest point (at the upper lockhead). It is divided into three sections: the upper lockhead pit, the lock chamber pit, and the lower lockhead pit. The lock pit has a large height difference and is reinforced with cement-mixed piles. Larsen steel sheet piles are used for support and waterstopping at the top of the pit. Summary of the Invention

[0005] The object of the present invention is to provide a method for protecting large-volume excavation slopes of a ship lock to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0007] A method for protecting the slopes of large-volume excavations of ship locks, comprising excavating in stages from the upper lock head, lock chamber to the lower lock head, and simultaneously carrying out foundation pit dewatering during the excavation;

[0008] In the staged excavation, the upper gate, gate chamber and lower gate are divided into several sections, each section is divided into several layers, and each section is excavated continuously from top to bottom for multiple times, with each excavation of no less than two layers. When several sections are excavated, each time the previous section is excavated, the adjacent section is excavated once, and so on, until all the excavation is completed;

[0009] It also includes support pile foundation construction, including interlocking cast-in-place piles, cement mixing piles and steel sheet piles.

[0010] Furthermore, during the foundation pit dewatering construction, the area from the upper gate head, gate chamber to the lower gate head is divided into at least 5 areas, and the foundation pit dewatering in each area works independently.

[0011] Furthermore, each section is divided into several layers, each layer is less than 1m thick, and during multiple continuous excavations, the excavation height each time is not less than 3m.

[0012] Furthermore, the length of each of the several sections is not less than 30m.

[0013] Furthermore, during the construction of the support pile foundation, the lock chamber is divided into several sections. In the downstream section of the lock chamber, the slopes in the 7.7m width range outside the bottom edge of the foundation pit on both sides of the 8th to 20th sections near the upper lock head are reinforced with cement mixing piles. The entire slope of the left side of the lock chamber and the downstream navigation channel of the first-line ship lock of the 14th to 20th sections are reinforced with cement mixing piles; the entire slope of the left bank of the lower lock head and the downstream navigation channel of the first-line ship lock are reinforced with cement mixing piles, and the slope of the right bank is reinforced with cement mixing piles.

[0014] Furthermore, in the 14th to 20th sections, the gate chamber section and the left bank of the lower gate head are supported and reinforced with interlocking cast-in-place piles.

[0015] Furthermore, during the construction of the support pile foundation, the steel sheet piles include the anti-seepage steel sheet piles between the upper lock head and the 1st to 13th section lock chambers and the first line ship lock, and the steel sheet piles for supporting the pouring platform on the upper lock head to the upstream approach channel side, all of which are IV type Larsen steel sheet piles.

[0016] Furthermore, in the foundation pit dewatering, the dewatering wells are distributed within the steel sheet piles.

[0017] Furthermore, it also includes the calculation of the overall stability of the earthwork using the Swedish strip method, specifically including the calculation of the upper gate head, the gate chamber and the lower gate chamber.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. Use Larsen steel sheet piles on top to effectively enhance slope stability;

[0020] 2. The use of interlocking cast-in-place piles and the original lock channel achieves the purpose of supporting and stopping water, while directly ensuring the stability of the bank protection of the original channel.

[0021] 3. The use of cement mixing piles to reinforce the soil has effectively improved the soil quality of the slope and reduced the risk of landslides during rainy seasons. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention provides a flow chart of a method for protecting large-volume excavation slopes of a ship lock. DETAILED DESCRIPTION

[0023] The present invention is described in detail below with reference to the various embodiments shown in the accompanying drawings, but it should be noted that these embodiments are not limitations of the present invention, and any equivalent transformations or substitutions in functions, methods, or structures made by ordinary technicians in this field based on these embodiments are all within the scope of protection of the present invention.

[0024] Refer to the attached Figure 1 As shown, this embodiment is mainly used for a locally confidential project. The ship lock project in this project is located in Hangzhou City, with a total length of approximately 2.49 kilometers. The total planned construction period is 48 months, including 3 months for design and 45 months for construction.

[0025] The construction scale and main engineering contents are as follows: construction of one new Class III ship lock (with an effective chamber size of 306m × 25m × 4.5m and a designed annual one-way cargo throughput capacity of 28.2 million tons), reconstruction of three bridges, demolition and reconstruction of about 670 meters of flood control embankments, rerouting of the Xinba River (including box culverts) of about 380 meters, one upstream and one downstream remote anchorage, and corresponding supporting facilities.

[0026] In this project, the plane size of the upper lock is 32m×58m, the design elevation of the foundation bottom is -6.2m, the current ground elevation is 5.85~7.12m, and the excavation is carried out from about 6.0m of the original ground on the side of the first-line ship lock. The rest of the area will be excavated after the site is leveled to an elevation of 5.0m. The maximum excavation width is 130.5m and the maximum excavation depth is about 12.2m.

[0027] The lower lockhead has plan dimensions of 32m x 58m, with a designed foundation elevation of -5.4m and current ground elevations ranging from 1.90 to 6.82m. The left bank and the downstream approach channel of the first-line ship lock are supported by double rows of interlocking cast-in-place piles. The site elevation is -1.4m, and the entire slope is reinforced with cement-mixed piles at a replacement ratio of 0.47. The right bank slope is also reinforced with cement-mixed piles. The left bank of the lower lockhead was excavated from the original surface, and the right bank was excavated after the site was leveled to an elevation of 5.0m. The maximum excavation width is 98.6m, and the maximum excavation depth is approximately 10.4m.

[0028] The lock chambers are 306m long and 25m wide. The design elevation of the foundation bottom is -5.0m, and the current ground elevation is 4.72 to 6.14m. The slopes on both sides of lock chambers 8# to 20#, covering a width of 7.7m, are reinforced with cement-mixed piles. The left side of lock chambers 14# to 20# and the downstream approach channel of the first-line ship lock are supported by interlocking cast-in-place piles (double rows of cast-in-place piles are used on the left side of lock chambers 19# to 20#). The entire slope is reinforced with cement-mixed piles, with a replacement ratio of 0.3. The left bank of the lock chambers was excavated approximately 6.0m from the original ground level, and the right bank was excavated after the site was leveled to 5.0m. The maximum excavation width is 89.2m, and the maximum excavation depth is approximately 11.0m.

