CN217104953U - Sand dam constructed by adopting natural sedimentation graded poor fine sand on site - Google Patents

Abstract

The utility model discloses a sand dam constructed by adopting natural siltation graded poor fine sand, though the volume is large, according to the design of one century flood with water level fluctuation of 9m a day, especially utilizing natural siltation fine sand, the percentage of occupation is up to 58%, does not destroy cultivated land, does not waste loam resource, and has the advantages of rapid construction progress, extremely low investment, safety, economy and outstanding comprehensive benefit; the need of large-scale transportation and large stock ground is avoided; excavating and replacing soil without a foundation; the sand dam is filled more than one time before the flood season, the safety is ultrahigh, cofferdams are not constructed at the upstream and the downstream of the sand dam, the requirements of foundation pit excavation and electricity conservation and drainage are avoided, the whole year is finished, and the construction period is saved by at least 1.5 years; the method has the advantages of wide working face, easy comprehensive spreading, simple technical operation, suitability for rural migrant participation construction and capability of making up the loss of land acquisition and migration parts of reservoir construction. In a word, the utility model discloses can solve migration protection engineering dam type and consume a large amount of manpower, material resources, extravagant a large amount of loam resources, the construction link, disturb many, construction period is long, the high scheduling problem of engineering investment.

Description

Sand dam constructed by adopting natural sedimentation graded poor fine sand on site

Technical Field

The utility model relates to a water conservancy, hydroelectric engineering construction land acquisition immigration settles planning design protection engineering technical field, and specifically speaking relates to an adopt sand dam that natural siltation graded bad fine sand was built on the spot.

Background

The reservoir construction of China is close to more than 10 thousands of seats, wherein the number of large and medium-sized reservoirs exceeds 0.47 thousands of seats, and a large amount of technical and economic certification problems of protection and relocation schemes exist in the reservoir construction process. The water conservancy and hydropower engineering construction land acquisition submerging treatment standard requirement is as follows: the method has protection conditions for important objects in the CLY (reservoir section and reservoir bay shallow water temporary inundated area), is feasible in technology, economical and reasonable, and needs to take protection measures. Therefore, the method is important and sensitive to the migration task of the population migration line of the reservoir, is wide in related range, and is used for selecting the most suitable migration protection engineering dam type scheme under the normal reservoir operation condition in combination with the local actual environment when protection is required in the reservoir construction characteristic region, so that the method is thorough in technology, safe, reliable, economical and reasonable. The utilization and treatment of a large amount of deposited fine sand covering layers on the riverbed are related to the safety and economy of the immigration protection project, and have great influence on dam site, dam type selection, construction period, construction cost and the like, so that the method is one of the key technical problems which are related to the establishment, the vital importance and the mutual restriction of the immigration protection project.

Under general circumstances, the first consideration in the protection engineering scheme for immigration is that local material dike dam types are adopted, such as homogeneous earth dams, sand gravel clay core wall dams, slurry stone dams and the like, which are all commonly used dike dam types to meet the economic rationality requirement of the protection engineering scheme for immigration, the dike dam materials generally adopt local clay loam, sand gravel, stone materials and the like, but the dike dam types carry out foundation cleaning treatment on the silted covering layer in the riverbed at different degrees or consume a large amount of loam sources, which often brings many adverse effects, for example, the excavation amount of the covering layer is large, and the excavation period is long; cofferdam engineering needs to be set, and even the cofferdam engineering scale is increased, so that the cofferdam is difficult to arrange, the seepage-proofing treatment task is heavy, and the drainage of a foundation pit is large; the excavation of the covering layer causes the side slope of the foundation pit to be overhigh, so that the integral stability of the side slope of the backwater side of the cofferdam and the side slope of the foundation pit is influenced; the cover layer excavation work amount is large, the waste material is large, the scale of the waste slag yard is correspondingly increased, and the arrangement of the waste slag yard is more difficult; the excavation depth of the covering layer is large, and the road of the lower foundation pit is affected by the longitudinal slope and is difficult to arrange; the scale of excavation and various projects influenced by the excavation is increased, the construction links are more, the project management is complex, and the project investment is increased. In a word, the conventional dam models are required to implement soil replacement measures of different degrees on the foundation covering layer, particularly, the fine sand covering layer is required to be completely cleaned, the foundation is dug and filled once, even segmented cofferdam construction is required, construction interference is prominent, construction operation procedures are more, time and labor are consumed, a large amount of loam or slag materials are temporarily stacked, the occupied and reclaimed farmland task amount is large, the construction period is long, auxiliary projects are more, the requirement on construction management level is higher, the project investment cost is higher, even the problems that a dam site needs to be replaced and the like are caused due to overhigh investment compared with a dam model selected, and the immigration protection project loses the standing condition.

Based on the circumstances, the utility model provides an adopt sand dam that natural siltation gradation harmfully fine sand was built on the spot can effectively solve above problem.

SUMMERY OF THE UTILITY MODEL

To the not enough that exists among the prior art, the utility model aims to provide an adopt the sand dam that the bad fine sand of natural siltation gradation was built on spot to solve the immigration protection engineering dykes and dams type that proposes usually among the above-mentioned background art and consume a large amount of manpowers, material resources, extravagant a large amount of loam resources, the construction link, disturb many, the construction period is long, the high scheduling problem of engineering investment.

In order to achieve the above purpose, the utility model discloses a following technical scheme realizes:

the sand dam constructed by adopting the natural siltation graded poor fine sand comprises a foundation stratum, a natural sand-gravel layer formed on the foundation stratum, a natural siltation fine sand layer formed on the natural sand-gravel layer and a filling fine sand layer filled on the natural siltation fine sand layer, wherein both the inner side and the outer side of the sand dam are provided with revetments.

Preferably, a dam waist berm is arranged on the slope protection outside the sand dam, the slope ratio from the dam abutment outside the dam crest to the designed water level is 1:2.5, the slope ratio from the designed water level to the dam waist berm is 1:3, and the slope ratio from the dam waist berm to the toe outside the dam is 1: 3.5.

Further preferably, the dam outer side slope protection of the sand dam adopts a rock block slope protection, and the rock block slope protection comprises a sand and gravel reverse filter layer, a broken stone cushion layer and a dry masonry layer which are sequentially arranged from bottom to top.

