CN106320368A - A construction method suitable for open-cut pipelines in composite strata - Google Patents

Abstract

The invention relates to the field of building construction, in particular to a construction method suitable for an open cut pipeline of a composite stratum, which comprises the following steps: measuring paying off, replacing and filling the mixture in the excavation lines at two sides of the excavation groove, digging a slope on the upper soil layer, digging a slope on the lower rock layer, replacing and filling the sand and stone at the bottom of the foundation pit of the excavation groove, installing a pipeline and backfilling medium and coarse sand and earthwork; the invention adopts a construction method of the 'hidden cofferdam', the bad soil layers on the upper parts of the two sides of the groove are filled with the mixture of cement and plain soil which are mixed in advance, the hidden cofferdam is formed by layering and compacting to achieve the water stopping effect, the side slope is hung with a net and anchored in the excavation process of the groove, the rock layer on the lower part is broken by a breaking hammer, the construction process is simple, the construction difficulty is low, the requirement of mechanical equipment is less, the construction period is shortened, the construction cost is saved, and the method is safe and effective.

Description

A construction method suitable for open-cut pipelines in composite strata

technical field

The invention relates to the field of building construction, in particular to a method for constructing open-cut pipelines in deep foundation pits under the conditions of water-rich and rock-soil composite strata.

Background technique

Since the reform and opening up, the rapid development of my country's political, economic, and cultural undertakings has brought about a climax of urban construction. In the process of urban drainage and rainwater treatment, the construction of underground pipes and pipe galleries has become a major development trend. For this reason, the construction of open-cut pipelines in deep foundation pits under complex geological conditions has become increasingly frequent. How to ensure trench support and water stop during the construction of open excavation pipelines in deep foundation pits under water-rich and rock-soil complex geological conditions has become an important and difficult point. Larsen steel sheet pile support structure is often used at present. The following is a brief description of the shortcomings of the Larsen steel sheet pile support structure:

The Larsen steel sheet pile support is to install the Larsen steel sheet pile first, and the ratio of the depth of the steel sheet pile to the trench depth should not be less than 1:1. After the excavation is completed, the steel purlin will be installed when the earthwork is excavated to the designed steel purlin position. , Steel support, weld the two ends of the steel support with the steel purlins firmly to achieve the effect of supporting horizontal loads and stopping water. However, when the upper part of the trench is a bad soil layer with a large amount of water, the lower part is a weakly weathered rock layer Under complex geological conditions, Larsen steel sheet piles cannot enter the rock, and after installing steel purlins and steel supports, the lower rock formations cannot be removed by machinery, and can only be removed manually. Poor construction results in long construction period and high time cost, which directly affects economic benefits.

Contents of the invention

In view of the above-mentioned problems, the technical problem to be solved by the present invention is to use the "hidden cofferdam" method to stop water, and to provide a deep foundation pit open-cut pipeline construction method suitable for water-rich and rock-soil composite stratum conditions.

To achieve the above object, the present invention adopts technical scheme as follows:

A construction method suitable for open-cut pipelines in composite strata, comprising the following steps:

1) Measurement and setting out: According to the well position of the inspection well on the construction site and the depth of the excavation trench, measure and release the 2-meter-wide excavation line of the snail layer and liquefied soil layer on both sides of the excavation trench;

2) Replacement of the mixture in the excavation line on both sides of the excavation trench: according to the excavation line from top to bottom, first excavate the upper soil layer in the excavation line, and then remove the lower snail layer 1. Excavation of the liquefied soil layer; when the snail layer and the liquefied soil layer have been excavated, backfill and compact the mixture of cement and plain soil prepared by mixing in advance, and the thickness of each layer of paving is 500-800 mm. After layer paving is completed, an excavator is used for rolling, and then a vibratory tamp is used for compaction. The number of times for each layer of rolling and compaction is greater than or equal to 3-5 times; the mass ratio of cement in the mixture to the wet mass of plain soil 10% to 15%;