[0029] Concrete pouring construction platforms are set up at the upper gate near the upstream pilot channel side and at the lower gate near the downstream pilot channel side. The upper gate is supported by 12m long steel sheet piles, and the lower gate adopts a 4:1 slope. Anti-seepage steel sheet piles with a length of 15m are driven 1m outside the top edge of the slope on the upper gate and the 1st to 13th section lock chambers near the first-line ship lock.

[0030] In addition to interlocking cast-in-place pile support and cement-mixed pile reinforcement, the remaining slopes of the upper gate, gate chamber, and lower gate are protected with sprayed C20 concrete with a thickness of 60-80 mm. The main lock excavation volume is approximately 336,400 cubic meters. Pipe wells were used to dewater the foundation pit before excavation began. Excavation began only after the water level dropped to 0.5 m below the base.

[0031] The construction in this embodiment is as follows:

[0032] The first step is measurement and layout.

[0033] Before construction, the project team reviews the coordinates and elevations of the control points. After confirmation by the supervising engineer, these serve as the basis for the layout of the control network. The principles for the layout of the control network are safety, stability, reliability, and construction-friendly. GPS, total stations, and levels are used to conduct in-depth measurements of the layout points. Plane coordinates and level elevations are calculated and plotted on a graph. The calculated data is submitted to the supervising engineer for review and re-measurement. Only after verification and confirmation by the supervising engineer can the control network points be used.

[0034] The second step is to cut and drain the foundation pit.

[0035] A drainage ditch is set up about 3.0m away from the slope line at the top of the foundation pit. Before excavating the slope, the drainage ditch at the top of the slope should be excavated and completed as required to prevent surface water from seeping into the soil and causing slope instability (landslide) and affecting construction.

[0036] The third step is foundation pit dewatering construction.

[0037] Dewatering is designed to improve the stability of the slope structure and prevent it from failing. It also reduces the moisture content of the excavated soil, facilitating excavation, transportation, and construction within the foundation pit. Dewatering operations should minimize the impact on other construction activities while ensuring the safety of the foundation pit. This ensures effective dewatering while being economically reasonable, while also improving the efficiency of other construction processes and shortening the overall construction period.

[0038] In actual construction, combined with the foundation pit excavation construction plan, the main foundation pit of the ship lock can be divided into three parts: the upper lock head, the lock chamber, and the lower lock head. At the same time, taking into account the actual excavation process, the three parts are further divided into 5 areas. The independence of each unit is considered when arranging open ditch drainage and light well points, while also taking into account the mutual influence. The dewatering work of each unit is carried out simultaneously with the foundation pit excavation construction.

[0039] First, the arrangement of slope dewatering wells.

[0040] According to the actual situation on site, the slope dewatering wells are evenly distributed along the periphery of the foundation pit excavation. At the same time, the layout points are adjusted according to the actual situation on site to avoid the construction road. The following three areas need to be adjusted according to the actual situation on site:

[0041] (1) The lock chamber section and the left bank of the lower gate head of Sections 14 to 20 are supported and reinforced with interlocking cast-in-place piles, which can basically isolate the recharge of groundwater outside the pit to the pit, so there is no need to set up slope dewatering wells in this area.

[0042] (2) In order not to affect the construction at the junction of the upper and lower gates and the pilot channel, slope dewatering wells will not be arranged on the north and south sides of the foundation pit for the time being. This area will be adjusted later based on the actual situation on site.

[0043] (3) The mutual influence among the first-line ship lock, anti-seepage steel sheet piles and foundation pit dewatering is comprehensively considered in the lock head and the lock chamber section of the 1st to 13th sections. The slope dewatering wells are arranged on the inner side of the steel sheet piles to ensure the dewatering effect while minimizing the impact on the first-line ship lock.

[0044] Secondly, open ditch drainage layout.

[0045] Open ditch drainage arrangement for foundation pit interception and drainage.

[0046] Again, light well point dewatering arrangement.

[0047] When the excavation reaches the bottom of the foundation pit, light well point dewatering is arranged at fixed intervals at the bottom of the foundation pit to prevent water seepage from the bottom of the foundation pit and sudden surges at the bottom of the pit.

[0048] The fourth step is foundation pit excavation.

[0049] (1) Before excavation, anti-seepage steel sheet piles shall be constructed between the upper lock head, the 1st to 13th sections of the lock chamber and the first line of ship lock. A construction access road shall be built in the middle of the lock chamber, leading from the right side of the main construction road to the left side of the lock chamber. During the construction of the interlocking cast-in-place piles and cement mixing piles on the left side of the lower lock head, the construction access road crossing the lock chamber can be used to lead to the main construction road or to lead to the existing road downstream along the right bank of the slope protection embankment of the downstream approach channel of the original first line of ship lock.

[0050] (2) Excavation is carried out from the upper gate head, layer by layer and section by section towards the gate chamber and lower gate head. Before the second section is excavated to an elevation below -3.2m, a construction access road is set along the longitudinal axis in the middle of the foundation pit, running through the upper gate head, gate chamber and lower gate head, and connected to the main construction road upstream and downstream respectively. This channel is sloped and transitioned between the sections in the excavated area, with a slope of no more than 1:7; in addition, an oblique channel is set on the right side of the gate chamber leading to the main construction road. This channel is adjusted downstream synchronously with the excavation of the gate chamber.

[0051] (3) After the second section is excavated to an elevation below -3.2m, the longitudinal construction access road in the foundation pit is interrupted at the upper gate head. Before the entire range of the gate chamber is excavated, the right-hand oblique passage is retained.

[0052] (4) After the entire area of ​​the lock chamber is excavated and before the lower gate is excavated to an elevation below -2.4m, the longitudinal channel in the middle of the foundation pit is kept open in the downstream direction, and a downward sloping foundation pit channel is built on the right side slope of the upstream section of the lock chamber for the later construction of the main structure. The channel slope ratio is about 1:10.