More preferably, a drainage overflow belt is arranged in the waist section of the slope protection outside the dam, the drainage overflow belt slightly inclines outwards, and the outer end of the drainage overflow belt is connected and communicated with the slope protection gravel reverse filtering layer.

Preferably, a slope protection foundation which is arranged parallel to the axis of the sand dam in the through length mode is arranged at the position of the outer slope toe of the sand dam, and a deposition area for preventing the outer slope toe of the dam from sinking and horizontally preventing seepage and paving in front of the dam is formed close to the outer side of the slope protection foundation.

Preferably, the slope protection foundation is of a dry-masonry block structure, the bottom of the slope protection foundation needs to be deep into the position which is at least 1.5m below the top line of the natural sand-gravel layer, so that the height of the whole horizontal straight line of the slope protection foundation is horizontally arranged, the width of the top surface is 1.5m, and the width of the bottom is not less than 2 m.

It is further preferred that the deposition zone has a width not less than 30m in a direction perpendicular to the dam axis.

Preferably, the slope protection at the inner side of the dam of the sand dam is implemented by turf slope protection, and the slope ratio from the dam shoulder at the top of the dam to the slope toe at the inner side of the dam is 1: 2.75.

Further preferably, a drainage ridge is arranged at the toe of the inner slope of the dam of the sand dam, and the height of the drainage ridge is 1.2m and is consistent with the structure of the block stone protection slope outside the dam.

It is further preferable that the width of the foot-off in the direction perpendicular to the dam axis is not less than 50 m.

Preferably, different medium loam transition sections are arranged at the joint of the dam abutment of the sand dam and the bank mountain rock mass, manual compaction is adopted, the width of the dam in the axial direction is not less than 5m, when the dam abutment is connected with an original ground line loam layer, a humus layer on the inner surface of the original ground is required to be removed, when the collision end point is the mountain rock mass, a winding seepage prevention measure is required, at least one vertical groove needs to be dug on the mountain rock mass, and the loam is manually filled and compacted in the range of the groove.

Adopt the utility model discloses, expropriate land to move the people to settle and plan certain sand dam protection engineering to certain super-huge reservoir construction and carry out technical research and test, its engineering dam address district fine sand overburden is up to 13m thickest, and this sand dam fine sand structures total height 23.1m single day flood water level fluctuation is 9m the biggest, has CLY and adopts the representativeness of fine sand filling sand dam protection engineering. And (3) adopting slope stability analysis and calculation software to perform stability calculation on the dam slope of the sand dam under various working conditions, and determining that the outer dam slope of the sand dam is 1: 2.5-1: 3.5 and the inner dam slope is 1: 2.75.

Through research and analysis the utility model discloses its advantage of technical scheme and positive effect as follows:

in the technical scheme, one of the most adverse key factors is that the adverse effect on the stability of the dam slope when the flood of the mountain area river reservoir rises and falls by 9m per day can be resisted, and through stable calculation, the calculation safety coefficient of the sliding stability of the inner dam slope and the outer dam slope of the sand dam meets the standard requirement.

In the technical scheme, the permeability coefficient of a natural sand-gravel layer of the foundation is far greater than that of fine sand-gravel bodies deposited on the upper part of the foundation, relatively speaking, the fine sand bodies on the whole upper part are also anti-seepage body materials, the fine sand dam bodies are not main seepage channels, the foundation sand-gravel layer is the main seepage channels, and a large-size sand dam is constructed by utilizing a large amount of naturally deposited fine sand bodies, so that the quality can be changed in quantity, the fine sand bodies of the sand dam can be used for slope and seepage stability, meanwhile, the seepage diameter of the sand-gravel layer of the main seepage channels of the foundation of the sand dam is further prolonged, and the exposed sand-gravel layer of a soil pit behind the dam cannot be firstly subjected to seepage damage.

The cover-free excavation engineering quantity of the sand dam immigration protection engineering is designed for the land acquisition immigration placement planning of the super-huge reservoir construction, the quantity of fine sand in the inner slope toe and the outer slope toe of the sand dam is more than a natural sand pebble layer, the sand dam body utilizes 58% of naturally deposited fine sand (containing mineable fine sand within 50m beyond the inner slope toe and the outer slope toe of the dam), the soil taking quantity of a soil taking pit only accounts for 42% of the total earth filling engineering quantity of the sand dam, the construction period is at least shortened by 1.5 years, the temporary slag field setting required by foundation cleaning of the water-free engineering is adopted, the auxiliary engineering such as large-scale foundation soil changing, cofferdam drainage and the like which is not adopted by the conventional water conservancy and hydropower engineering is completed in the same year, and about 40 ten thousand m of fine sand is completed in the same year ³ The sand dam immigration protection project is characterized in that a soil taking pit 31.87 mu of land is arranged outside the foot forbidden land 50m behind the toe in the dam only because of insufficient filling of a sand source.

According to the technical scheme, the direct engineering investment of the sand dam only accounts for 39% of the investment of a stone-masonry-compared dam-shaped scheme, the stone-masonry-compared dam-shaped scheme is small in section, narrow in construction surface, multiple in construction links, complex in underwater foundation cleaning, and auxiliary engineering such as cofferdams must be arranged.

The direct engineering investment of the sand dam in the technical scheme is greatly saved, if important and sensitive objects protected by the sand dam are remotely moved, the investment of the immigration protection engineering sand dam only accounts for 15.86% of the investment of the scheme of remotely moving the towns, the functions of the original towns such as water and land transfer, storage and collection, industrial and commercial services, administrative centers and the like are reserved, and the difficulty of unstable production and arrangement after remote transfer and market transfer in the scheme of remotely moving the towns is avoided.