3) Slope excavation of the upper soil layer: the upper soil layer in the excavation trench is excavated according to the slope of 1:0.5, and the slope of the upper soil layer is treated with hanging net spraying concrete after excavation;

4) Slope excavation of the lower rock layer: When excavating the upper soil layer in the trench to the Fenghua rock and limestone layer, leave a step with a width of 1 meter on both sides of the trench, and then use a breaker to break the rock layer below the step. Grading and excavation according to the slope of 1:0.5;

5) Replacement of sand and gravel at the bottom of excavated trench foundation pit: After the excavation of the rock layer is completed, replace and level the bottom of the foundation pit with sand and gravel to the preset elevation of the bottom of the pipeline;

6) Pipeline installation;

7) Medium-coarse sand and earthwork backfill.

Specifically, the excavation line is sprinkled with gray and white powder.

Specifically, in the step 2) and step 3), the 20-meter-long excavation trench is used as a section, and excavated in sections.

Concretely, in the above step 3), the treatment steps of hanging net sprayed concrete are as follows: Wedging a number of 10 mm diameter and 40 cm long insert bars vertically on the slope surface, the vertical and horizontal spacing of the insert bars is 1 meter, and laying on each insert bar A layer of Φ1*40*40 steel wire mesh can be sprayed concrete after hanging the mesh. The concrete is fine stone concrete with a strength of C20, and the thickness of the concrete sprayed is 100 mm.

Specifically, the step 6) is carried out according to the following steps: pipe hoisting, pipe installation, elevation and axis control, pipe outer interface hanging net wiping tape, 180° guaranteed concrete pouring, and pipe inner interface wiping tape.

Specifically, the step 7) includes the following steps: backfill medium-coarse sand evenly on both sides of the installed pipeline, each layer of backfill thickness is 500 mm, and water and tamp layer by layer, the dry weight of the medium-coarse sand backfilled is greater than or equal to 16KN/m³; when backfilling to 500 mm above the top of the pipeline, backfill with soil excavated from the excavation trench to the original ground level, backfill symmetrically on both sides of the excavation trench and compact it in layers.

The beneficial effect of the present invention is that: the present invention can save cost to a great extent, shorten construction period, reduce construction difficulty and reduce potential safety hazards.

Due to the deep foundation pit open excavation pipeline construction process under rich water and complex rock and soil geological conditions, the foundation pit needs to be supported and water-stopped, otherwise the pipeline installation operation cannot be carried out, and the Larsen steel sheet pile support construction steel sheet pile cannot Into the rock, especially in the case of uneven cross-section of the lower rock formation, there is a large gap between the lower end of the steel sheet pile and the rock formation, resulting in poor water-stop effect and large water output, which affects the operation during trench excavation and pipeline installation. Larger safety hazards, and after installing steel purlins and steel supports, the stonework at the lower part of the trench is difficult to break with machinery and can only be broken manually. When encountering weakly differentiated rock formations, the efficiency of manual work is poor, which seriously prolongs the The construction period increases the construction cost and makes the construction more difficult.

The "dark cofferdam" construction method of the present invention is to replace the unfavorable soil layers on both sides of the ditch with cement and plain soil mixture mixed in advance, and layer and compact to form a dark cofferdam to achieve the water-stop effect. , In the process of trench excavation, spray anchors to the slope, and break the lower rock formation with a breaker. The construction process is simple, the construction difficulty is low, the demand for mechanical equipment is small, the construction period is shortened, the construction cost is saved, and it is safe and effective.