[0053] (5) After the excavation of the lower gate continues, the intermediate construction access road is interrupted at the lower gate. When the excavation of the entire foundation pit is completed, the earthwork is transported downstream to the main construction road.

[0054] The excavation of the foundation pit also includes the construction of the supporting structure pile foundation, as follows:

[0055] First, the left side of lock chambers 14#-20# and the downstream approach channel section of the first-line ship lock are supported by interlocking cast-in-place piles. The left side of lock chambers 19#-20# is supported by double rows of cast-in-place piles. The pile foundation layout plan and cross-section are shown below. The C30 cast-in-place piles have a diameter of 1200mm and an interlocking width of 200mm. Pile lengths were adjusted based on actual conditions during construction, and bored cast-in-place piles were required to penetrate at least 0.5m into the moderately weathered rock.

[0056] Secondly, the slopes within a 7.7m width outside the bottom edge of the foundation pit on both sides of the 8#~20# lock chambers are reinforced with cement mixing piles. The entire slope of the left side of the 14#~20# lock chambers and the downstream navigation channel of the first line ship lock are reinforced with cement mixing piles. The entire slope of the left bank of the lower gate and the downstream navigation channel of the first line ship lock are reinforced with cement mixing piles, and the slope of the right bank is reinforced with cement mixing piles. In this embodiment, due to the intersection with the existing ship lock, considering the support and water retaining functions, a double-row cast-in-place support structure is adopted. The front row (waterside) structure adopts a single row of densely arranged cast-in-place piles with a pile diameter of 1.2m, a spacing of 1m, and a long and short interval arrangement. The rear row is cast-in-place with a spacing of 2m. The silty soil behind the piles is reinforced with cement mixing piles. A cap beam is set on the top of the pile, and a connecting beam is set between the front and rear rows of cap beams. A C30 concrete retaining wall is set at the end of the lower gate support structure, connecting with the original bank protection structure to form a continuous water retaining structure.

[0057] All cement-mixed piles are 700mm diameter, double-ended, and constructed using 42.5(R) ordinary Portland cement with a cement content of 15% and a water-cement ratio of 0.55. The composite foundation must meet a bearing capacity of no less than 170kPa. Pile spacing is based on the pile layout and replacement ratio shown above, while pile length is controlled based on the top and bottom elevations of the reinforced soil layer as shown in the cross-sectional diagram. The layout and length of the cement-mixed piles on the right side of the lower gate are based on the slope to the right of the gate chamber. Due to the significant variation in the geological soil layers within this section, the actual pile length was adjusted based on the specific geological conditions during the injection process.

[0058] Again, it also includes steel sheet pile construction.

[0059] The steel sheet piles include anti-seepage steel sheet piles between the upper gate and the 1#-13# lock chambers and the first-line ship lock, as well as steel sheet piles supporting the casting platform on the upstream approach channel side of the upper gate. All are Type IV Larsen steel sheet piles. The anti-seepage steel sheet piles are driven 1m outside the top edge of the slope, with the pile tops flush with the original ground. The piles are 15m long and the total length of the enclosure is approximately 288m. The steel sheet piles supporting the casting platform are driven along the platform edge near the upper gate, with the pile tops at -3.2m and pile lengths of 12m. The total length of the support is approximately 93.5m.

[0060] Finally, the foundation pit is excavated.

[0061] (1) Excavation segmentation

[0062] The main foundation pit of the ship lock is divided into sections of about 30m along the upper lock head, lock chamber and lower lock head.

[0063] (2) Before excavation of the foundation pit, the excavation boundary line shall be measured and marked, the main construction road and the construction access road within the foundation pit shall be built, and the construction of anti-seepage steel sheet piles between the upper gate, 1#~13# lock chambers and the first line ship lock shall be completed; before excavation of the lower gate and 14#~20# lock chambers, the slope protection of the left first line ship lock shall be broken and cleaned (after the cofferdam construction is completed), and then the interlocking cast-in-place pile support construction and the slope cement mixing pile reinforcement shall be completed.

[0064] (3) First stage excavation

[0065] Excavation of the main foundation pit of the ship lock will begin at the upper gate area and proceed step by step toward lock chambers 1 to 20 and the lower gate. Excavation of each section will be carried out in layers with a thickness of no more than 1m at a time. Excavation will begin with sections 1 and 2. When three layers have been excavated to a bottom elevation of 3.0m, the third section will begin. Once the third section has been excavated layer by layer to a bottom elevation of 3.0m, sections 1 and 2 will continue to be excavated layer by layer to a bottom elevation of -0.2m. Simultaneously, excavation of section 4 will begin. Once the fourth section has been excavated layer by layer to a bottom elevation of 3.0m, section 3 will continue to be excavated layer by layer to a bottom elevation of -0.2m. Then, sections 1 and 2 will continue to be excavated layer by layer to a bottom elevation of -3.2m.

[0066] During the excavation process, the slope shall be cut toward the upstream pilot channel and on both sides according to the designed slope ratio; the height of the construction access road within the excavation range shall be adjusted as the excavation height changes. Since steps with a height difference of about 3m will gradually be formed during the excavation, the slope ratio of the channel position shall always be kept no more than 1:7 during the excavation process to ensure the smooth flow of the channel. The other height difference parts of each level of steps shall be sloped at a transition ratio of about 1:3.

[0067] Earthwork transport vehicles can reach the main construction road through the construction access road in the direction of the upstream navigation channel (transportation direction one), the inclined access road in the lock chamber (transportation direction two) or the construction access road passing through the lock chamber and the lower gate (transportation direction three).

[0068] (4) Second stage excavation

[0069] After the first and second sections were excavated layer by layer to the bottom elevation of -3.2m, supporting steel sheet piles were driven at the casting platform, and the excavation of the fifth section began at the same time. After the fifth section was excavated layer by layer to the bottom elevation of 3.0m, the fourth section was excavated layer by layer to the bottom elevation of -0.2m, and the third section was excavated layer by layer to the bottom elevation of -3.2m. The second section was excavated layer by layer to the bottom elevation of -6.2m, and the continuation of the slope of the second section in the first section was excavated in place according to the slope ratio.