Drawings

FIG. 1 is a schematic diagram of a river entering river terrain and a sand dam arrangement range before a typical sand dam is constructed;

FIG. 2 is a cross-sectional view taken along line I-I of FIG. 1;

FIG. 3 is a diagram showing the grading curves of the sand and gravel coating particles and the upper and lower envelope design of the sand and gravel reverse filter layer;

FIG. 4 is a schematic diagram of a slope stability calculation of a sand dam;

FIG. 5 is a schematic diagram of calculation of an on-way water head of a simulated overflow section from an inner toe of a sand dam to a soil pit;

FIG. 6 is a diagrammatic view of FIG. 5 at A;

FIG. 7 is a water level connection diagram of each observation pipe of the sand dam;

FIG. 8 is a topographical view of a sand dam after the completion of a research test;

FIG. 9-1 is a cross-sectional view of a typical sand dam (01);

FIG. 9-2 is a cross-sectional view of a typical sand dam (02);

FIG. 10 is a perspective view taken at B in FIG. 9-1;

fig. 11 is a view showing a large scale at C in fig. 9-1.

Reference numerals: 1-designing water level; 2-dam axis; 3-emphasis of protection range; 4-stone masonry water retaining section; 5-a soil sampling pit; 6-loam transition section; 7-flood discharge ditch; 8-flood discharging culverts; a 9-basal rock layer; 10-a natural sand-pebble layer; 11-a deposition zone; 12-slope protection foundation; 13-stone slope protection; 131-sand and pebble reverse filtering layer; 132-a gravel cushion; 133-dry masonry layer; 14-naturally silted fine sand layers; 15-original ground line; 16-filling a fine sand layer; 17-a drainage overflow belt; 18-dame waist packway; 19-dam crest; 20-turf slope protection; 21-drainage prisms; 22-foot forbidden ground; 23-a water level observation tube; 231-a first sight tube; 232-a second sight tube; 233-a third observation tube; 234-a fourth sight tube; 235-a fifth sight tube; 236-sixth observation tube.

Detailed Description

In order to make the technical solution of the present invention better understood by those skilled in the art, the following description of the preferred embodiments of the present invention is given with reference to the accompanying examples, but it should be understood that the drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.

The utility model utilizes a large amount of silted graded bad fine sand on site, especially does not carry out underwater foundation cleaning and soil replacement, uses a fine sand covering layer as a foundation part sand dam body, and directly mines nearby fine sand on the upper part to fill and build a dam, thereby not only ensuring the stability of the side slope of the sand dam and the stability of the ground penetration, preventing the liquefaction of the sand dam, having no auxiliary projects such as large-scale cofferdam drainage and the like in the conventional water conservancy and hydroelectric engineering, reducing the construction links, quickening the construction progress, reducing the dosage of loam (or other filling materials for building the dam), protecting cultivated land, greatly reducing the problems of engineering cost and the like, especially providing a dam type selection scheme which is feasible on site and has excellent economy for land acquisition and migration placement of water conservancy and hydroelectric engineering construction, ensuring the production of the back-leaning migrant, basically stabilizing the living environment, continuously and normally playing the original social functions, simplifying the construction process and the open construction operation face, the method is suitable for local rural immigration to participate in intensive labor investment, increases the rural immigration economic income, fully and timely embodies social and economic benefits of immigration protection engineering construction, and jointly builds and shares economic construction development achievements.

The embodiments of the present invention will be described in detail below with reference to certain sand dam planning designs, technical studies and tests, and the accompanying drawings, but they do not constitute limitations of the present invention, which are given by way of example only, and the advantages of the present invention will become clearer and more easily understood by way of illustration.

As can be seen from fig. 1 and 2, the first-level stage of the right bank is about 20 meters wide and is about 175m high at the place where the town is below the population migration line of reservoir construction land acquisition, the fine sand in the riverbed below 175m accounts for 63.6%, the sand-gravel layer accounts for 16.5%, and the first-level loam of the left bank and the right bank accounts for 19.9%. Therefore, the sand dam is built near the town, the locally available naturally silted fine sand resources are rich, and when the flood of the external river is controlled, the cecal silting phenomenon is easily formed at the junction of the branches, at the moment, the silting ratio of the fine sand is higher, so that the opportunity is properly mastered, when the flood of the external river disappears, the sand dam is built, the construction is completed in the year, the earthwork quantity is minimum, namely when the water level of the external river is low, a large amount of naturally silted fine sand is taken away due to long-term clear water drainage of the water flow in the interval, as shown in a left groove in a figure 2 (longitudinal 1: transverse 2.5, unit: m), namely the phenomenon formed under the cutting action of clear water drainage of two hydrology years, and the lost fine sand accounts for 21.9% of the still-stored fine sand.

The utility model provides an adopt the sand dam that bad fine sand of natural siltation gradation was built on spot, the sand dam includes bed rock layer 9, is formed at natural sand cobble layer 10 on bed rock layer 9, is formed at natural siltation fine sand layer 14 on natural sand cobble layer 10 and fills the fine sand layer 16 of filling on natural siltation fine sand layer 14, the dam inside and outside both sides of sand dam all are equipped with the bank protection.

The construction method comprises the following steps:

1) for a certain oversize reservoir, taking a sand dam protection engineering design water level 1 according to a one-hundred-year-round reservoir backwater curve (considering the conditions of maximum incoming quantity of warehousing flood, corresponding reservoir water level and the like with certain frequency, various possible water level and flow combination conditions, and then taking a backwater water level connection line of the highest reservoir along the way), and considering 2m safety superelevation;

2) the position of an axis 2 of the sand dam is selected to be related to the size of an important sensitive object protection range of a immigration protection project, the safety of the project and the like, the immigration protection project is brought into an important protection range 3, the ratio of the important sensitive object protection range to an important sensitive ballast collecting range to be protected is not less than 70%, when the axis 2 of the sand dam passes through the important sensitive ballast collecting range, a grouted stone water retaining section 4 is adopted, the occupied area size of a project structure is greatly reduced, and the land acquisition and removal amount of the project construction is reduced, as shown in figure 8;

3) when the masonry water retaining section 4 level-crosses the main municipal traffic road as a protection object, two stop log gate grooves are arranged, once the flood of the external river exceeds the warning water level, the two stop log gates are closed, the prefabricated reinforced concrete stop logs are quickly installed in the reserved gate grooves, flood prevention soil is filled between the two stop log gates to form the stop log gate for temporarily retaining the flood, and the stop log gate is removed after the flood is removed and the municipal traffic is recovered, as shown in fig. 8;