Description of drawings

The specific embodiment of the present invention will be further described below in conjunction with accompanying drawing, wherein:

Fig. 1 is a schematic diagram of the excavation line setting-out on both sides of the excavation trench in the present invention;

Fig. 2 is a schematic diagram of layered slope excavation in an excavation trench according to the present invention.

detailed description

A kind of road construction method that is applicable to the open-cut pipe of compound stratum of the present invention, concrete construction operation steps are as follows:

(1) Measuring and setting out

With reference to shown in Fig. 1, according to the well position of the inspection well 2 on the construction site and the depth of excavation trench 1, release the snail layer on both sides of excavation trench 1, the excavation line 3 of 2 meters wide of liquefied soil layer, The width d of the excavation trench is determined by the requirements of the construction pipeline, and the excavation line 3 is sprinkled with lime powder to avoid under-excavation or over-excavation.

(2) Replacement of the mixture in the excavation line on both sides of the excavation trench

①Excavation of snail layer and liquefied soil layer: Excavation is carried out from top to bottom. According to the excavation line, the upper soil layer inside the excavation line is first removed, and then the snail and liquefied soil layer are excavated. The width of the excavation line is 2m , and excavate every 20m as a section. During the excavation process, it is strictly forbidden to over-excavate the side or bottom to stabilize the soil layer, and the excavation depth is strictly controlled. On-site excavation and transportation are carried out, and dump trucks are used to transport them to designated locations for centralized stacking to avoid environmental pollution.

② Cement and soil mixture replacement construction: Immediately after the snail layer and liquefied layer soil layer are removed, the pre-mixed cement and plain soil mixture shall be backfilled and compacted in layers (the ratio of cement participation is: cement mass: plain Wet mass of soil = 10%-15%) to prevent collapse and affect the water-stop effect; the thickness of each layer of paving is 500-800mm, and after each layer of paving is completed, it is rolled by an excavator, and then compacted with a vibrating ram , the number of rolling and tamping times for each layer is not less than 3-5 times.

(3) Slope excavation of the upper soil layer

Referring to Figure 2, the trenches in the excavation section are excavated by grading, with a slope of 1:0.5. During the excavation process, the excavation sideline is strictly controlled, and the construction is carried out in sections according to the above-mentioned 20m replacement construction. After the pipeline installation is completed, the next section of earthwork excavation is to be carried out. Over-excavation is strictly prohibited to prevent the excavation of the cement and plain soil mixture that has been replaced and the water-stop effect will not be achieved.

Since the upper 3-5m range of the excavation trench is poor soil layer, the water output is large, and the stability of the slope is poor. In order to prevent the slope from being washed by the rainwater and cause the slope to slide, immediately spray the repaired slope with a net after excavation. Concrete: that is, wedging bars with a diameter of 10mm and a length of 40cm vertically on the slope, with a vertical and horizontal distance of 1m between the bars, and laying a layer of Φ1*40*40 steel wire mesh 4 on it. After the steel mesh 4 is hung, it can be sprayed Concrete, the concrete strength is C20 fine stone concrete, and the thickness is 100mm.

(4) Grading and excavation of the lower rock formation

After the slope excavation of the upper soil layer is completed, in order to prevent the upper unfavorable soil layer from causing local collapse during the rock layer breaking process and affecting the construction, when the weathered rock and limestone layers are excavated, a 1m step 5 is left on each side, and a breaker is used to Break the rock formation and excavate according to 1:0.5 grading, strictly control the base elevation during excavation, and over-excavation is strictly prohibited.

(5) Replacement of sand and gravel at the bottom of excavated trench foundation pit

When breaking the rock formation with a breaker, the elevation of the bottom of the foundation pit should be 600mm lower than the elevation of the bottom of the installation pipeline 6. After the destruction is completed, replace and level the foundation pit with sand and gravel to the design elevation of the bottom of the pipeline 6, so as to prevent the pipeline 6 from sinking during the pipeline installation process.

(6) Pipe installation

Follow the steps below: pipe hoisting→pipe installation→elevation, axis control→pipeline external interface hang net wiping tape→180°pipe guarantee concrete pouring→pipe inner interface wiping tape.