[0070] During the excavation process, the slope is cut toward the upstream pilot channel and on both sides according to the designed slope ratio; the height of the construction access road within the excavation range is adjusted as the excavation height changes, and the slope ratio of the access road is always kept no more than 1:7. After the second section is excavated, the construction access road is interrupted here, and the rest of the area remains unobstructed. The oblique construction access road leading from the lock chamber to the main construction road moves toward the downstream side as the excavation area expands; other height difference parts of each level of steps are sloped at a slope ratio of about 1:3.

[0071] Earth transport vehicles can reach the main construction road through the inclined access road of the lock chamber (transport direction one) or the construction access road passing through the lock chamber and the lower gate head (transport direction two).

[0072] (5) Third stage excavation

[0073] Continue excavation toward the sixth and seventh sections according to the aforementioned excavation principles and sequence, excavating the seventh section layer by layer to an elevation of 3.0m, the sixth section layer by layer to an elevation of -0.2m, the fifth section layer by layer to an elevation of -3.2m, and the third and fourth sections layer by layer to an elevation of -5.0m. Then begin excavation of the eighth section. After the eighth section has been excavated layer by layer to a bottom elevation of 3.0m, continue excavating the seventh section layer by layer to a bottom elevation of -0.2m. Pause excavation for the sixth and fifth sections before beginning excavation of the ninth section. Excavate the sixth, seventh, eighth, and ninth sections in sequence to an elevation of -0.2m (the interlocking cast-in-place pile area of ​​the ninth section will be excavated to -1.0m based on the secondary slope platform elevation). At this elevation, complete the 7.7m slope reinforcement with cement mixing piles on both sides of the 8# to 14# gate chambers.

[0074] After the partial slope of the lock chamber section is formed, a safe passage for people to go up and down is built.

[0075] Earthwork transport vehicles are led to the downstream main construction road via a construction access road that passes through the lock chamber and the lower gate head. The slope ratio of the access road between each section is guaranteed to be no more than 1:7.

[0076] (6) Fourth stage excavation

[0077] After the sixth, seventh, eighth and ninth sections were excavated to an elevation of -0.2m, while cement mixing pile reinforcement construction was being carried out on the slopes on both sides of the 8# to 14# gate chambers, the tenth, eleventh and twelfth sections were excavated to an elevation of -0.2m (the left side was partially excavated to -1.0m according to the elevation of the secondary slope platform) according to the same steps as above, and the thirteenth section was excavated to an elevation of 3.0m. After the cement mixing piles on both sides of the 8#~14# lock chambers are completed and meet the strength requirements, the fifth, sixth, seventh and eighth sections will be excavated to the elevation of -5.0m, and the ninth section will be excavated to the elevation of -3.2m in the order of "sixth section excavated to the elevation of -3.2m → fifth section excavated to the elevation of -5.0m → seventh section excavated to the elevation of -3.2m → sixth section excavated to the elevation of -5.0m →… → eighth section excavated to the elevation of -5.0m". After the tenth, eleventh and twelfth sections are excavated to the elevation of -0.2m, the cement mixing pile reinforcement construction of the slope within 7.7m on both sides of the 9#~20# lock chambers will be completed.

[0078] (7) Fifth stage excavation

[0079] After the tenth, eleventh, and twelfth sections were excavated to an elevation of -0.2m, the fourteenth section began excavation simultaneously with the cement mixing pile reinforcement work on the slopes of both sides of the 9#-20# lock chambers. The fourteenth section was first excavated layer by layer to an elevation of 3.0m, followed by the thirteenth section, which was then excavated layer by layer to an elevation of -0.2m. After the cement mixing piles on both sides of the 9#-20# lock chambers were completed and met the strength requirements, excavation was continued section by section in the following order: "Section ten, layer by layer excavation to an elevation of -3.2m → Section nine, layer by layer excavation to an elevation of -5.0m → Section eleven, layer by layer excavation to an elevation of -3.2m → Section ten, layer by layer excavation to an elevation of -5.0m → Section twelfth, layer by layer excavation to an elevation of -3.2m → Section eleven, layer by layer excavation to an elevation of -5.0m." After the thirteenth section was excavated layer by layer to an elevation of -0.2m, cement mixing pile reinforcement work on the left side of the lower gate head was completed.

[0080] (8) Sixth stage excavation

[0081] After the excavation of the above sections and the reinforcement of cement mixing piles are completed, the fourteenth section will be excavated in layers to an elevation of -0.2m, and then the thirteenth section will be excavated in layers to an elevation of -2.4m (a slope for the construction access road will be reserved between the fourteenth section), and then the twelfth section will be excavated to an elevation of -5.0m (a slope will be reserved at the construction access road to ensure that the access road is unobstructed, and the thirteenth section will be excavated together when it reaches this elevation).

[0082] Earthwork transport vehicles go from the construction access road at the lower gate head to the downstream main construction road, and the slope ratio of the access road between each section is guaranteed to be no more than 1:7.

[0083] (9) Final excavation

[0084] The excavation of the fourteenth section was continued in layers to an elevation of -1.8m, and then the thirteenth section was excavated in layers to an elevation of -5.4m, completing the excavation of the entire foundation pit. Since the construction access road would be interrupted at this point after the continued excavation of the thirteenth section, the excavation of this section was carried out in a gradual, layer-by-layer, slope-contracting manner from all sides toward the construction access road, ultimately exiting from the downstream side of the construction access road. Earthwork transport vehicles then accessed the main construction road via the downstream approach channel construction access road.

[0085] Step 5: Protection of foundation pit slope.

[0086] The slopes of this project are constructed using large excavations. Based on the soil conditions of the excavated slopes, after the slopes are formed, the sandy soil areas are promptly sprayed with C20 plain concrete for protection. In the clay soil areas, three-dimensional vegetation nets are laid and grass seeds are sown. Temporary green net covering protection measures are adopted for the unformed slopes.