4) selecting the initial period of the dry season to start to carry out the main engineering construction of the sand dam, aiming at a one-time closure construction scheme, before a diversion facility is not completed in the construction period, the problem of temporary water interception of an upstream interval behind the sand dam exists, a step-by-step temporary water interception measure is made in the interval above the sand dam, a temporary interception and storage dike is respectively arranged at the outlets of two main stream ditches for water inflow in the upstream interval, a temporary interception and storage dike is also arranged when a flood discharge ditch 7 is close to the sand dam, the storage capacity of a deep pool groove in the interval of an upstream river far away from the sand dam is exerted, so that the upstream flood discharge ditch 7 is almost cut off, and the underground water level behind the dam in the sand dam period is effectively reduced, as shown in figure 8;

5) setting a sedimentation area 11 for preventing the falling of the toe foundation outside the dam and horizontal seepage-proofing paving in front of the dam on the outer side of the foundation close to the dry masonry revetment 13, wherein the width of the sedimentation area is not less than 30m in the direction vertical to the axis of the dam, as shown in figure 9-1;

6) a rock groove is dug in a slope toe of a mountain body of a left bank of a sand dam, which belongs to the area of the left dam, a diversion culvert is arranged in the construction period of the sand dam, and the construction of the sand dam is converted into a flood discharge culvert 8 after the construction of the sand dam is finished (generally, a rigid structure is not suitable to be arranged in the sand dam along the line, although the flood discharge culvert longitudinally penetrates through the sand dam, the construction of filling soil materials of the sand dam is continuously finished at the upper part of the flood discharge culvert because the foundation of the flood discharge culvert is bedrock and is of a gate arch and masonry structure, and the flood discharge culvert is embedded into the excavated mountain body rock groove and only receives the vertical gravity of fine sand filled at the upper part, and the adverse effect of large uneven settlement cannot be generated after the sand dam is built. The minimum distance between the outlet position of the flood discharge culvert 8 and the direction of the slope toe slope protection foundation 12 outside the dam perpendicular to the axis of the dam is 30m, when the distance is insufficient or a section of the slope toe slope protection foundation is impacted by flood top, stone throwing and bottom protection are carried out in a flushing pit or a related section, the adverse erosion influence on the stability of the sand dam slope protection foundation 12 during flood discharge is prevented, the minimum block diameter of the stone throwing is not less than 50cm, the thickness is 2m, and the uniaxial saturated compressive strength of the block stone is greater than 30MPa, as shown in figure 9-2;

7) the construction safety of the high slope is ensured when the mountain body of the flood discharge culvert 8 is dug, the construction of the flood discharge culvert 8 is completed 1 month before the main flood season, the diversion is put into use, and the project progress is reversed according to the requirement;

8) controlling the filling process of the earthwork engineering of the main body of the construction sand dam, ensuring that when the controllable water level at the outer side of the sand dam rapidly rises in flood season, the rising height of the whole dam section exceeds the natural flood standard in design construction season, and under the condition of reserving necessary safety superelevation, the outer side of the sand dam is not required to be provided with a downstream cofferdam;

9) when the graded poor fine sand in the sedimentation zone 11 is moderately exploited according to the requirement of filling the graded poor fine sand in the sand dam, the exploitation is stopped when the natural sand pebble layer 10 is deep, and the erosion of a downstream riverbed to the direction of the sand dam is reduced;

10) taking a natural silting fine sand layer 14 as a construction foundation, mining poor fine sand below an original ground line 15 (distributed along the direction II-II in the figure 1) and outside a toe line of an inner slope and an outer slope of the dam of the sand dam in an upper dam by matching, filling a fine sand layer 16 of the sand dam, supplementing the reserve of a mining soil taking pit 5 when the filling amount is insufficient, and filling the fine sand layer to the top 19 of the sand dam;

11) when the poor-graded fine sand is mined within the range from the outside of the toe of the inner slope of the sand dam to 50m, the thickness of a covering layer on the natural sand gravel layer 10 is not less than 7 m;

12) the dam waist berm 18 outside the sand dam is horizontally arranged with the ratio of the lower dam slope to the designed water level 11 being 1:3, the ratio of the upper dam water level 1 to the dam crest 19 outer dam abutment slope being 1: 2.5;

13) the slope ratio of the sand dam at the inner side of the sand dam is 1:2.75, a turf protection slope 20 is adopted, and a drainage ridge body 21 is arranged in the toe area in the dam;

14) the inner and outer slope toes of the dam are respectively extended within 50m in the direction vertical to the axis of the dam, and the sand dam plane arrangement dam at two dam ends is respectively extended within 50m in the direction vertical to the axis of the dam, so that the range of a project foot forbidden land 22 is provided, a post-dam grading bad fine sand soil pit 5 is arranged outside the foot forbidden land 22, and a humus layer soil body is not allowed to go to the dam;

15) performing foundation cleaning and building on the slope protection foundation 12 outside the dam, wherein the slope protection foundation 12 is of a dry block stone structure, the height is at least 1.5m, the width of the top surface is 1.5m, the bottom of the slope protection foundation 12 needs to be deep into the position 1.5m below the top surface line of the natural sand gravel layer 10, so that the slope protection foundation 12 is horizontally arranged in an equal elevation mode in a horizontal straight line mode, and the top surface is horizontally arranged to be parallel to the axis 2 of the sand dam; the slope protection foundation 12 needs to be completely embedded in the natural sand and gravel layer 10, as shown in fig. 11;

16) the sand and gravel-containing inverted filter 131 and the gravel cushion 132 are laid on the block stone revetment 13 outside the sand dam which is basically synchronously carried out with the filling and rising of the dam body of the sand dam, and the dry block stone layer 133 is laid and protected, and the horizontal connection length is not less than 1.5m when the sand and gravel inverted filter 131 at the position of the revetment foundation 12 is connected with the natural sand and gravel layer 10, as shown in figure 10;