(7) Medium-coarse sand and earthwork backfill

On both sides of the installed pipeline, medium-coarse sand is evenly fed and backfilled. The thickness of each layer of backfill is 500mm, and it is watered and compacted layer by layer. The dry weight of the backfilled medium-coarse sand is greater than or equal to 16KN/m³; backfill to 500mm above the top of the pipeline. When using the excavated trench, backfill it with the soil excavated to the original ground level, backfill symmetrically on both sides of the excavated trench and tamp it layer by layer.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention, All should be covered within the protection scope of the present invention.

Claims (6)

1. A construction method suitable for open-cut pipelines in composite strata, characterized in that it may further comprise the steps: 1) Measurement and setting out: According to the well position of the inspection well on the construction site and the depth of the excavation trench, measure and release the 2-meter-wide excavation line of the snail layer and liquefied soil layer on both sides of the excavation trench; 2) Replacement of the mixture in the excavation line on both sides of the excavation trench: according to the excavation line from top to bottom, first excavate the upper soil layer in the excavation line, and then remove the lower snail layer 1. Excavation of the liquefied soil layer; when the snail layer and the liquefied soil layer have been excavated, backfill and compact the mixture of cement and plain soil prepared by mixing in advance, and the thickness of each layer of paving is 500-800 mm. After layer paving is completed, an excavator is used for rolling, and then a vibratory tamp is used for compaction. The number of times for each layer of rolling and compaction is greater than or equal to 3-5 times; the mass ratio of cement in the mixture to the wet mass of plain soil 10% to 15%; 3) Slope excavation of the upper soil layer: the upper soil layer in the excavation trench is excavated according to the slope of 1:0.5, and the slope of the upper soil layer is treated with hanging net spraying concrete after excavation; 4) Slope excavation of the lower rock layer: When excavating the upper soil layer in the trench to the Fenghua rock and limestone layer, leave a step with a width of 1 meter on both sides of the trench, and then use a breaker to break the rock layer below the step. Grading and excavation according to the slope of 1:0.5; 5) Replacement of sand and gravel at the bottom of excavated trench foundation pit: After the excavation of the rock layer is completed, replace and level the bottom of the foundation pit with sand and gravel to the preset elevation of the bottom of the pipeline; 6) Pipeline installation; 7) Medium-coarse sand and earthwork backfill. 2. A construction method suitable for open-cut pipelines in composite strata according to claim 1, characterized in that the excavation line is sprinkled with gray and white powder. 3. A construction method suitable for open-cut pipelines in composite strata according to claim 1, characterized in that, in the step 2) and step 3), the 20-meter-long excavation trench is divided into one section and divided into two sections. segment excavation. 4. A construction method suitable for open-cut pipelines in composite strata according to claim 1, characterized in that, in the step 3), the sprayed concrete treatment steps are as follows: Wedging several diameters 10 vertically on the slope surface mm, 40 cm in length, the vertical and horizontal spacing of the bars is 1 meter, and a layer of Φ1*40*40 steel wire mesh is laid on each of the bars, and the concrete can be sprayed after the net is hung. The concrete is of strength C20 Fine stone concrete, the concrete spraying thickness is 100mm. 5. A construction method suitable for open-cut pipelines in composite strata according to claim 1, characterized in that the step 6) is carried out according to the following steps: pipeline hoisting, pipe installation, elevation and axis control, pipeline external interface Hanging net wiping tape, 180° guaranteed concrete pouring, and pipe inner interface wiping tape. 6. A construction method suitable for open-cut pipelines in composite strata according to claim 1, characterized in that the step 7) includes the following steps: uniformly blanking medium coarse sand and backfilling both sides of the installed pipeline at the same time , the backfill thickness of each layer is 500 mm, and watering and compacting layer by layer, the dry weight of the medium-coarse sand backfilled is greater than or equal to 16KN/m³; when backfilling to a position 500 mm above the top of the pipeline, use the soil excavated from the excavation trench to backfill to the original ground Elevation, backfill symmetrically on both sides of the excavated trench and compact it layer by layer.