[0087] Step 6: Calculation of foundation pit slope stability.

[0088] The stability of the foundation pit slopes was calculated using Beijing Lizheng Deep Foundation Pit Calculation Software Version 7.0. The slopes on the left side of the 14-20 lock chambers and the left side of the lower gate were reinforced with mixing piles and double-row interlocking piles. These slopes met the stability requirements and are not further detailed. The focus is on calculating the stability of the remaining slopes.

[0089] First, calculate the upper gate head.

[0090] The upper lock head is close to the upstream navigation channel

[0091] 1. Foundation pit excavation cross-section

[0092] The slope of the upper gate near the upstream navigation channel adopts first-level slope reduction + steel sheet pile support, with the top elevation of 5.0m, the base elevation of -6.2m, the foundation pit depth of 11.2m, and a working platform with a width of 8.0m set at the elevation of -3.2m. 12mPU400*170mm steel sheet piles are driven inside the foundation pit, and the steel sheet piles are inserted 9.0m into the base. The slope ratio is 1:10, and it also serves as a construction access road. The working platform is mainly responsible for pouring concrete for the upper gate structure. During pouring, the vehicle is 2.0m away from the edge of the foundation pit, and the top of the slope is 3.0m away from the construction road.

[0093] 2. Basic information of foundation pit excavation is shown in Table 1:

[0094] Table 1:

[0095] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Internal force calculation method Incremental method Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 11.200 Embedment depth (m) 9.000 Pile top elevation (m) -3.200 Pile material type Steel sheet piles <![CDATA[├Cross-sectional area A per meter (cm 2 )]]> 236.00 <![CDATA[├Moment of inertia I per meter (cm 4 )]]> 39600.00 <![CDATA[└Flexural modulus per meter length W (cm 3 )]]> 2200.00 <![CDATA[└Flexural strength f (N / mm 2 )]]> 215 With or without crown beam none Grading levels 1 Overload number 2 Horizontal concentrated forces on the supporting structure 0

[0096] 3. The excavation slope information of foundation pit is shown in Table 2:

[0097] Table 2:

[0098] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 8.000 8.200 10.000

[0099] 4. Groundwater level

[0100] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -0.7m.

[0101] 5. Load conditions

[0102] Here, a construction road runs along the slope to the top, and concrete is being poured on the working platform. The slope stability calculation primarily considers overloading of the top and working platform. When the excavation reaches the base, the pit depth is maximum and the slope stability is at its lowest. The slope stability calculation here considers various load conditions that may exist on the construction access road at the top and the working platform below after the excavation reaches the base.

[0103] Combined with the on-site construction conditions, the load conditions are shown in Table 3 below:

[0104] Table 3:

[0105]

[0106] In summary, in the most unfavorable case, the equivalent load at the slope top is 9.4 kPa, and 10 kPa is taken in the calculation. The equivalent load of the working platform is 11.1 kPa, and 12 kPa is taken in the calculation.

[0107] [Section checking calculation]

[0108] Checking calculation of the bending resistance inside the foundation pit (without considering axial force)

[0109] [[ID=十七]]σnei = M / W

[0110] = 4.458 / (2200.000 * 10 -6 )

[0111] = 2026.428 (kPa)

[0112] = 2.026 (MPa) < f = 215.000 (MPa), meeting the requirement. Checking calculation of the bending resistance outside the foundation pit (without considering axial force)

[0113] σwai = M / W

[0114] = 126.984 / (2200.000 * 10 -6 )

[0115] = 57719.929 (kPa)

[0116] = 57.720 (MPa) < f = 215.000 (MPa), meeting the requirement. Calculation method: Swedish slip circle method

[0117] Stress state: Total stress method [[ID=四十七]]

[0118] Width of soil strip in the slip circle method: 1.00 m

[0119] Slip surface data

[0120] Overall stability safety factor K s = 3.116

[0121] Radius of the circular arc (m) R = 65.995

[0122] X coordinate of the center of the circle (m) X = 34.224

[0123] Y coordinate of the center of the circle (m) Y = 45.835

[0124] [Checking calculation of anti-overturning stability]

[0125] Anti-overturning safety factor:

[0126] M p ——The passive earth pressure and support force on the anti-overturning bending moment of the pile bottom, and the internal support support force from the internal support pressure

[0127] Decision: For anchor rods or anchor cables, the fulcrum force is the smaller value of the anchoring force and the tensile strength of the anchor rod or anchor cable.

[0128] M a ——Overturning bending moment caused by active earth pressure on pile bottom.

[0129] On the right side of the upper gate (on the main construction road side)

[0130] 1. Foundation pit excavation cross-section

[0131] The slope on the right side of the upper gate (on the side of the main construction road) adopts secondary slope support, with the top elevation of 5.0m, the base elevation of -6.2m, the foundation pit depth of 11.2m, the secondary platform elevation of -0.2m, the platform width of 2.0m, the first-level slope ratio of 1:2.5, and the second-level slope ratio of 1:3; there is no vehicle load on the second-level platform, and the top of the slope is 3.0m away from the main construction road.

[0132] 2. Basic information of foundation pit excavation is shown in Table 4:

[0133] Table 4

[0134] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 11.200 Grading levels 2 Overload number 1

[0135] 3. Excavation slope information of foundation pit is shown in Table 5

[0136] Table 5

[0137] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 5.200 2.500 2 0.000 6.000 3.000

[0138] 4. Foundation pit excavation soil parameters

[0139] Load Cases

[0140] The slope top here has a main construction road, so the slope stability calculation primarily considers the overload condition at the top. When the foundation pit is excavated to the base, the pit depth is maximum and the slope stability is at its worst. The slope stability calculation here is based on various load conditions that may exist on the main construction road at the top of the slope after the foundation pit is excavated to the base. Based on the on-site construction conditions, the load conditions are shown in Table 6:

[0141] Table 6:

[0142]

[0143] In summary, the equivalent load in the most unfavorable case is 9.8kPa, and 10kPa is taken in the calculation.