17) the thickness of the rock block revetment 13 outside the dam is 1.2m, wherein the thickness of the sand-gravel inverted filter layer 131 is 0.5m, the thickness of the rock block cushion layer 132 is 0.2m, and the thickness of the dry rock block layer 133 is 0.5m, the revetment is strictly arranged layer by layer according to the sand-gravel inverted filter layer 131, the rock block cushion layer 132 and the dry rock block layer 133 in sequence, the long edge dimension of the rock block required by the dry rock block layer 133 is not less than 50cm, the short dimension of the rock block is not less than 20cm, the uniaxial saturated compressive strength of the rock block is more than 30MPa, the rock block is vertically built on the long edge, no stacking is needed, particularly, the rock block at the lower part is not filled, and the surface layer at the upper part is covered by the long edge of the rock block;

18) when filling the waist section of the sand dam, a water level quick-falling gravel horizontal drainage overflow belt 17 is arranged, slightly inclines outwards, has the thickness of 1m and the width of 15m, and the outer end part is connected and communicated with a gravel reverse filtering layer 131 of the slope protection;

19) the width of the sand dam waist berm 18 is 5m, the sand dam waist berm is horizontally arranged and is consistent with the layered structure of the rock block revetment 13, as shown in figure 10;

20) when the sand dam filling exceeds the dam waist underpass by more than 18, or the whole filling elevation exceeds the elevation of the highest point of the original ground line 15, starting from about 50% of the designed dam height, blasting of the project or other project construction is strictly prohibited in the range of the foot-forbidden land 22, and the occurrence of vibration liquefaction of fine sand bodies with poor sand dam grading is avoided;

21) the dam parts at two ends of the sand dam are respectively connected with the mountain rock bodies (or rigid structures) at two banks, the transition sections 6 with different media are arranged, manual tamping is adopted, the length of the dam axis 2 direction is not less than 5m, the width of the dam axis direction is 6m, when the transition sections are connected with the 15 loam layer on the original ground line, the humus layer on the inner surface of the original ground is required to be removed, when the conflict endpoint is the mountain rock, a winding seepage prevention measure is required, at least one vertical groove needs to be drilled on the mountain rock body, the groove is 2m deep into the mountain rock body and 4m wide, the groove range is firstly manually filled and tamped with loam in a layering way, and the soil transition sections 6 are also required to be arranged between the stone slurry water retaining section 4 (or other rigid structures) and the fine sand layer 16 filled in the sand dam;

22) slope surface water diversion intercepting ditches are arranged at the proper positions of the hills above the connection positions of the two end parts of the sand dam and the mountain bodies and are guided out of the foot-forbidden land, so that adverse effects on the stability of the two dam end parts of the sand dam after the water on the slope surface is leaked and collected are prevented;

23) after the sand dam is basically finished, at least one row of internal dam water level observation pipes 23 are arranged on an edge line perpendicular to the axis 2 of the sand dam, 1 hole is arranged at the upper part and the lower part of a dam waist berm 18, 1 hole is arranged at the designed water level 1 part, 1 hole is arranged at the dam shoulder 19, 1 hole is arranged at the dam internal toe, and 1 hole is arranged near a soil taking pit 5, so that the seepage water pressure distribution condition in the dam body after the sand dam is built is observed, as shown in figure 7.

Key engineering measure design calculation

1. Dam body filling material, sand and gravel reverse filtering layer and selection of sand and gravel reverse filtering material field

1.1, dam body filling material:

the dam body of the sand dam is mainly formed by covering and filling riverbed sand with a cover layer. According to field tests, the riverbed sand coating is poor-graded fine sand with a non-uniformity coefficient D ₆₀ /D ₁₀ 1.71, coefficient of curvature (d) ₃₀ ×d ₃₀ )/(d ₆₀ ×d ₁₀ ) The grading curve is shown in fig. 3 (particle size on abscissa, unit: mm), the composition of the granules is shown in Table 1, wherein the water 1 is the sand and pebble sampling below the sand bag, and the water 2 is the codeAnd sampling the riverbed sand bag.

Table 1 riverbed sand coating and riverbed sand pebble coating particle composition table

1.2, designing and calculating a sand-gravel reverse filtering layer:

(1) calculation of control particle size of upper envelope and lower envelope of sand and gravel reverse filter layer

Sand and pebble inverted filter layer lower envelope D _15max

According to the soil conservation requirement, calculating the lower envelope D of the sand and gravel reverse filtering layer according to the following formula _15max 。

D _15max ＝4d ₈₅

In the formula, D _15max The allowable grain diameter of the lower envelope of the sand-gravel reverse filtering layer, and the soil with the grain diameter smaller than the allowable grain diameter accounts for 15 percent of the total soil weight. According to field tests, protected soil d ₈₅ Is 0.2 mm. Calculated, D _15max Is 0.8 mm.

② sand pebble inverted filter layer upper envelope D _15min

According to the water permeability requirement, calculating the sand and gravel reverse filter layer upper envelope D according to the following formula _15min 。

D _15min ＝5d ₁₅

In the formula, D _15min The allowable grain diameter of the envelope on the sand and pebble reverse filter layer, and the soil with the grain diameter smaller than the allowable grain diameter accounts for 15 percent of the total soil weight. According to field tests, protected soil d ₁₅ Is 0.09 mm. Calculated, D _15min Is 0.45 mm.

③ sand and pebble inverse filter layer lower envelope D _10max And D _60max

Calculating the lower envelope D of the sand-gravel reverse filtering layer according to the following formula _10max And D _60max 。

D _10max ＝D _15max /1.2

D _60max ＝D _10max ×6

Calculated, D _10max And D _60max 0.67mm and 4mm, respectively.

Sand and pebble inverse filter layer upper envelope D _10min

In order to control the separation in the sand-gravel reverse filtering layer construction, the lower envelope D of the sand-gravel reverse filtering layer is calculated according to the following formula _10min 。

D _10min ＝D _15min /1.2

In the formula, D _10min The allowable grain diameter of the envelope on the sand and pebble reverse filtering layer, and the soil with the grain diameter smaller than the allowable grain diameter accounts for 10 percent of the total soil weight. Calculated, D _10min Is 0.38 mm.

Sand and pebble reverse filter layer lower envelope D _90max

When D is used for controlling the separation in the sand-gravel reverse filtering layer construction _10min When the diameter is less than 0.5mm, the sand and pebble reverse filter layer is covered by a lower envelope D _90max The diameter was taken to be 20 mm.

Wire covering D on sand and pebble reverse filter layer _5min

In order to ensure the water permeability of the sand-gravel reverse filtering layer, the sand-gravel reverse filtering layer is covered with a wire D _5min Taken to be 0.075 mm.

Seventhly, covering lines D on the sand and pebble reverse filtering layer _60min

Calculating the sand and pebble inverse filter layer upper envelope line D according to the following formula _60min 。

D _60min ＝D _60max /5

Calculated, D _60min Is 0.8 mm.

(2) Drawing sand and pebble inverted filter layer upper envelope and lower envelope

And drawing an upper envelope and a lower envelope of the sand and gravel reverse filtering layer according to the key particle size, designing a grading curve of the sand and gravel reverse filtering layer, wherein the grading curve is shown in a figure 3, and the particle composition is shown in a table 2.

Table 2 table of sand dam block stone slope protection preliminary sand pebble inverted filter layer design particle composition

(3) Reasonability of sand and gravel reverse filtering layer with rechecking design

Earth-retaining property

D ₁₅ /d ₈₅ The soil conservation criterion is satisfied when the ratio of 0.65/0.2 is 3.25 < 4.

(ii) Water permeability

D ₁₅ /d ₁₅ The water permeability criterion is satisfied when the ratio of 0.65/0.09 is 7.22 < 8.

③ grading conditions

Non-uniformity coefficient: d ₆₀ /D ₁₀ ＝2.5/0.45＝5.56

Curvature coefficient: (D30 × D30)/(D60 × D10) ═ 1.2 × 1.2)/(2.5 × 0.45) ═ 1.28

Therefore, the uneven coefficient of the sand-gravel reverse filter layer is located in the range of 5-8, and the curvature coefficient is located in the range of 1-3, so that the gradation is good.

1.3, selecting a sand and pebble reverse filter stock site:

as can be seen from fig. 3, the comparison of the particle distribution lines of the riverbed sandy gravel covering layer and the sandy gravel reverse filtering layer design line shows that the proportion of coarse particles of the sandy gravel covering layer is less than 17.5% of the total soil weight of soil with a representative particle size of 5mm, and the corresponding proportion of the sandy gravel covering layer is 65%, mainly, the sandy gravel material selected by the former is selected in a small range, only the sampling is carried out in the vortex migration water flow sedimentation area at the merging port of the stream river, and the fine sand covering layer is arranged on the upper part of the sandy gravel covering layer, the water flow velocity is not high, and the fine particles are mainly deposited, so that the upstream torrent river section with larger slope drop near the riverbed is selected outside the vortex migration water flow sedimentation area at the merging port of the stream according to the requirement of the sandy gravel reverse filtering layer design, so as to increase the proportion of coarse particles, the design requirement is basically met through on-site screening verification, and the migration distance is within 5 km, and the sandy gravel reverse filtering layer can be used for the exploitation as a natural sandy gravel reverse filtering field.

2. Computational analysis of anti-slip stability of side slope of sand dam

2.1 calculation method

The anti-skid stability of the dam slope of the sand dam is researched and checked by adopting two programs of seepage analysis calculation and slope stability analysis in Beijing-Liang positive geotechnical engineering calculation analysis software (version 7.0).

2.2 mechanical parameters

The physical and mechanical parameters of the soil body are calculated and shown in the table 3.

TABLE 3 design values of physical and mechanical parameters of soil

2.3 calculation conditions

According to the design specifications of rolling earth-rock dams, the calculation conditions are divided into three types, namely normal operation conditions, abnormal operation conditions I and abnormal operation conditions II.

Wherein, the normal operating conditions include:

(1) in the stable seepage period (low water level 165m), the dam slopes on the water-facing side and the backwater side are stable.

(2) In the stable seepage period (the designed water level is 178.6m), the dam slopes of the water facing side and the backwater side are stable.

(3) In the stage of water level suddenly dropping (the water level drops by 178.6m → 169.6m, the flood lasts for 2 days), the slope of the upstream side dam is stable.

Very much the conditions I:

in the construction period (the water level is 158m in the construction period), the dam slopes on the water-facing side and the backwater side are stable.

Very good use of condition ii:

when the normal operating conditions meet the earthquake, the basic intensity of the earthquake at the location of the engineering area is VI degree, and the earthquake-resistant calculation can be omitted according to the earthquake-resistant design standard of hydraulic buildings.

2.4 calculating the section

The calculated profile is shown in FIG. 4 (units: m) according to the protective engineering layout.

2.5 calculation results

According to the design specification of the rolling type earth-rock dam, the level of a building of the sand dam is considered to be 5, and the checking and calculating result of the anti-skidding stability safety factor of the dam slope of the sand dam is detailed in a table 4.

Accordingly, the anti-skid stability safety coefficient of the dam slope meets the standard requirement under three calculation working conditions, and the control working condition is a water level sudden drop working condition.

TABLE 4 calculation results of anti-skid stability of dam slope of sand dam

Note: the basic earthquake intensity of the place of the engineering area is VI degree, and earthquake-resistant calculation can be omitted.

3. Infiltration analysis of earth-taking pit behind dam

3.1 computational sketch FIGS. 5 and 6 (Unit: m)

Designing an outer slope into three sections of 1:3.5, 1:3.0 and 1:2.5, calculating the slope of the diagram as 1:3.29, and obtaining the outer slope according to the height distribution weighted average; the toe part outside the dam is correspondingly simplified according to the unfavorable seepage stability condition; the elevation of the toe in the dam is 167.0m, and the calculation diagram is considered according to adverse factors when the covering layer is reduced to 165.0m, so that the top elevation of the covering layer behind the dam is consistent with the water level of the water taking pit; other design dimensions are unchanged. The calculation diagram is as follows.

3.2 calculating parameters and results

The parameters of getting are unanimous in calculation parameter and the side slope anti-skidding stability computational analysis of sand dam, the utility model discloses in, the interior toe of sand dam goes out overflow section along journey flood head calculation condition and calculation achievement to borrowing pit, see table 5.