[0144] The calculation results of natural slope are shown in Table 7:

[0145] Table 7:

[0146]

[0147] Overall stability safety factor K s =1.469>1.35, meeting the specification requirements.

[0148] Left side of the upper lock head (near the first-line ship lock)

[0149] 1. Foundation pit excavation cross-section

[0150] The slope on the left side of the upper lock head (close to the first-line ship lock side) adopts secondary slope support, with the slope top elevation of 6.0m, the base elevation of -6.2m, the foundation pit depth of 12.2m, the secondary platform elevation of -0.2m, the platform width of 2.0m, the first-level slope ratio of 1:2.5, and the second-level slope ratio of 1:3; the slope top is about 10m away from the outer edge of the first-line ship lock structure, and there is no vehicle load on the slope top and the secondary platform.

[0151] 2. Basic information of foundation pit excavation is shown in Table 8.

[0152] Table 8:

[0153] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 12.200 Grading levels 2 Overload number 0

[0154] 3. The excavation slope information of foundation pit is shown in Table 9.

[0155] Table 9:

[0156] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 6.200 2.500 2 0.000 6.000 3.000

[0157] 4. Foundation pit excavation soil parameters

[0158] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -0.7m.

[0159] Natural slope calculation conditions:

[0160] Calculation method: Swedish strip method

[0161] Stress State: Total Stress Method

[0162] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0163] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0164] Soil strip width in strip method: 1.00m

[0165] The calculation results of natural slope are shown in Table 10:

[0166] Table 10:

[0167]

[0168] Overall stability safety factor K s =1.432>1.35, meeting the specification requirements.

[0169] Secondly, the lock chamber

[0170] First, the unreinforced area on the left side of the lock chamber (near the first-line ship lock side)

[0171] 1. Foundation pit excavation

[0172] The slope on the left side of the lock chamber (close to the first-line ship lock) adopts secondary slope support, with the slope top elevation of 6.0m, the base elevation of -5.0m, the foundation pit depth of 11.0m, the secondary platform elevation of -0.2m, the platform width of 2.0m, the first-level slope ratio of 1:2, and the second-level slope ratio of 1:2.5; there is no vehicle load on the slope top and the secondary platform.

[0173] 2. Basic information of foundation pit excavation is shown in Table 11

[0174] Table 11:

[0175] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 11.000 Grading levels 2 Overload number 0

[0176] 3. The excavation slope information of the foundation pit is shown in Table 12:

[0177] Table 12:

[0178] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 6.200 2.000 2 0.000 4.800 2.500

[0179] 4. Foundation pit excavation soil parameters

[0180] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -2.2m.

[0181] Natural slope calculation conditions:

[0182] Calculation method: Swedish strip method

[0183] Stress State: Total Stress Method

[0184] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0185] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0186] Soil strip width in strip method: 1.00m

[0187] Natural slope calculation results table 13:

[0188]

[0189] Overall stability safety factor K s =1.389>1.35, meeting the specification requirements.

[0190] Second, the reinforcement area on the left side of the lock chamber (near the first-line ship lock side)

[0191] 1. Foundation pit excavation

[0192] The slope on the left side of the lock chamber (near the first-line ship lock) is supported by a secondary slope. The slope's top elevation is 6.0m, the base elevation is -5.0m, the foundation pit depth is 11.0m, the secondary platform elevation is -0.2m, and the platform width is 2.0m. The primary slope ratio is 1:2, and the secondary slope ratio is 1:2.5. There is no vehicle load on the top or secondary platform. Due to the thick silt soil in this area, cement mixing piles are used for reinforcement within 7.7m from the bottom of the slope.

[0193] The soil cohesion and internal friction angle of the reinforced area need to be determined based on the area replacement rate.

[0194] c0=mc p +(1-m)c s

[0195]

[0196] Where m is the area replacement rate, which is set to 0.3 according to the drawing requirements;

[0197] c0, c p 、c s are the cohesion (kPa) of the reinforced area, original soil and mixing pile respectively, where c p 、c s They are 13.5kPa and 300kPa respectively;

[0198] are the internal friction angles (°) of the reinforced area, original soil, and mixing pile, respectively. 9.6° and 35° respectively;

[0199] Therefore, the calculated cohesion of the soil in the reinforced area is 214.05 kPa and the internal friction angle is 28.4°.

[0200] Basic information table of foundation pit excavation 14

[0201] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 11.000 Grading levels 2 Overload number 0

[0202] The excavation slope information of the foundation pit is shown in Table 15:

[0203] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 6.200 2.000 2 0.000 4.800 2.500

[0204] Foundation pit excavation soil parameters

[0205] Groundwater level

[0206] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -2.2m.

[0207] Natural slope calculation conditions:

[0208] Calculation method: Swedish strip method

[0209] Stress State: Total Stress Method

[0210] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0211] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0212] Soil strip width in strip method: 1.00m

[0213] Natural slope calculation results table 16:

[0214]

[0215] Overall stability safety factor K s =1.369>1.35, meeting the specification requirements.

[0216] Unreinforced area on the right side of the gate chamber (on the main construction road side)

[0217] 1. Foundation pit excavation

[0218] The slope on the right side of the gate chamber (on the side of the main construction road) adopts secondary slope support, with the top elevation of 5.0m, the base elevation of -5.0m, the foundation pit depth of 10.0m, the secondary platform elevation of -0.2m, the platform width of 6.0m, the first-level slope ratio of 1:2, and the second-level slope ratio of 1:2.5; the second-level platform driveway is 4m wide, 1m away from the slope, and the top of the slope is 3.0m away from the main construction road.

[0219] Basic information of foundation pit excavation is shown in Table 17:

[0220] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 10.000 Grading levels 2 Overload number 2

[0221] The excavation slope information of the foundation pit is shown in Table 18:

[0222] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 6.200 2.000 2 0.000 4.800 2.500

[0223] Groundwater level

[0224] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -2.2m.