TABLE 5 dam toe to borrowing pit overflow section on-way water head calculation parameter and result table

The overflow slope drop at the earth taking pit is checked and calculated to be 0.59% by an seepage flow analysis calculation program in Beijing-oriented positive geotechnical engineering calculation and analysis software (version 7.0), the weighted average slope drop from the toe in the dam to the overflow section of the earth taking pit is 9.53%, the slope drop is far less than 28.6-33.3% of the seepage allowable slope of the exposed gravel layer of the earth taking pit after the dam and is also less than 11.8% of the seepage allowable slope of the main fine sand filled in the dam, the calculation verifies that the seepage damage phenomenon does not occur in the area of the earth taking pit 5, the sedimentation area 11 is deposited immediately along with the construction of the sand dam, the formed horizontal seepage-proof cover in front of the dam is formed, the seepage-proof gravel layer seepage diameter of the foundation of the sand dam is further prolonged, and the seepage slope drop at the toe and the area of the earth taking pit 5 after the dam is more favorable.

Fig. 7 (unit: m) shows the observation results of the pressure observation pipes of the sand and gravel permeable layer of the dam body of the sand dam and the water level and slope connecting lines of the observation pipes in a certain experimental study, wherein each observation pipe 23 comprises a first observation pipe 231, a second observation pipe 232, a third observation pipe 233, a fourth observation pipe 234, a fifth observation pipe 235 and a sixth observation pipe 236 which are sequentially arranged from the outside of the dam to the inside of the dam. When the water level of the external river is 172.16m, the water level of each observation pipe is almost uniformly reduced from the outside of the dam to the inside of the dam after 20 years of construction of the site of the sand dam in the super-huge reservoir area, the elevation of the transition line of the mouth of the person is shown in figure 7, the water level of each observation pipe is only reduced from the outside of the dam to the inside of the dam, the hydraulic gradient rate of the infiltration section is relatively high, the hydraulic gradient is reduced from the outside of the dam to the inside of the dam approximately uniformly, the trend of the calculation result of the infiltration line of the dam is basically consistent with the trend of the calculation result of the infiltration line of the dam, the natural cobble layer of the foundation of the dam body of the sand dam is proved to be a main seepage water channel, the hydraulic gradient is proved to be relatively weak, the hydraulic gradient is reduced from the outside of the dam to the inside of the toe, the seepage stability of the dam is greatly influenced by the toe, the ground seepage from the toe to the seepage section of the inside of the dam, the hydraulic gradient is 3.55-8.62 percent, is slightly larger than the seepage calculation value of seepage, but is still far smaller than the seepage allowance of the seepage gradient of the seepage of the exposed sand layer of the earth pit behind the dam, the seepage allowance of 28.6-33.3 percent of the seepage allowance of the earth fill of the earth, the preset judgment of seepage stability of the escape section of the earth taking pit behind the dam is verified.

The experimental results of multiple times of actual measurement of the permeation and escape results of the exposed sandy cobble layer at the bottom of the soil taking pit also verify the conclusion that when the flood outside the sand dam is in the process of falling, the phenomenon of sand-turning and water-blowing is found in the soil taking pit behind the dam, the trend is obviously weakened along with the gradual increase of the water level of the soil taking pit, the sand-turning and water-blowing gradually becomes clear, and the particle separation test is carried out on the cone deposited around the bubbling point of the soil taking pit, so that the average particle size is 0.038mm, the maximum particle size is 0.1mm, the soil is light powdery loam, and no sandy cobble particles move.

After a plurality of times of large water heaving tests, the sand dam is re-deposited along with the mud flat on the outer side of the dam to form a new and natural fine sand horizontal cover, the thickness of the re-deposited fine sand layer exceeds 4m, the phenomena of sand removal pit sand removal, sand turning and water blowing behind the dam are gradually reduced, the main channel for natural sand gravel permeation of the sand dam foundation is further prolonged, the seepage diameter length is increased to exceed 30m, the phenomena of sand removal pit sand removal, sand turning and water blowing outside the foot forbidden area of the sand dam are relieved, the phenomenon of centralized sand removal, sand turning and water blowing in the soil pit disappears at last after a plurality of floods, the fact that the sand dam is built by adopting a large amount of natural deposited fine sand is verified, the slope is relieved, the seepage diameter is prolonged, the construction links are reduced, the construction links are fast, safe and economical, and the correctness of the design concept of construction investment is saved.

4. Sand dam earthquake liquefaction anti-seismic design

The sandy soil seismic liquefaction is caused by pore pressure rise and shear strength (or shear rigidity) reduction of saturated sandy soil under static or dynamic action (including seepage action) generated by earthquake and tends to disappear, and is represented by water spraying and sand blasting, loss of bearing capacity and flowing deformation.

The fine sand used for damming is newly deposited in the fourth line when being deposited, the mass percentage of the content of particles with the particle diameter smaller than 0.005mm in the soil is 7.7 percent (the content is 16 percent corresponding to the earthquake motion peak acceleration of 0.10 g), liquefaction is possible to occur according to the initial judgment of the current standard, and the reexamination is needed; the sand dam engineering belongs to an earthquake dynamic peak acceleration 0.05g area, according to quality control indexes (earthquake subarea control indexes in the local area, a standard penetration hammering number method Ncr is 7, and a critical relative density (Drcr is 65%), when fine sand is re-judged during construction and filling, penetration detection sampling positions are randomly determined layer by layer, a penetration number (N) is obtained, if N is greater than 7, the requirement is met, liquefaction is avoided, otherwise, the filling is unqualified, and the filling needs to be further compacted, when the sand dam foundation is a shallow natural silt fine sand body, penetration tests need to be carried out on different positions of topographic relief, and when the requirement is not met, foundation treatment measures such as prepressing, forced ramming drainage consolidation and the like need to be taken.

Because this sand dam belongs to test research nature, the utility model discloses to the liquefaction of antidetonation design sand earthquake take to avoid saturated fine sand earthquake liquefaction measure, the sand dam is filled and is played forbidding construction blasting when about 50% dam height, the prevention arouses the sand dam to receive strong vibrations liquefaction to take place, level sand ovum layer drainage overflow area is laid in dam waist packway position, in order to accelerate formation internal saturated water discharge passage of sand dam, reduce the saturated sand scope, toe sets up the drainage arris in the dam in addition, the construction period upper reaches distribute and hold the interval incoming water of upper reaches (be favorable to the sand dam to increase when filling prepressing loading, drainage consolidation natural fine sand ground process) also play and reduce the same effect etc. of sand dam body (or natural siltation fine sand ground) saturated sand height.

5. Benefits of sand dam immigration protection engineering

The technical scheme has the advantages of small engineering construction interference, wide operation surface, easy comprehensive spreading for construction and simple technical operation, is suitable for local rural immigrants to participate in construction, put into labor and put into work, relieve people with work, increase economic income, make up for the loss of land acquisition and immigrants in reservoir construction, and ensure that vast rural immigrants in construction symbol areas share the dividend of national construction economy development earnings at an early date.

The technical scheme is that the direct engineering investment of the sand dam only accounts for 39% of the investment of a grouted stone compared dam type scheme, the grouted stone compared dam type scheme has small section, narrow construction surface, much construction interference and large excavation amount, particularly, foundation excavation below the water level of a whole year needs to be carried out, underwater excavation amount accounts for 7% of the total excavation direction, meanwhile, measures such as interception and seepage prevention, cofferdam foundation pit, electricity conservation and water pumping need to be carried out, the labor intensity is high, the influence of seasons is prominent, intensive commissioning work is not facilitated, the engineering progress is rapidly promoted, the construction quality of a grouted stone body is difficult to control, construction safety control factors are more, a damming material can not be utilized on site, a main damming material needs to be transported remotely, even a special material transportation channel needs to be built, the mountain blasting stone mining controlled factors are more, the engineering smooth progress management level is higher, and the width of the top surface of the grouted stone is not enough, it is not favorable for replacing the bridge with the dam, and the recovery of the land transportation function at the two sides of the stream river mouth is restricted.

Aiming at the important and sensitive town objects influenced by reservoir inundation, the sand dam engineering adopts the arrangement scheme of the sand dam local immigration protection engineering, resists flood of the foreign river reservoir area, recovers the functions of the protection object waterway wharf, logistics storage, business service, administrative center and the like, enables the local arrangement of a large number of land seeking and immigration to become the best option, creates conditions for the two-industry development and the three-industry development of wasteland utilization and fish culture in a bay, wetland tourism synthesis and the like through the control effect of the sand dam on the external river water level, simultaneously enables land traffic on two sides of the river mouth influenced and interrupted by reservoir inundation, and recovers the functions due to the construction of the connecting path on the top of the ultra-wide sand dam.

According to the technical scheme, the direct engineering investment of the sand dam only accounts for 15.86% of the direct investment of the scheme of moving the towns far away, and if the sand dam is not built, the traffic function recovery cost of two sides of a stream river mouth needs to be additionally invested, so that the comprehensive economic advantage of building the sand dam is more prominent, the effects of 'flood defense, dam bridge replacement, citizen safety and promotion and towns collection' are achieved, and the social and economic benefits are obvious.

Other parts not described are prior art.

According to the utility model discloses a description and the attached drawing, the technical staff in the field makes or uses very easily the utility model discloses an adopt natural siltation gradation bad fine sand to build the construction method of homogeneity sand dam on the spot to can produce the positive effect recorded in the utility model discloses.

The above is only the preferred embodiment of the present invention, not to the limitation of the present invention in any form, all the technical matters of the present invention all fall into the protection scope of the present invention to any simple modification and equivalent change of the above embodiments.

Claims (10)

1. A sand dam constructed by adopting natural silting graded poor fine sand on site is characterized in that: the sand dam comprises a foundation rock layer (9), a natural sand-gravel layer (10) formed on the foundation rock layer (9), a natural silted fine sand layer (14) formed on the natural sand-gravel layer (10), and a filling fine sand layer (16) filled on the natural silted fine sand layer (14), wherein both the inner side and the outer side of the dam of the sand dam are provided with revetments.

2. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 1 wherein: the slope protection at the outer side of the sand dam is provided with a dam waist berm (18), the slope ratio from the dam abutment (19) to the designed water level (1) is 1:2.5, the slope ratio from the designed water level (1) to the dam waist berm (18) is 1:3, and the slope ratio from the dam waist berm (18) to the toe outside the dam is 1: 3.5.

3. A sand dam constructed in situ with naturally silted poor graded fine sand according to claim 1 or claim 2 wherein: the dam outer side slope protection of sand dam adopts rock block bank protection (13), rock block bank protection (13) include sand cobble inverted filter (131), rubble bed course (132) and dry masonry layer (133) that set gradually from bottom to top.

4. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 3 wherein: a drainage overflow belt (17) is arranged in the waist section of the dam of the outer side protection slope of the dam, the drainage overflow belt (17) inclines outwards, and the outer end of the drainage overflow belt is connected and communicated with the gravel reverse filtering layer (131).

5. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 1 wherein: the outer slope toe of the sand dam is provided with a slope protection foundation (12) which is arranged in a through length mode along the axial direction of the dam, and a deposition area (11) used for preventing the outer slope toe of the dam from sinking and horizontally preventing seepage and paving in front of the dam is formed on the outer side of the slope protection foundation (12).

6. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 5 wherein: slope protection basis (12) take dry masonry structure, need go deep into below natural sand cobble layer (10) top surface line 1.5m at least at the bottom of slope protection basis (12), make slope protection basis (12) whole horizontal straight line elevation level arrangement such as, the top surface transverse arrangement is parallel with sand dam axis (2).

7. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 5 wherein: the width of the deposition area (11) is not less than 30m in the direction perpendicular to the dam axis.

8. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 1 wherein: the slope protection at the inner side of the dam of the sand dam adopts a turf protection slope (20), and the slope ratio from the inner dam abutment to the inner slope toe of the dam is 1: 2.75.

9. A sand dam constructed in situ with naturally silted poor graded fine sand according to claim 1 or 8 wherein: a drainage ridge (21) is arranged at the position of the inner slope toe of the sand dam, and a foot forbidden land (22) is arranged between the inner slope toe of the dam and the soil taking pit (5) on the inner side of the dam.

10. A sand dam constructed in situ with naturally silted poor graded fine sand as claimed in claim 9 wherein: the width of the foot-forbidden ground (22) perpendicular to the dam axis direction is not less than 50 m.

Images