[0225] Load Cases

[0226] The slope top here has a main construction road, and the secondary slope platform serves as a construction platform. The slope stability calculation primarily considers overload conditions on the top and secondary platform. When the foundation pit is excavated to the base, the pit depth is maximum and the slope stability is at its lowest. The slope stability calculation is based on various load conditions that may exist on the main construction road and secondary slope platform at the top of the slope after the foundation pit is excavated to the base. Based on the on-site construction conditions, the load conditions are as follows (Table 19):

[0227]

[0228] In summary, under the most unfavorable conditions, the equivalent load on the top of the slope is 9.4 kPa, which is taken as 10 kPa in the calculation; the equivalent load on the working platform is 23.3 kPa, which is taken as 24 kPa in the calculation.

[0229] Natural slope calculation conditions:

[0230] Calculation method: Swedish strip method

[0231] Stress State: Total Stress Method

[0232] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0233] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0234] Soil strip width in strip method: 1.00m

[0235] The calculation results of natural slope are shown in Table 20:

[0236]

[0237]

[0238] Overall stability safety factor K s =1.599>1.35, meeting the specification requirements.

[0239] Reinforced area on the right side of the gate chamber (on the main construction road side)

[0240] 1. Foundation pit excavation

[0241] The slope to the right of the gate chamber (on the main construction road) is supported by a secondary slope. The slope's top elevation is 5.0m, the base elevation is -5.0m, the foundation pit depth is 10.0m, the secondary platform elevation is -0.2m, and the platform width is 6.0m. The primary slope ratio is 1:2, and the secondary slope ratio is 1:2.5. The secondary platform's driveway is 4m wide, 1m from the slope, and 3.0m from the main construction road. Due to the thickness of the silt soil at this location, cement mixing piles were used to reinforce the area within 7.7m from the bottom of the slope.

[0242] The soil cohesion and internal friction angle of the reinforced area need to be determined based on the area replacement rate.

[0243] c0=mc p +(1-m)c s

[0244]

[0245] Where m is the area replacement rate, which is set to 0.3 according to the drawing requirements;

[0246] c0, c p 、c s are the cohesion (kPa) of the reinforced area, original soil and mixing pile respectively, where c p 、c s They are 13.5kPa and 300kPa respectively;

[0247] are the internal friction angles (°) of the reinforced area, original soil, and mixing pile, respectively. 9.6° and 35° respectively;

[0248] Therefore, the calculated cohesion of the soil in the reinforced area is 214.05 kPa and the internal friction angle is 28.4°.

[0249] 3. Basic information of foundation pit excavation is shown in Table 21:

[0250] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 10.000 Grading levels 2 Overload number 2

[0251] 3. The excavation slope information of the foundation pit is shown in Table 22:

[0252] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 6.000 5.200 2.000 2 0.000 4.800 2.500

[0253] 4. Groundwater level

[0254] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -2.2m.

[0255] 5. Load conditions

[0256] The slope top here has a main construction road, and the secondary slope platform serves as a construction platform. The slope stability calculation primarily considers overload conditions on the top and secondary platform. When the foundation pit is excavated to the base, the pit depth is maximum and the slope stability is at its lowest. The slope stability calculation is based on various load conditions that may exist on the main construction road and secondary slope platform after the foundation pit is excavated to the base. Based on the on-site construction conditions, the load conditions are as follows (Table 23):

[0257] Table 23:

[0258]

[0259] In summary, under the most unfavorable conditions, the equivalent load on the top of the slope is 9.4 kPa, which is taken as 10 kPa in the calculation; the equivalent load on the working platform is 23.3 kPa, which is taken as 24 kPa in the calculation.

[0260] Natural slope calculation conditions:

[0261] Calculation method: Swedish strip method

[0262] Stress State: Total Stress Method

[0263] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0264] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0265] Soil strip width in strip method: 1.00m

[0266] The calculation results of natural slope are shown in Table 24:

[0267]

[0268]

[0269] Overall stability safety factor K s =1.527>1.35, meeting the specification requirements.

[0270] Again, the gate

[0271] The lower gate is close to the downstream pilot channel.

[0272] 1. Foundation pit excavation

[0273] The slope of the lower gate near the downstream navigation channel adopts secondary slope support, with the top elevation of 5.0m, the base elevation of -5.4m, the depth of the foundation pit of 10.4m, and a working platform at the elevation of -1.8m. The platform width is 8.0m, the first-level slope ratio is 1:10, and it also serves as a construction access road. The second-level slope ratio is 4:1. The working platform is mainly responsible for pouring concrete for the lower gate structure. During pouring, the vehicle is 2.0m away from the edge of the foundation pit, and the top of the slope is 3.0m away from the construction road.

[0274] Basic information of foundation pit excavation is shown in Table 25:

[0275] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 10.400 Grading levels 2 Overload number 2

[0276] The excavation slope information of the foundation pit is shown in Table 26:

[0277] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 8.000 6.800 10.000 2 0.000 3.600 0.250

[0278] 2. Groundwater level

[0279] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -0.7m.

[0280] 3. Load conditions

[0281] Here, a construction road runs along the slope to the top, and concrete is being poured on the working platform. The slope stability calculation primarily considers overloading of the top and working platform. When the excavation reaches the base, the pit depth is maximum and the slope stability is at its lowest. The slope stability calculation here considers various load conditions that may exist on the construction access road at the top and the working platform below after the excavation reaches the base.

[0282] Combined with the on-site construction conditions, the load conditions are shown in Table 27:

[0283]

[0284] In summary, under the most unfavorable conditions, the equivalent load on the top of the slope is 9.4 kPa, which is taken as 10 kPa in the calculation; the equivalent load on the working platform is 11.1 kPa, which is taken as 12 kPa in the calculation.

[0285] Natural slope calculation conditions:

[0286] Calculation method: Swedish strip method

[0287] Stress State: Total Stress Method

[0288] Cut-off calculation depth below the bottom of the foundation pit: 0.00m

[0289] Search step length for sliding crack surface below the bottom of foundation pit: 5.00m

[0290] Soil strip width in strip method: 1.00m

[0291] The calculation results of natural slope are shown in Table 28:

[0292]

[0293] Overall stability safety factor K s =1.486>1.35, meeting the specification requirements.

[0294] Right side of the lower gate (on the side of the main construction road)

[0295] 1. Foundation pit excavation

[0296] The slope on the right side of the lower gate (on the side of the main construction road) adopts secondary slope support, with the top elevation of 5.0m, the base elevation of -5.4m, the foundation pit depth of 10.4m, the secondary platform elevation of -0.2m, the platform width of 2.0m, the first-level slope ratio of 1:2.5, and the second-level slope ratio of 1:3; there is no vehicle load on the second-level platform, and the top of the slope is 3.0m away from the main construction road.

[0297] 2. Basic information of foundation pit excavation is shown in Table 29:

[0298] Standards and Regulations Technical Specification for Building Foundation Pit Support JGJ 120-2012 Foundation pit grade Level 1 Importance coefficient of foundation pit side wall γ0 1.00 Foundation pit depth H(m) 10.400 Grading levels 2 Overload number 1

[0299] 3. The excavation slope information of the foundation pit is shown in Table 30;

[0300] Slope No. Platform width (m) Slope height (m) Slope coefficient 1 2.000 5.200 2.500 2 0.000 5.200 3.000

[0301] 4. Groundwater level

[0302] According to the precipitation situation, the excavation of the foundation pit ensures that the water level is 0.5m below the base. Combined with the actual construction situation, the base elevation of the upper gate is -6.2m, so the groundwater level of the entire foundation pit base is calculated to be -6.7m. Referring to the precipitation funnel and infiltration line, the equivalent groundwater level at the top of the slope can be taken as -0.7m.

[0303] 5. Load conditions

[0304] The main construction road at the top of this slope is located here, so the slope stability calculation primarily considers the overload condition at the top. When the foundation pit is excavated to the base, the pit depth is maximum and the slope stability is at its worst. The slope stability calculation here is based on various load conditions that may exist on the main construction road at the top of the slope after the foundation pit is excavated to the base. Based on the on-site construction conditions, the load conditions are shown in Table 31:

[0305]

[0306] In summary, the equivalent load in the most unfavorable case is 9.8kPa, and 10kPa is taken in the calculation.

[0307] Overall stability safety factor K s =1.401>1.35, meeting the specification requirements.

[0308] The detailed survey report indicates that the slope's strata vary significantly, with the thickness of the silty soil ranging from 3m to 9m. This stratum is gray, plastic, and has a smooth, slightly lustrous cross-section. It contains small amounts of organic matter and humus, high dry strength, moderate toughness, and no shaking response, resulting in poor slope stability. Calculations indicate that when the silty soil thickness exceeds 5m, the overall slope stability safety factor does not meet requirements, requiring stratum reinforcement. When the silty soil thickness is 5m or less, the overall slope stability safety factor meets requirements.

[0309] The series of detailed descriptions listed above are only specific descriptions of feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. Any equivalent implementation methods or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

[0310] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be included therein. Any reference sign in a claim should not be construed as limiting the claim to which it relates.

[0311] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for protecting large-volume excavation slopes of ship locks, characterized in that: This includes excavating the gate in stages, starting from the upper gate, through the gate chamber, and ending at the lower gate, and simultaneously carrying out foundation pit dewatering during the excavation. In the staged excavation, the upper gate, gate chamber and lower gate are divided into several sections, each section is divided into several layers, and each section is excavated continuously from top to bottom for multiple times, with each excavation of no less than two layers. When several sections are excavated, each time the previous section is excavated, the adjacent section is excavated once, and so on, until all the excavation is completed; It also includes support pile foundation construction, including interlocking cast-in-place piles, cement mixing piles and steel sheet piles.

2. A method for protecting large-volume excavation slopes of ship lock according to claim 1, characterized in that: During the foundation pit dewatering construction, the area from the upper gate head, gate chamber to the lower gate head is divided into at least 5 areas, and the foundation pit dewatering in each area works independently.

3. A method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: Each section is divided into several layers, each layer is less than 1m thick, and during multiple continuous excavations, the excavation height each time is not less than 3m.

4. A method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: Among the several sections, the length of each section is not less than 30m.

5. The method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: During the construction of the support pile foundation, interlocking cast-in-place piles are used to support the left side of the lock chamber near the lower lock head and the downstream approach channel section of the first-line ship lock, and double rows of cast-in-place piles are used to support the left side of the lock chamber near the end of the lower lock head.

6. A method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: During the construction of the support pile foundation, the lock chamber is divided into several sections. In the downstream section of the lock chamber, the slopes in the range of 7.7m width outside the bottom edge of the foundation pit on both sides of the 8th to 20th sections near the upper lock head are reinforced with cement mixing piles. The entire slope of the left side of the lock chamber and the downstream navigation channel of the first-line ship lock of the 14th to 20th sections are reinforced with cement mixing piles; the entire slope of the left bank of the lower lock head and the downstream navigation channel of the first-line ship lock are reinforced with cement mixing piles, and the slope of the right bank is reinforced with cement mixing piles.

7. A method for protecting large-volume excavation slopes of a ship lock according to claim 6, characterized in that: In the 14th to 20th sections, the gate chamber section and the left bank of the lower gate head are supported and reinforced with interlocking cast-in-place piles.

8. The method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: During the construction of the support pile foundation, the steel sheet piles include the anti-seepage steel sheet piles between the upper lock head and the 1st to 13th section lock chambers and the first-line ship lock, and the steel sheet piles for supporting the casting platform on the upstream navigation channel side from the upper lock head, all of which are IV type Larsen steel sheet piles.

9. A method for protecting large-volume excavation slopes of a ship lock according to claim 8, characterized in that: In the foundation pit dewatering, the dewatering wells are distributed in the steel sheet piles.

10. A method for protecting large-volume excavation slopes of a ship lock according to claim 1, characterized in that: It also includes the calculation of the overall stability of the earthwork using the Swedish strip method, specifically including the calculation of the upper gate, the gate chamber and the lower gate chamber.

Images